DIY: OEM Alpine Head Unit Capacitor Replacement

I was having issues with my stereo sounding distorted for the first few minutes after it was turned on, and I suspected failing electrolytic capacitors like I found in my SRS unit and my fan control unit. This isn't an uncommon problem, as [MENTION=25737]Kaz-kzukNA1[/MENTION] has repaired several head units with much worse damage than what I found. For reference, he's got a whole category dedicated to fixing head units and amps. I was able to remove my head unit and disassemble it, using the following two videos as reference:

https://www.youtube.com/watch?v=8FoN7BBlJBw&list=PLpY4XKE12KVBQTn1mzz7lbpwDLq1Z6tmD&index=3
https://www.youtube.com/watch?v=5WnN9SiHP1M&list=PLpY4XKE12KVBQTn1mzz7lbpwDLq1Z6tmD&index=5

I'm glad I did, because the once I removed the bottom cover I was greeted with leaked electrolytic which was starting to eat the traces:



I decided at this point that it would be a good idea to go ahead and replace all the electrolytics in the head unit, since multiple caps were starting to leak and little (if any) damage had occurred yet. I would venture to say that this is going to happen to all NSX head units eventually, especially since all the caps were rated to 85°C. It would be best to get ahead of the problem and replace them before damage occurs, since repair of the PCB makes things even more difficult.

With that being said, I made a spreadsheet documenting the value, voltage, and lead spacing for all the electrolytics in the head unit. Over the next few weeks I'll add add pictures of the repair process, for anyone else who wants to tackle this job. I chose capacitors with preference to specs in this order: Value & Voltage, Lead spacing, AEC-Q200 (automotive) qualified, >105°C rating. In only one instance I was unable to find a part that was rated to at least 105°C, which is fine because all the original parts were 85°C anyways. I consulted with some EE's at work and they said it would probably be ok to replace the smaller values with ceramic caps, but some linear regulators and filters may depend on a minimum ESR for stability. I decided to err on the side of caution and choose all electrolytics again.

View attachment head_unit_caps_r4.xlsx
Digikey cart with parts in attached spreadsheet: http://www.digikey.com/short/qpjhbb

Be warned, there are 81 caps in the head unit, not including those in the AM tuner, FM tuner, and cassette player, all of which I negated due to laziness and\or difficulty of access. Keep in mind that my NSX is a 91, and Kaz has mentioned that the values were changed over the years. Additionally, there are several screws that need to be desoldered for the boards to be removed, as well as a ground tab on the FM tuner and the aux antenna lead. Here are some photos of the disassembly process:

After removing the top of the unit, with the top processor board, AM tuner card (second vertical from right) and FM tuner card (vertical at right) visible. I've documented all of the caps in this photo, excluding the tuner cards


Bottom processor board, the location of ~50 of the 80 caps


These three caps that seem to do most of the leaking. I believe they're potted down and only the center cap is leaking


Caps in the AM tuner card that are difficult to get to, and I don't think I'm going to replace


Caps on the FM tuner card which are also not getting replaced. They're not labeled, which would make documenting the process difficult.


Caps in the tape deck which are difficult to get to.

I love the closing lines in the second video "we don't care to see these radios in the shop".

Old Guy said:

I love the closing lines in the second video "we don't care to see these radios in the shop".

Click to expand...

Based on the number of capacitors and the extent of the damage that can be caused by them, I'm not surprised!

I'm thinking I should replace the caps in the tape deck - they're at the top of the radio and when they leak, it'll drop down onto the top processor board. If the AM and FM cards leak they'll just take out the radio, which might be worth it for all the extra work it would make to replace them.

Thanks for doing this. The case for replacing electrolytic capacitors proactively is strong considering the work involved if any have leaked and eaten through traces, boards, etc.
I have been meaning to get to this for over a year now. Another member on here even donated a head unit to me to get started
time to place an order at digikey.
your documentation is probably good enough for me to get started.

crxguy52 said:

Based on the number of capacitors and the extent of the damage that can be caused by them, I'm not surprised!

I'm thinking I should replace the caps in the tape deck - they're at the top of the radio and when they leak, it'll drop down onto the top processor board. If the AM and FM cards leak they'll just take out the radio, which might be worth it for all the extra work it would make to replace them.

Click to expand...

