Fixing SONY CDP-XA50ES "File Clr" Amnesia

Fixing SONY CDP-XA50ES Amnesia

Here's another repair documentation. For some months now, my beloved XA50ES would greet me with this message whenever I switched it on:

 

This symptom may appear in a lot of Sony CD players. It is likely that the instructions given here can also apply partially for other models. The basic principle is very similar at least.

A lot of Sony CD players support the "CUSTOM FILE" function which means that the player can store your favourite program for up to 224 separate CDs (in the XA50ES at least, the actual capacity may depend on the model). A CD is recognized by its unique TOC layout, and if a custom file for the CD was created before, that very same program will run once the disc is inserted at a later time.

The custom file information is stored inside the player. If the "FILE CLR" message appears at powerup, this means that the custom file memory was lost which is no concern for most people but a nuisance for many others. And it means that there is a defect in the player that should be dealt with.

Surprisingly, looking up this problem in Google does not reveal any useful result. So it might not be a very popular issue. Anyway, hope that this helps somebody :o)

Back when the XA50ES was designed, flash memory was not available yet so the information is stored in a 64 kByte CMOS SRAM. The exact model is Sanyo LC3564SM-10, advertised with extra low standby consumption around 1µA. Typically, SRAM loses its contents as soon as power is gone. To avoid that, Sony designers chose to supply some standby power from a capacitor that gets charged when the device is on, and holds its charge for some time after the device is switched off.

Older devices would have a battery holder somewhere on the back of the device to provide standby power for the RAM. This caused lots of trouble as usual AA or AAA cells would start leaking sooner or later, anyway much sooner than any internal capacitor.

But capacitors are always the main suspect when a device goes bad after 20 years or so. In this case, we have a high-capacity one (a.k.a. gold cap). It has a capacity of 0.1F which is quite a lot in comparison, especially with respect to its minimum form factor.

In the schematics, it can be found - as expected - in close proximity of the RAM chip IC202. The capacitor marking is C201:

C201, our culprit, in the red circle.

So the symptoms clearly indicate that the RAM is not supplied enough power when the player is off. Measuring the voltage results in around 5.5V in powered state, and that rapidly drops to 0V when power is off which proves that the cap is dead.

The XA50ES is pretty service-friendly. We just have to undo six PH2 screws to remove the top cover (which alone outweighs some more modern players!)

All control logic is on the servo board which hangs upside down above the drive. To get to the PCB, loosen another four PH2 screws as indicated here (the screws were already removed when the photo was taken):

Unplug three connectors at the left and four connectors at the right side. You can then flip the entire frame to the back which exposes another three connectors:

 

The black multi-wire power connector at CN91 (near the lower left corner of the PCB) unplugs easily. Please be very careful with the delicate white flat flex cables though (CN101 and CN102). The cables should not be bent sideways or you will risk tearing them. They have a narrow tolerance margin, and spares are practically impossible to obtain, so treat them with respect. To loosen the connectors, gently pull the connector's white tabs towards you which stick out to the left and right side. Try to do this simultaneously on both sides to avoid putting anything askew. The tabs and the lower part of the connector should slide out for a millimeter or two which unlocks the flat flex so you can pull it out of the connector.

We get a first look at the gold cap here, it's this one:

What you can also see is the light barrier that is used to check whether the CD puck is in position or not. The two black plastic pieces near the center of the PCB host an IR emitter and detector. The barrier needs to be interrupted in order for the player to do anything.
Now for the cap, up closer and from the other side:

After removing all cables, unscrew six PH2 screws here to separate the PCB from the metal frame:

Now the solder side of the PCB is exposed, and we can remove C201 safely.
I was a little disappointed to find this side of the PCB looks pretty crusty, unlike the side with the optical components which is totally clean. Functionally that's no problem but they could have considered cleaning up the entire PCB.

Be sure to remember the polarity of the original capacitor. While it appears standard that the top contact that wraps around the side of the capacitor is the negative terminal, your replacement might be different in some way. Caps don't like reverse polarity so better be sure to get it right in the first attempt.

While C201 looked fine on the top side, we need to thank gravity that the cap is usually hanging upside down. That way, the corrosive stuff it spilled didn't reach the board. Actually the PCB looks like it has not had any contact with it. Lucky!

So yeah, that's ugly

To find a good replacement, let's take some measurements:

We could afford up to 15mm in height (higher components would collide with the rotating CD). The old cap took about 4.5mm in height.

The pin-to-pin distance is 11mm

The diameter is approx. 11.5mm

I found the Panasonic EECS0HD224H is a good replacement here. It has the same maximum voltage (5.5V), takes 6mm in height, has the same pin distance as the old one and a smaller diameter. And even better, it has more than twice the capacity (0.22F instead of 0.1F) so chances of losing file data is reduced, too. Plus it's quite affordable at 1.19€.

Panasonic GoldCap vs.the leaky Elna 0.1F cap (above)

 It's a little out of center regarding the silk screen due to slightly different dimensioning but who cares.

And that cured it! The "FILE CLR" message appeared again after the repair of course, not much of a surprise though. After giving the cap a minute to get charged, another power cycle reveals that the custom file function is back working and "FILE CLR" no longer appears! Cool.

Reassembly steps:

• join the PCB and the metal frame back together. There is only one way everything fits. If it does not appear to fit in the first attempt, compare the pieces to the photos above. Eventually secure the PCB with six PH2 screws
• position the unit in the same arrangement as when you dismounted it (flipped upside down)
• plug the power connector (CN91) first and route the wires through the cable holders at the back of the PCB so they are out of the way for the next step
• slide the white flat flex cables back into the connectors. For each of the cables, do this:
• Ensure that the lower part with the tabs on its sides (which you pulled out to loosen the cables) is still in the "pulled" position, otherwise it is hard or even impossible to insert the cable
• Be sure to keep it horizontally level and hit the slot properly so you don't accidentally push the cable under the connector
• The cable should slide in with little force until the metal conductive stripes are almost completely inside the connector
• At some point you will notice the cable is at its end stop when the cable's metal contacts are exposed by no more than ~0.5mm. The cable cannot be pushed in so far that the metal contacts are no longer visible so that exposure is okay
• Ensure the cable is not at an angle, then push the white tabs back towards the connector until they lock in their end position
• I found it helpful to tack the cable to the board in its end position with an adhesive strip across it so it does not slip out when you have no hand free to hold it. That way, you can direct all your attention to closing the connector
• Eventually, gently pull the cable to ensure it is fixed properly. It should stay where it is of course.
• put the metal frame into its original position and secure it with the four PH2 screws
• plug in three connectors (blue, white, red) at the left side. Remember the cable that ends in the white small connector comes from the right side of the unit, and should be routed around the back of the frame, using the same cable ties that also secure the power wires
• plug in four connectors (small white, white, red, white) on the right side. If you cannot find the small white connector, it might be buried somewhere. It is connecting the optical digital output to the servo PCB so if you start tracing it at the TOSLINK port, you will easily find where it ends

Hope you enjoyed this, and good look for your own repairs!

Cheers,

Joe

Final Words

Some legal stuff because you never know: please bear in mind that I am writing this as a hobbyist, not a professional. I describe personal ideas here which is only one of many ways such a repair can be achieved. I cannot guarantee that following this guide will lead to a good result, and cannot be held liable for any personal, physical, or monetary damage anybody suffers by following this guide.
I am open to advice if anything described here is wrong or can be done better. Please let me know in the comments if you find there is anything left to be desired.
Thank you!

Logitech / SlimDevices Squeezebox Classic Display Replacement Guide

Squeezebox Classic (v3) Display Replacement Guide

Hi folks! With the Squeezebox Classic 3, a rather rare item was here today for a display refreshment. I'd like to share the experience with you of course.

Please take a look here for general information on VFDs and what is their problem.

If your Squeezebox Classic display has faded or has shadows, you've come to the right place.

An example of what I mean:

Or even worse:

You'll see the new display in comparison later.

 

Tools Needed

What you need for this repair is:

• a T10 torx screwdriver
• a spudger or flat but stable piece of plastic to remove adhesive pads
• Noritake MN32032-type VFD glass module (MN32032A is current)
• desoldering station (~ 320 °C, no more than 60W) and leaded solder
  
• soldering iron with fine tip (~ 285°C, no more than 40W)
• isopropylic alcohol (95% pure or better) to clean things up
• recommended: 3M 08984 adhesive remover  

 

Tools Not Recommended

The solder pads on the main board should get as little stress as possible. So they should not be heated too much or they will easily come off the board, adding a completely new level of difficulty. So please use temperature-regulated soldering equipment, the reliable / expensive sort if possible.

I do not recommend using solder wick to desolder the old display. It takes too long and will not completely remove the solder in order to loosen the display.

When it comes to cleaning, avoid paint thinner or any other stuff that harms plastic surfaces. It is probably no good for the mainboard, too.

 

Disassembly: Open the Case

Remove the two screws indicated here:

 

You can remove the front piece of the housing now, if it didn't fall off already. Beside these screws nothing holds them to the back casing but you may need to pry the gap between both halves a little.

What you are going to see: the display in its full glory, the IR receiver diode, and a row of connection pins.

Please take a second to check the inside of the front cover. It is typical that it collects a very fine dust on the inside due to static charge. If you move your finger, or a cloth, over the surface, and it is then grey or even black, some dust has accumulated. It causes the display to appear milky so it should be removed for the desired like-new experience.

What you may also see is that people before you have tried to remove the dust. I would say that was not a perfect improvement though. The dust is gone but the surface is full of thin scratch marks:

Again, this photo is from is the inside of the display cover. It may look similar on the outside though.

Be aware that we are dealing with plastic here, no glass, and the surfaces are absolutely delicate so if you go off and clean it, use the softest materials available. We will come back to this later.

 

Disassembly: Loosen the Mainboard

Undo these four TX10 screws indicated: After that, a slight push on the connectors at the back of the device is all you need to get the board out of the case completely.