The only thing to consider is whether a failing capacitor which shorted out on one of the tuner boards could take out the DC power supply disabling the whole head unit. If you don't plan on using the tuners or the cassette (or do you still have some cassettes stored in a carton in the basement?), one option might be to remove the tuners and the cassette board providing that did not create an error condition which disabled the complete head unit.

Hi,

Old Guy said:

(...) one option might be to remove the tuners and the cassette board providing that did not create an error condition which disabled the complete head unit.

Click to expand...

i removed the cassete mechanism and board when i replaced the caps, and sure enough, an error popped on the screen and the headunit wouldn't work... so, i had to get everything back in there

Thanks,
Nuno

I opened up my factory radio a few weeks ago then noped right out of there when I saw that the caps were all still good. But while I have the interior apart I suppose it would be wise to replace them now to make life easier down the road...

In the second video from carstereohelp.com the narrator says that more of these units could be repaired if they had the schematics. Additionally, schematics are available, but only in paper form and in Germany.

Does anybody know who in Germany has the schematics?

I'd love to follow up on this lead, but don't know where to start (and don't speak the language).

warrenw said:

I have been meaning to get to this for over a year now. Another member on here even donated a head unit to me to get started
time to place an order at digikey.
your documentation is probably good enough for me to get started.

Click to expand...

There are only ~11 unique caps in the head unit, I plan on updating the spreadsheet sometime today with Digikey part numbers (might save you some time)

UnhuZ said:

i removed the cassete mechanism and board when i replaced the caps, and sure enough, an error popped on the screen and the headunit wouldn't work... so, i had to get everything back in there

Click to expand...

It was a good idea Old Guy, thanks for the info UnhuZ! What did you end up doing, replacing the caps in the tape deck?

MotorMouth93 said:

I opened up my factory radio a few weeks ago then noped right out of there when I saw that the caps were all still good. But while I have the interior apart I suppose it would be wise to replace them now to make life easier down the road...

Click to expand...

At the very least it would make sense to replace the 3 big ones on the bottom board, these are the ones that seem to leak first (and can do the most damage). Unfortunately I don't think it's a question of of but rather when these will fail.

SWFL_NSX said:

Does anybody know who in Germany has the schematics? I'd love to follow up on this lead, but don't know where to start (and don't speak the language).

Click to expand...

If it helps I could take some detailed photos of the PCB when I do the replacement. I'd imagine the traces on your PCB are eaten away and you need to fly wire them.

Updated original post with replacement parts and digikey cart for convenience.

UnhuZ said:

Hi,

i removed the cassete mechanism and board when i replaced the caps, and sure enough, an error popped on the screen and the headunit wouldn't work... so, i had to get everything back in there

Thanks,
Nuno

Click to expand...

If you only remove the cassette mechanism and short two pins on the board (left in the unit) the rest of the functions are still there (radio/CD). Those two pins tell the Alpine unit that no cassette is in there but I don't remember which two.

Hi,

crxguy52 said:

(...) thanks for the info UnhuZ! What did you end up doing, replacing the caps in the tape deck?

Click to expand...

Nope... only the 2 main boards and a tiny board that i don't recall which is it (i have photos of each of them)

goldNSX said:

If you only remove the cassette mechanism and short two pins on the board (left in the unit) the rest of the functions are still there (radio/CD). Those two pins tell the Alpine unit that no cassette is in there but I don't remember which two.

Click to expand...

Thant is good info Thomas... i intended to remove anything cassete related for weight savings .. as also the chassi... just keep the front panel attached to the console and the necessary boards... but i quited that and just re-assembled everything with new caps on 3 boards (also had to clean tracks/traces on the boards to check for continuity)

Thanks,
Nuno

Thanks for all the work, I placed my Digi-Key order, see how this goes. :smile:

goldNSX said:

If you only remove the cassette mechanism and short two pins on the board (left in the unit) the rest of the functions are still there (radio/CD). Those two pins tell the Alpine unit that no cassette is in there but I don't remember which two.

Click to expand...

Thanks for the info. I'm going to try and keep my tape deck by replacing the caps, there aren't too many and I'm in this far already

warrenw said:

Thanks for all the work, I placed my Digi-Key order, see how this goes. :smile:

Click to expand...

I found a few mistakes in my spreadsheet - there are a few one-off voltage ratings that are higher than the rest. I've updated my spreadsheet in the original post and highlighted them. It's only 4 parts. Additionally, all of the new caps are ~4mm taller. I don't think this will cause an issue but I need to verify.