A quick view of the back side of the mainboard: 

Now, similar to what you can find in the Boom repair blog, you will have to follow these steps:

• desolder the display (18 pins, 2mm spacing)
• cut the adhesive pads beneath the display

 

Desoldering the Display

To desolder the display pins, my recommendation is you use a quality vacuum desoldering station. Alternatively, you may try one of the manual one-shot vacuum pumps but it's considerably more work. As the old display isn't worth anything, you can also cut all its connections with a side cutter, then get rid of the display, and eventually desolder each pin one by one. You will still need to free up all the 18 holes one way or the other to put the new display in.

While in the Boom repair guide I tried to explain how to desolder with a vacuum station in pure text, I have created a video here that shows the desoldering process on the Classic: https://www.youtube.com/watch?v=XDod-obw6Iw

Once the display pins are free, we can go ahead and remove it entirely.

First off, the display is stuck to the mainboard with two adhesive pads, one on each side. Luckily there is just the flat PCB surface directly under the display so there is little risk of damaging components. Still, there is no need to be careless. Some traces hide under the display and they should not be scratched.

Use a spudger with a sharp edge to cut through the adhesive pads on both sides.

 

Viewed from the side; observe how the spudger is slightly bent and the cutting edge stays close to the glass, not the board (to avoid accidental damage to PCB traces):

See here the remains of the adhesive pads once the display is out:

I can totally recommend the following to remove the pads. Isopropylic alcohol will do it but more slowly. The 3M chemical is a powerful agent that softens up almost any sort of adhesive:

You'll probably have a lot of trouble removing the pads without a solvent. While it is not vital to clean it up perfectly, why not take the time?

Using the 3M stuff is easy. Just soak up the remains of the adhesive pads and give it some minutes to do its magic. Soak it up another time and let it sit for a minute. After that, the pads can virtually be pushed off from their position even though I would advise you to pull them off to avoid smearing the adhesive remains.

And there will be some remains once each pad is gone. The adhesive layer is still there but now you can wipe it up with a cloth. If need be in multiple steps, and with another application of 3M. Eventually clean everything up with Isopropyl Alcohol.

The result rewards you with a board good as new:

 

Putting the New Display

The adhesive pads mainly serve the purpose of keeping a little distance between the display and the board (about 2mm, I would guess), and ensuring that the display cannot move. You could set the new display flat on the mainboard with no distance at all, and use double-sided adhesive tape to secure it, however, that spacing might make sense, so this is a nicer alternative:

This is basically double-sided tape with a foam layer in between. It is available in all shapes and sizes and thicknesses. Try to find one that has about the same thickness as the original pads. Craft shops are usually full of them, otherwise eBay or Amazon might be your source of choice.

Before you put the adhesive pads down, please exercise placing the new display. Its 18 pins need to go straight into the holes, none of them should be stuck anywhere. If that works out, stick it down with as many adhesive pads as you desire.

Now we can start soldering the pins. After you soldered the first three pins on one side of the display, take a look at it from the side to ensure that the distance between board and display will be the same on both sides. Therefore, it is best to solder down the other three pins on the far end before turning to the twelve pins in between.

Logitech's production process is mostly automated but the display was hand-mounted. You can see that from solder flux residue around the pins of the old display. As it is likely that your solder wire has flux built-in, more flux will accumulate. Besides looking ugly, it may also be pretty aggressive to the board so my recommendation here is to remove it all after you are done soldering. Isopropyl is ideal here again, best combined with a toothbrush.

With little effort, you can make it look like this:

Please inspect your work carefully. The outer sets of three pins may be shorted. That's not a problem because they have the same potential anyway. Check the other pins, too.

If you have a multimeter or other means of continuity checking device, use that to ensure that each pin is a different potential than its neighboring pin(s).

 

Here is what these pins are, it may help you determine pins that may or may not be connected to each other, and the expected operating voltages:

Pin/group	Specification	Typical voltage range	Description
1..3	F1	+5V DC	Filament Voltage 1 (block of three pins on the extreme left)
4..5	NC		Pins left out (not present) to separate filament voltages from other signals
6	VDD2	+55V (!)	High-voltage rail for grid. Be sure not to touch this pin or accidentally short it to any other pin
7..8	VSS (GND)	0V	Digital ground (these two pins are internally joined together)
9	VDD1	+3.3V	Digital supply voltage for internal circuitry
10	BLK	unknown	Display blanking input
11	LAT	unknown	Data latch control
12	GCP	unknown	Tone control pulse
13	SOUT2	unknown	Serial data output 2
14	SOUT1	unknown	Serial data output 1
15	CLK	unknown	Shift register clock
16	SIN1	unknown	Serial data input 1
17	SIN2	unknown	Serial data input 2
18..79	NC		Pins left out (not present)
80..82	F2	1.4V to 3.9V	Filament Voltage 2 (must be lower than F1, in the block of three pins on the extreme right)

Once that is done...

Testing time!

For the first test, I left the board outside of the case so I could quickly intercept if anything goes bad. Greeted with a logo so bright it is almost blinding:

Nice! Putting it all back together is basically doing the disassembly in reverse. 