After ~5 hours of work I'm about 75% done removing the capacitors, I've completed removal on the bottom board (57 caps) and the back interface board (5 caps). I'd say that for anyone considering this, a desoldering station is a must. I had initially considered just using desoldering braid, but it would have been a nightmare. In addition to the large leaky cap on the bottom board, I found at least 5 more leaky caps elsewhere in the head unit (tuner knob board, back interface board, top processor board).

Removing the large caps on the bottom was a pain due to the potting compound having the consistency of bubble gum, but I eventually got them off. The potting compound took off some of the soldermask with it, so I applied some conformal coat to keep the traces insulated. I also verified the accuracy of my spreadsheet as I pulled all the caps off, and so far it's spot on.

What are you guys in the US listening to, UKW (ultra short wave), LW, MW? In Switzerland, UKW was very common but DAB+ is much better, more choice of music, much better quality. Tape is outdated, CD/DVD too. Vinyl has a revival but in the car? UKW is shut down in Switzerland after 2020 and maybe some other countries in Europe too. DAB+ is favored.

What to do with the antique BOSE/Alpine headunit?
- leave it in the car to remain OEM?
- new head unit double-DIN? Not everybodies taste.
- throw it out (stereo delete plate)? I went with this option.

In Europe, if UKW dies it's hard to justify the rebuilt of the head unit.

goldNSX said:

What are you guys in the US listening to, UKW (ultra short wave), LW, MW? In Switzerland, UKW was very common but DAB+ is much better, more choice of music, much better quality. Tape is outdated, CD/DVD too. Vinyl has a revival but in the car? UKW is shut down in Switzerland after 2020 and maybe some other countries in Europe too. DAB+ is favored.

What to do with the antique BOSE/Alpine headunit?
- leave it in the car to remain OEM?
- new head unit double-DIN? Not everybodies taste.
- throw it out (stereo delete plate)? I went with this option.

In Europe, if UKW dies it's hard to justify the rebuilt of the head unit.

Click to expand...

We've got 88 - 108 MHz FM radio here, and as far as I know it isn't going anywhere. There are "digital" FM channels, but they always have a main channel which is still broadcast in conventional FM. This is about the extent of my knowledge of radio standards, so take it for what it's worth. :biggrin:

My hope in all this is to keep at least FM radio and the aux input for a Bluetooth adapter. Those two mediums cover 99% of what I listen to. Even if the FM went out, I'd be happy with just Bluetooth (which wouldn't work if the caps ate the board)

crxguy52 said:

After ~5 hours of work...a desoldering station is a must. I had initially considered just using desoldering braid, but it would have been a nightmare.

Click to expand...

Nice job! What type of desoldering station would you recommend? It looks like there is a wide range of price and features...

crxguy52 said:

In addition to the large leaky cap on the bottom board, I found at least 5 more leaky caps elsewhere in the head unit (tuner knob board, back interface board, top processor board).

Click to expand...

Could you keep track of the caps that are most likely to fail?

Again, love to see this sort of stuff. If the sound quality of this unit can be restored then if you combine it with a bluetooth adapter I don't see the reason to replace...

Lots of different de soldering stations. There are some pretty inexpensive off-brand Chinese vacuum style units that seem to be fairly effective. The EEVblog reviews a lot of electronics stuff and has this review on one popular off-brand station.

https://youtu.be/Ft50m8UU5WQ

The guy doing the review on the ZD985 de soldering station can be a bit of a combination of annoying / amusing; but, he is not stupid and his observations are good. The ZD985 offers excellent value for money in terms of its performance as long as it works when you get it and it doesn't burn your house down. Most of these 'off brand' Chinese vendors sell to a price point and achieve that price point by not bothering to have the product certified by the CSA, UL, TUV or CE and hiring guys just off the farm to assemble them. I purchased an off-brand dual channel lab power supply a couple of years ago. Works pretty well; but, the input was un fused and if you had an internal problem its cleared that problem by having the power supply burn up and then tripping off the service circuit breaker. It was also wired with the hot and neutral reversed so that the metal case was sitting at 120 v - explained why I kept getting tingles when I touched the case. $20 for some input and output fuse holders and some internal rewiring fixed those problems.