But while it's still open, you may consider to review the SMD capacitors. If the SB3 appears to become unstable, for instance reboots when playback starts, or reboots multiple times before it can be used on powerup, you may want to check the SMD replacement guide here: https://joes-tech-blog.blogspot.com/2018/11/logitech-slimdevices-squeezebox-classic.html

Don't forget that the four shorter TX10 screws are the ones fixing the mainboard inside whereas the two longer ones are applied from the back of the device to hold the front piece of the case.

Finally:

Taking a look at the poor little old display, I noticed a considerable amount of burn-in! See how you can easily read (German) text here?

So that display had the worst form of aging. The pixels covered by the text have burnt so bad they actually went darker than the surrounding ones.

It probably sat around uninterrupted for years, just showing the first step in the setup process. So that Classic wasn't even used most of the time. Why the owner had it plugged in at all remains a mystery.

 

Advice for VFD Display Maintenance

If you like to get more information about VFDs and how they are best treated in operation, you may want to read this article. It discusses failure scenarios and also some advice how to avoid damage in the future.

Final Words

I hope you liked this guide.

If you want to have this repair done for your Squeezebox, feel free to contact me. I am available as JoeMuc2009 in the US-based SlimDevices Forum, or  as JoeMod2015 in the German Squeezebox Forum. Or just drop me a note here in the comments. Or contact me via e-mail to johannesfranke74@gmail.com.

I have collected experience with Squeezebox devices for some years now and can fix more issues than just the displays. Always glad to help so don't hesitate :o)

Cheers,

Joe

 

Legal Concerns

Some legal stuff because you never know: please bear in mind that I am writing this as a hobbyist, not a professional. I describe personal ideas here which is only one of many ways such a repair can be achieved. I cannot guarantee that following this guide will lead to a good result, and cannot be held liable for any personal, physical, or monetary damage anybody suffers by following this guide.
I am open to advice if anything described here is wrong or can be done better. Please let me know in the comments if you find there is anything left to be desired.
Thank you!

Logitech Squeezebox Boom VFD Display Repair Guide

Tired of seeing this?

No question, the Squeezebox Boom is a fabulous device. However, some small mistakes in the design as well as in the documentation make it susceptible to some annoying symptoms of aging, becoming apparent by a shadowy / fading display, or the display showing nothing at all any longer.

What happened? 

To make it short: we have a mix of aging of the display itself, plus aging of the power supply circuitry. Both lead to faded or completely dark displays.

Edit 2020-06-08: more details on this can be found in this new blog post: https://joes-tech-blog.blogspot.com/2020/06/vacuum-fluorescent-displays-how-they.html

The Squeezebox Boom, like many other devices of the Squeezebox series such as Transporter and Classic, employs a Vacuum-Fluorescent Display (VFD) for user interaction and entertainment. Look here for more info: Wikipedia.com

Why VFDs?

VFDs are kind of old-school today. Most people know them from (older) table calculators, cash registers, video recorders, dash displays in cars, etc. Their main advantages are that they are pretty bright and fast. There is hardly any "lag" when a pixel is switched on or off. They are much better in this respect than LCD displays. They emit a bright cyan/green light which can be easily modified with filters to grey, green, orange or whatever.

I think Logitech chose VFDs because they simply look good in operation. As the Squeezebox UI uses a lot of animations and visualizations, VFDs are the displays of choice for this kind of application.
Logitech picked the Noritake MN16032 glass module and implemented the driver themselves. So what you need is a MN16032, not one of the GU160x32 modules that Noritake is selling as well. The GU series is basically the glass module mounted on a PCB with some microcontroller and power supply. The Boom contains all of this.

Edit from 2017-06-19: Noritake Itron is updating the MN16032 to a new revision. The previous one is the MN16032G, the new one is named MN16032GB. You can purchase any, both will do.

One main disadvantage of VFDs is that they are aging, just like old cathode-ray tubes (CRTs known from TVs), or plasma displays. The phosphor coating of a pixel burns up over time while it is on. The speed of decay is determined by the time the pixes is on, and its brightness. The longer and brighter a pixel shines, the faster it will fade. So aging is no issue when the display is completely blank.
The outcome of permanent content creates ugly artifacts such as these, from a display that actually shows "all pixels on":

Some static text has been in the same place for a very long time. It has burnt in so much you can read the shadow of something like "RDSI: 19,392Mbps" in the third line. The text in the bottom line seems to have varied but not really much as there are clear shadows of M, H, D and T characters.

How does Logitech make it worse? Screensaver!

This process cannot be stopped except by not using the display at all. But things can be improved by limiting the maximum brightness of the display, and not using what Logitech prefers to call "screensavers". Because these actually do the exact opposite. A permanent display of the clock time or the current weather will lead to partial fading of your display. That's not what I would dare call a screensaver.
Moreover, the clock time is displayed in the same place all the time. It does not "wander around" on the display to make use of many different pixels and use them up equally. As a result, most Boom displays fade in the center first. The photos above show how bad this can get. It is clear to see that the shadows four large digits exist where the clock time usually appears.
Generally I accuse them of not mentioning the risk of VFD aging anywhere in their documentation. It's a shame but the people responsible for the documentation probably weren't aware of the problem at all.

Automatic Brightness and Why I Don't Like it

Besides destructive screensavers, Logitech screwed up the automatic brightness behavior. While it is possible to set a minimum brightness and a sensitivity, it is not possible to specify a maximum brightness. And in my opinion, the sensitivity is a bit too far on the high side even on its lowest setting, i.e. the display is at the highest brightness most of the time.
Imagine you have a Squeezebox Boom on your bedside to act as an alarm clock. Sure you want to see the clock time at night, but what about daytime when you are at work? Daylight will cause the automatic brightness control to drive the display at its maximum capability, without anyone even looking at it. I think that is how most displays suffered from premature aging, while nobody cared.
So my recommendations to increase the life expectancy of your displays are:

• don't use automatic brightness. Set a fixed brightness as low as possible
• never exceed brightness level 3 (out of 5)
• in standby, do not have the display show a clock time or anything else that resides in a static position on the display

Many people will now think that these measures render their Boom useless. Well, this is just if you care more for the display life than for your personal comfort. There is still a chance to replace burnt-out displays. That's what this guide is all about.

VFD Filament Power Supply Design Issue

Unfortunately, there is also a design flaw in the Boom concerning the filament power supply. The filament wires are directly behind the front glass. In dark environments, you can see them in the form of six horizontal glowing lines. The Boom VFD has a filament voltage of just 5 Volts on the left and approx. 2 Volts on the right side of the display, but a current of up to 2 Ampères! The supply circuitry consists of SMD components so small they are hard to see, and they run almost red hot. I have measured 100°C and more. Here is a picture taken just after powering on a mainboard, showing the top-right edge of the board. Behind the display there is at least one transistor, MOSFET or something that heats up pretty bad:

It is likely that one of these components causes the lower of the filament voltages to become unstable which causes the display to look ugly, to fade, or to go dark completely. I have found the following symptoms so far:

• right display voltage ramps up to as much as 5.5 Volts after the PSU is connected. The display initially looks good, then begins to fade. The comparatively high voltage on the right means there is no more voltage drop across the filament which causes the electron emission to stop
• right display voltage is 0 so the circuit is open. No electron emission can take place then

EDIT 2017-05-01: there is a fix available for the former symptom! See here

The left side of the display is constantly supplied 5V. I think the left side is more or less directly connected to the main power supply whereas the right side is sub-regulated, and that regulation circuitry fails.
The hobbyist in us immediately assumes that there are electrolytic capacitors involved which evaporate their electrolyte over time, especially in warm environments. Known issue with tons of old electronic devices, but not in this case. As far as I can see, the circuitry around the display voltage generation does not use electrolytic caps.
Logitech does not make technical documentation for any Squeezebox device open for now, so it is hard, if at all possible, to find out what is the failing component.
There is one more thing to say about Logitech's mistakes: many Boom owners will have noticed that their Boom is pretty warm all the time, even if the unit is in standby and configured not to show anything on the display. This is due to the fact that the Boom keeps the VFD filament powered all the time! Even if nothing is shown on the display and the unit is in sleep mode, the filament power circuitry, besides some more components inside the boom, is constantly powered. Eventually you can switch on the Boom anytime through the Squeezebox Server UI, an app, the IR remote etc. so it needs to be aware and keep parts of its control logic running, e.g. the IP interface, the Wi-Fi board. But is is clear that Logitech did not focus on power saving whatsoever. I assume that the difference between standby and "on" is absolutely minimal. Maybe the power amplifier that supplies the speakers is really off during standby. Everything else is fully powered. That's why the Boom is instantly ready when we tell it to do anything while it is standing by.
This is a thermal picture of my Boom after 6 hours of standby with nothing on the display at all:

The constant "need" to supply the filament voltage surely adds to the aging of the circuitry.
By the way, the filament itself does not contribute to the display aging. While it's a shame the filament is always powered, the display just suffers if pixels are on. So the main concern here is waste of energy.

Tools Needed

What you need for this repair is:

• a T10 torx screwdriver
• a spudger or flat but stable piece of plastic to get off the grilles and remove adhesive pads
• straight pliers
• Noritake MN16032-type VFD glass module (MN16032G is current)
• desoldering station (~ 300 °C, no more than 60W)
• soldering iron with fine tip (~ 285°C, no more than 40W)
• isopropylic alcohol (95% pure or better) to clean things up
• recommended: 3M 08984 adhesive remover  

Tools Not Recommended

The solder pads on the main board should get as little stress as possible. So they should not be heated too much or they will easily come off the board, adding a completely new level of difficulty. So please use temperature-regulated soldering equipment, the reliable / expensive sort if possible.

I do not recommend using solder wick to desolder the old display. It takes too long and will not completely remove the solder in order to loosen the display.

When it comes to cleaning, avoid paint thinner or any other stuff that harms plastic surfaces. It is probably no good for the mainboard, too.