I am currently eyeing a de soldering station because I am thinking about doing the wholesale re capacitorifacation thing on the NSX. I have a hot air rework; but, sometimes it can be a little clumsy and in tight quarters you can end up desoldering more stuff than you planned. Plus, if you get careless you can melt / light fire to things and burn your fingernails off. Aven is a US tool vendor and a little while ago they released a combination solder / de solder work station (the 17401). You can get it for about $270 at Digikey which is close to 2 times the Ebay price of the ZD985. Its a nice product because it also has a temperature controlled soldering iron and I figure its time to upgrade from my old fixed wattage Weller iron and hand held solder sucker. The Aven 17401 is manufactured in China; but, I expect that Aven being a US company it will have UL / CSA certification and like all things, there is good Chinese stuff and then the off-brand stuff. Aven's tools generally get good user reviews. Unfortunately, the 17401 is so new there do not appear to be any reviews on it yet.

The ZD985 looks like a good performing tool as long as it works when you get it. Just remember to unplug it rather than just shutting it off and then you don't have to worry about it burning the house down. As a tip, the off-brand Chinese vendors seem to sell the same product under different names and prices. Search around a bit and you may be able to find a product exactly like the ZD985 at a different price.

SWFL_NSX said:

Nice job! What type of desoldering station would you recommend? It looks like there is a wide range of price and features...

Click to expand...

Old Guy did a pretty good job recommending one. I've been using a Weller after hours at work and it's really nice, but not necessary.

I found it's easiest to get the caps out by first melting the pads and bending the leads straight with a small wooden dowel (screwdrivers work but damage the board). Then remove the cap by melting one pad and rocking the cap so that leg pulls up, then doing the same on the other side. Within 2 or 3 iterations it'll pop out. Since the leads were bent when they were installed any other method makes things more difficult. I'm only using the desoldering station to clear the holes once the part is out; I've tried using braid for that and it's a pain (plus it's messy).

SWFL_NSX said:

Could you keep track of the caps that are most likely to fail?

Again, love to see this sort of stuff. If the sound quality of this unit can be restored then if you combine it with a bluetooth adapter I don't see the reason to replace...

Click to expand...

I'm making notes of which ones are leaking as I remove them, but so far the list is below. The large value ones are really the worst off, so if I were to only replace a few I'd go after those.

SRS Unit:
2x 330 µF

Alpine:
2x 1000 µF on back connector PCB
2x 220 µF on bottom processor board
1x 1 µF on middle processor PCB
1x 1 µF on volume knob PCB
1x 4.7 µF on volume knob PCB

Quick update, today I finished removing the capacitors and verified that the spreadsheet is correct. Additionally, I verified that the height sensitive replacement caps would fit under the tape deck (they do). I feel confident that the spreadsheet in my original post is correct and can be relied on in case anyone else is as masochistic as I am

Old Guy said:

Lots of different de soldering stations. There are some pretty inexpensive off-brand Chinese vacuum style units that seem to be fairly effective. The EEVblog reviews a lot of electronics stuff and has this review on one popular off-brand station.

Click to expand...

Good stuff Old Guy. I'm waiting for crxguy52 to finish this project...if all goes well I'll probably pick up the Aven.

crxguy52 said:

Quick update, today I finished removing the capacitors and verified that the spreadsheet is correct. Additionally, I verified that the height sensitive replacement caps would fit under the tape deck (they do). I feel confident that the spreadsheet in my original post is correct and can be relied on in case anyone else is as masochistic as I am ​

Click to expand...

Thanks for the update...eager to see if this fixes the issues you've been having, or if more parts (op-amp?) need to be replaced.

Finally finished installing new caps! The plan is to conformal coat the board this weekend and re-install the following. The only snag I ran into was capacitor E601 on the bottom processor board - there was no polarity indicator on the PCB or old capacitor. Given that one lead is in series with another capacitor, it would seem that this is designed for AC signals, thus making a polarity irrelevant. The cap is rated to 50V so maybe the voltage rating is such that it can handle AC signals.

I'll post an update once I get it assembled and powered up.

It seems to be a BP (bi-polar). The instrument cluster also has two of them, 47 I believe. Not easy to get by.

Ah, that makes much more sense! It had BP written on the side, so I'm fairly confident you're right. I didn't know there was such a thing, luckily it looks like they're readily available on Digikey. I'll update the spreadsheet once I find a replacement cap.