Boom Disassembly

Steps to get down to the mainboard:

1. remove the speaker grilles (left and right)
2. unscrew the control panel, four T10 torx screws (one in each corner)
3. pull the control panel flat flex cable
4. unscrew the mainboard, five T10 torx screws (one in each corner and one in the center)
5. pull the mainboard out

Disassembly: Remove the Speaker Grilles

The grilles are attached to the case with rubber-covered tabs. I recommend using a flat spudger that can be pushed in between the outer case rim and the grille. Take care here because the outer case rim is thin shiny plastic so it is very delicate. You may easily leave marks there that look ugly ever after. So be very gentle and take your time.

Once we're in, lift the grille a bit but do not try to remove it completely yet. Do not use the case rim to crank the grille away because that might ruin the look.

The same needs to be done on the other end. There are also fixing tabs on the outer edge of each grille but they will give way once the upper and lower edge are free.

Eventually this is what you see:

Disassembly: Loosen Control Panel

Next level: let's undo the control panel because it is in the way later. First undo these four TX10 screws:

Disassembly: Undo Control Panel Flat Flex and Remove Control Panel

Once the control panel is loose, be aware that there is a short flat flex ribbon cable in the bottom right corner that needs to be loosened on one of its ends. I find it easier to remove the mainboard-side end of it. This is what you will see when you lift the control panel (gently!)

Edit 2022-05-04: The flat flex cable (FFC) has the same style of connector on both ends. Both connectors are facing upwards, so that is the direction that the FFC needs to be pulled out of the connector. I find it easier to disconnect (and later reconnect) the front-panel side, because there is just more room for doing so, and leave the mainboard side connected. Do keep in mind that the FFC does not like to be connected and disconnected a lot, sooner or later the metal strips will detach at the connecting end(s) and that can cause all sorts of trouble.

NOTE: be sure to just pull the cable out of the connector. Do not rip the entire connector off the board! Because: https://poetnerd.blogspot.com/2020/08/squeezebox-boom-microsurgery.html?showComment=1611480568539#c8879436387643920068

So please make sure not to pull the flat flex any other direction than directly away from its connector, opposite direction of how it was plugged in - and just move in parallel to the board. If you pull upwards away from the board with too much force, you may lift the connector or tear the cable.

Disassembly: Remove Mainboard

With the control panel gone, we see the mainboard in all its glory:

Loosen five TX10 screws in these positions. They are the same length as the four we have already removed earlier. Keep in mind the positions and orientation of the two metal tabs beneath both the top screws:

The ribbon cable in the top-right corner connects the snooze buttons at the top of the device. Pull it out gently towards the Boom's front side as shown here.

The mainboard won't come out easily because the speaker connector on the back is still plugged in. It is positioned behind the left side of the VFD display.
To remove the mainboard, push the backside connection panel inwards, thereby lifting the mainboard. It is recommended to push the right edge out first because of the speaker cable that prevents you from pushing the left edge out as easily. If you feel that nothing is moving, there might be glue between the backside of the board and the case. That is because Logitech production did not have the time to wait for the glue to cure before mounting the main board. Be extra gentle then. Keep pushing with as little force as possible. The glue should tear off eventually. If you are too violent or do this too quickly, the SMD components on the board which are covered by the glue might be torn away.

A little more room can be made by lifting the board on the right side, then pushing it to the right a bit until its left edge can face towards the backside of the case as shown here:

Eventually here is the speaker connector, with the right board edge pointing 90° away from the enclosure. It's a really firm connection and the wires are pretty short so there is not much room to work:

I recommend the pliers to pull the plug out (away from the connector). If that does not fully succeed, you can also try to pull the entire board away - but well-controlled, please:

Preparing the Mainboard

Now that the board is out, we need to take a few steps before the VFD can be desoldered.

First the Wi-Fi antenna that is stuck to the board at the top edge needs to go. It's the metal tab at the bottom edge in the following picture:

Why it needs to go? Because the sticker covers three of the display pins we are going to desolder:

So lift the black tape gently. Make sure you do not bend the antenna:

The antenna is usually glued to the black strip with another black adhesive foam pad which won't come off in one part. So at the bottom of it, you will find remains of the pad which I recommend to remove completely to make way for a new pad:

We will have to scrape down layer by layer. Beneath the foam, a tough layer of adhesive comes up:

This is where 3M 08984 makes things really easy. Just cover the entire pad multiple times and let it dissolve the adhesive. You can also use isopropylic alcohol but it will take more time.

One more layer of adhesive comes off now:

Eventually some spudger work removes the last bits of the adhesive, leaving only the metal. A Dremel will also do nicely. The surface will get scratched on the way but that does not do any harm. The antenna is still going to work as it should. Just ensure that the surface is clean so the new foam pad can hold it properly.

The black plastic strip probably left a paper-like layer on the board. Use adhesive remover or alcohol again to remove what is left:

Later:

Besides the three display pins we just uncovered, there are 15 more pins on the other side. All of these need to be desoldered:

You might find that Logitech has put some glue right on top of the display pins to tuck down the antenna cable. That's unfortunate because that glue is really tough. If you find something like this:

or this:

...be prepared for some extra hours. The upper picture shows a rather mild extent of the problem where only a fraction of the glue blob covers the soldering spots. The lower is rather extreme with at least five pins being completely covered and in need to be excavated.
In this state, it is rather easy to remove the antenna wire. Just perform a careful cut beneath the black wire into the glue material to create a slot through which you can push the antenna cable out sideways. It should not be in the way during soldering anyway.
The problem is that you cannot rip the glue off the board because there is a high risk you will tear off the SMD components to which the blob is firmly stuck. It won't come out as one piece and is potentially stronger than the adhesive that links the soldering pads to the main board material. You will need a sharp blade of some sort, and make sure that you do not touch the mainboard while cutting through the glue blob because you might easily damage traces or SMD components. Violence is definitely not an option here. "Shave" off the blob carefully, layer by layer, until the pins you want to desolder are free.
So far I found that the glue resists high temperatures so you cannot melt it. It will turn black but not go away. It will get a little bit softer though. Dissolving it with some chemical might work but my attempts with 3M adhesive remover and isopropyl alcohol were miserable failures as they changed nothing. So it comes down to a spudger or a blade and tons of patience. You must never slip because cutting any vias on the PCB might come out fatal. I have honestly spent hours with that, which is still better than doing this in a rush and creating yet another brick.
Once the display is out, the surface of this area is flat and thereby easier to work on to remove remaining glue.

Removing the Old Display

The display glass module is stuck down to the mainboard with three adhesive foam pads. You can see two of them at the lower edge of the display. Right edge:

And left edge here:

The third pad is hidden beneath the top edge of the display and is very hard to reach.
You can find the foam pad positions in the pictures coming up.
What is also important to note is the black strip on the upper edge of the display. The purpose of this is to protect the ambient light sensor (you can see it a little to the right or the center in the next picture) from picking up the display light which would distort ambient light measurements and confuse the automatic brightness circuitry, if you ever use that at all (again, I don't recommend it but it's still everyone's own decision).

Remove this strip and keep it for the new display.

Before desoldering the display, let's detach it from the sticky foam pads. I recommend a sharp blade or spudger. Be sure to stay as close as you can to the glass. Do not try to cut the foam pad anywhere closer to the mainboard because you will probably damage or even rip off SMD components hidden beneath the display.
The critical places are shown in the following picture. The display was already removed before, and the top side of the board is actually facing down on the photo. You can see the foam pads (left/top, center/bottom, and the black one right/top) as well as places where SMD components are in your spudger's way potentially:

So again, stay on the glass side when you cut the pads! It's really vital.

Also take care to stay in line of the foam pad. The next picture illustrates how you might accidentally hit an SMD component on the way if you don't stay under the display. As cutting through the foam pads requires some force, you might easily slip or break things. Be gentle and controlled, and take your time for this.

The third foam pad needs to be cut "blindly". Just push the spudger in so it touches the glass and is as far as possible from the PCB. Now that the black tape that protects the light sensor is gone, you can get a good view from the top edge while you cut the pad.
Eventually, the display should come loose like so:

Desoldering time. I recommend using a vacuum desoldering station set to ~300°C with a 0.8mm tip. There is one SMD capacitor that is quite close to the first three pins as shown here:

Try to work around that capacitor. Its plastic base may melt a bit, that's no problem. But try not to bend the capacitor as that would cause a considerable stress to the SMD pads it is soldered to. It can't be good if you happen to snap it off along with its solder pads.
It is hard to show here but I found desoldering easier when the display faces upwards, mostly because you can easily see when a pin is moving free, indicating that all solder around it is liquid and you are ready to remove it. So for each pin, I do this:

• hold the board with the display facing down
• put the desoldering nozzle on the pin to be desoldered
• flip the board around, keeping the nozzle on the pin (nozzle now points upwards)
• keep the nozzle in place until the solder liquefies
• wiggle the nozzle around the pin. The display pin should move accordingly on the top side of the board. As long as it doesn't, stay where you are (should only take a few seconds, otherwise something else might be wrong)
• activate vacuum and keep wiggling while the solder is being sucked away. This ensures that the pin is free afterwards and does not solder itself back anywhere
• if a pin cannot be desoldered, add some fresh solder with a soldering iron, if need be, on both sides of the board. Make sure the solder was liquid on both sides of the board, then retry desoldering

After all pins are desoldered, move each pin to ensure they are all actually free.
An alternative approach is to clip all display pins first (you are probably discarding the old display anyway), then get rid of the glass module and desolder each pin separately. Might be easier because you can then use pliers to pull the pin whilst desoldering it.
Once the display is out, check against a light source. All 18 holes should be free now. If any is clogged, use the soldering iron again to fill it with fresh solder, then remove it all with the vacuum station.

Mounting the New Display

So this is where we are now:

Depending on the state of the foam pads, we can reuse them by putting double-sided sticky tape on top of each like so:

If the foam pads are in a bad shape, feel free to remove them. It is a time-consuming piece of work though. Keep in mind that there are SMD components covered by some parts of the foam pads so you cannot use a metal spudger here. Instead, you will have to use adhesive remover, something soft (plastic spudger, Q-tip, whatever) and a lot of patience again.
The foam pads should be replaced due to the delicate nature of the glass display. It should be stuck down somehow or the display will experience vibration and its pins might wear out sooner or later. So if you removed the pads, try to obtain new ones as close as possible to the specification of the ones you just removed. The thickness is about 2mm, and each is about 30mm x 6.5mm in size.

Apply the black tape to the new display. If needed, use double-sided tape if the adhesive stayed with the old display:

Carefully position the new display on the PCB. Align the pins so they are in a row and have equal spacing between all pins. Insert the pins into the soldering holes, then, while keeping a safe distance from the sticky foam pads, use the white frame that is printed on the PCB to align the display. When you are sure that the position is good, push the display down onto the sticky pads.
Side view before resoldering:

Do the 18 pins, using solder sparingly to avoid shorts. Eventually the pin spacing is only 2mm so using a fine soldering tip is definitely recommended. Do not heat up the pads for too long to protect them from coming off the board.

Final Cleanup

After the soldering work is done, I recommend to remove the flux that is left from the factory assembly of the old display (well, Logitech did not really excel there), and probably also from the solder you just used. Flux is corrosive and some are even hygroscopic which might cause trouble later. Isopropylic alcohol is perfect for removing the flux and won't cause any trouble electrically, plus it evaporates quickly. Use a brush or a toothbrush and generous amounts of alcohol, wipe across the solder pins until the liquid that comes off the board is no longer brown or yellowish but clear.

After cleanup, the site should be nice and tidy:

To reattach the Wi-Fi antenna, I recommend a double-sided sticky foam pad cut to size:

Before you stick down the antenna, ensure that its body will not touch any of the surrounding metal contacts. It should be centered between the contacts next to it in all directions. The following photo shows it between the first group of three pins of the VFD on the left, and the three contacts of the IR receiver diode on the right:

Eventually, the inside of the control panel's screen should be cleaned up so there is no distortion from it. Over the years, the screen collects some fine dust that covers the entire inner surface and might lead to a milky / blurry vision. This is a good opportunity to remove all dirt from it. You may need multiple passes with a soft cloth and alcohol. No worries, there is no coating on the screen. But please ensure that the material you use does not cause any scratches and won't attack plastic surfaces by any means. Paint thinner for instance is sure to ruin the job.
The picture illustrates how smears from a previous cleanup attempt remained and can be seen against light:

These smears will be illuminated by the display and we just don't want that. Just keep on cleaning until all that crud is gone. It will improve the experience even more.

Notes on Reassembly

Verify Everything

As we get closer to the first power-up after the repair, it's time for a full check of our work:

• Check all solder connections for shorts and cold joints. A continuity tester is great for this. The groups of three pins on the left and right side of the display have the same potential so it is okay if they appear shorted. But no neighbors among the remaining 12 pins should be shorted
• If you find that the solder on a pin looks dull, or the pin can still move, heat the connections in question up another time
• If you want 120% safety, measure each display pin against the respective trace on the mainboard to see if any connection is not actually working
• Ensure that the reattached Wi-Fi antenna does not have direct contact to anything

Speaker Cable

As before, there is not much room to move the speaker connector back where it belongs. So place the board with its left edge facing the main board recess in the case so the connector and plug are close together. Then align them and push them together with the pliers. It is very hard to do this by hand. The connector may seem fast but actually it might still be loose, later causing dropouts and distorted sound. If you use pliers, it is much easier. Squeeze until the connection clicks into place:

The speaker cable can be pulled out of the casing by some millimeters which gives you more freedom. But consider that there is not much room to stuff the wires away eventually so keep the wires as short as possible.

Sanity Check

After mounting the mainboard might be a good time to verify the results of your repair progress so far. Even though the control panel is not yet attached, you can power up the Boom. Just observe whether the display lights up bright and shiny after a maximum period of 5 seconds. If it does, see if the board passes the boot sequence. You may use the IR transceiver, the mobile app or the Squeezebox Server interface to play some music for verifying that the speaker connection is intact. If everything works, congratulations! You are practically done. Just unplug everything for the final assembly.
If the display stays dark, you hear noises, smoke comes out somewhere, detach the power supply as fast as possible. Let's just hope this never happens. There is no technical support for that situation.

Mainboard Fixing Screws / Metal Tabs

Make sure you place the metal tabs the way they were before. Note that the top-right metal tab pushes down on the snooze button ribbon cable so the cable must run beneath the metal tab, not across:

Please make double sure that the unit is not powered while you put the screws and metal tabs back in. They are electrically conductive and any shorts on the mainboard are probably fatal.

More Information

You might have noticed that some photos and part of the disassembly / reassembly instructions is familiar. I have copied it from my other blog entry about how to repair the bass woofers of the Boom. See here if you are interested: Bass Repair

Final Words

Some legal stuff because you never know: please bear in mind that I am writing this as a hobbyist, not a professional. I describe personal ideas here which is only one of many ways such a repair can be achieved. I cannot guarantee that following this guide will lead to a good result, and cannot be held liable for any personal, physical, or monetary damage anybody suffers by following this guide.
I am open to advice if anything described here is wrong or can be done better. Please let me know in the comments if you find there is anything left to be desired.
Thank you!