DIY: OEM Alpine Head Unit Capacitor Replacement

[goldNSX]

It had BP written on the side, so I'm fairly confident you're right. I didn't know there was such a thing...

I'm more than confident that I AM right. BP are not very widespread these days and usually seen in older audio equipment. So not uncommon to see one in the alpine headunit. I was a little bit surprised to see them in the instrument cluster (brake lamp circuit) and had some problems getting these (I guess Würth was the only brand available). Happy soldering!

 

[ThumperAC]

watching this thread closely, would love to get my OEM unit working again

 

[SWFL_NSX]

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

Any update [MENTION=18814]crxguy52[/MENTION]?

 

[crxguy52]

I had some things come up over the past few weeks but I got around to conformal coating the boards this past weekend. If it wasn't so cold out I'd have done it outside - that stuff is strong! Putting it back together this week and hopefully testing it out over the weekend. I used Acrylic conformal coat to match what was on the boards.

I should mention (and I'll update the spreadsheet to reflect this) that E601, the bi-polar cap needs to be laid down sideways in order to clear the tuner knob PCB. The original cap was a lot shorter. Otherwise everything fits mechanically.

 

[JLCoolman]

Awesome thread!

Hope it all works out well for you. Looking forward to hearing of your positive results.

I have two headunits (my original and a used one that I replaced it with) that are probably/hopefully on the early side of starting to experience issues, but more than likely I'll try to see if Willman's Electronics is still willing to attempt repairs.
Ah, I forgot about Hi-Tech Electronic Services as well, posted about in the following thread:
http://www.nsxprime.com/forum/showt...know-a-thing?p=1960307&viewfull=1#post1960307

Can you give an estimate of about how much all the replacement caps cost? And maybe the cost of just the leaking/major ones that need to be replaced?

 

[Old Guy]

Can you give an estimate of about how much all the replacement caps cost? And maybe the cost of just the leaking/major ones that need to be replaced?

I will let crxguy52 give you the specifics; but, I speculate that if you use Digikey as the supplier the cost of all the capacitors will probably be less than the cost of Digikey's flat rate for small package shipping ($8 in Canada). You should buy two complete sets of capacitors to fix both head units - that way you drive down the effective price per capacitor even lower :smile:.

 

[crxguy52]

Awesome thread!

Hope it all works out well for you. Looking forward to hearing of your positive results.

I have two headunits (my original and a used one that I replaced it with) that are probably/hopefully on the early side of starting to experience issues, but more than likely I'll try to see if Willman's Electronics is still willing to attempt repairs.
Ah, I forgot about Hi-Tech Electronic Services as well, posted about in the following thread:
http://www.nsxprime.com/forum/showt...know-a-thing?p=1960307&viewfull=1#post1960307

Can you give an estimate of about how much all the replacement caps cost? And maybe the cost of just the leaking/major ones that need to be replaced?

Thanks! According to the digikey cart in my first post, the total comes to ~$29 before shipping. This includes a few extras of each cap in case something happens. Total time for replacing all the caps\coating was probably >20 hours (not including removal\install of the radio), but I took my time and double checked each value against the spreadsheet to make sure I was doing it right. With some work instructions it could have probably gone a lot faster.

If you wanted to just replace the big and\or leaking ones, it could probably be done in under 5 hours. Off the top of my head there were ~8 large caps (one was leaking) and several smaller ones that were leaking. Total cost would be well under $10.

 

[crxguy52]

Plugged it in last night and... success! I only had time to test test the radio and buttons on the front face (left my aux cable elsewhere), but everything appears to be working as it did before, sans "warmup" period.

The only drawback I found was a very low baseline level of white noise when the unit was on - only loud enough to hear while the engine was off and sitting in a quiet garage. It was not volume dependent, meaning it's being introduced somewhere in the output stage (not pre-amplification). It very well may have been there before and I just didn't notice it. Not a big deal, just an observation.

I also managed to loose a few screws that hold the case together. For other's reference, they appear to be M2.5x0.45 (6mm long) cheese head screws. I've ordered some from McMaster (94017A152), I'll update if this info isn't correct.

 

[goldNSX]

a very low baseline level of white noise

The BOSE speakers also that.

 

[MotorMouth93]

Nice work! You should be set for another 30 years or so!

One thing I'm curious about is how much the head unit itself degrades the signal. We know that the factory stereo system isn't great, but could it be great if you removed the Bose speaker/amplifiers and replaced them with aftermarket speakers and amp? It seems to me like you could fit 6.5" component speakers in the doors (or coaxial if you don't want to add holes for tweeters), a small sub (8" maybe?) in the footwell, then use a 4 channel amp with 2 channels bridged for the sub and the other two channels for the door speakers. You'd lose the rear center channel but that speaker doesn't do much anyways. I might have to do some experimenting before I put my interior back together.

 

[SWFL_NSX]

Plugged it in last night and... success!

Awesome! I'm going to order the parts and give this a shot.

 

[crxguy52]

I might have to do some experimenting before I put my interior back together.

Definitely post your results. While I'm glad I fixed my head unit, there are certainly faster\easier options out there.

Awesome! I'm going to order the parts and give this a shot.

Let me know how it goes, I'd be interested to see what the insides of yours look like.

 

[warrenw]

Excellent!
the white noise was there before. Mine has always had it.

Great thread, another example how NSX Gen1 owners are, in reality, NSX Gen1 caretakers.

 

[MotorMouth93]

Definitely post your results. While I'm glad I fixed my head unit, there are certainly faster\easier options out there.

Oh no I'm not talking about replacing the head unit, I'm talking about using the factory head unit with aftermarket speakers/amplifiers to keep the OEM look and functionality but have better audio quality. I suspect the Bose speakers are the weak link rather than the head unit.

 

[crxguy52]

Excellent!
the white noise was there before. Mine has always had it.

Great thread, another example how NSX Gen1 owners are, in reality, NSX Gen1 caretakers.

Thanks! Most people cringe when I tell them I rebuilt my head unit, but I think it's fun. My S2000 was boring because there was never anything to fix. I think there's something wrong with me.

Oh no I'm not talking about replacing the head unit, I'm talking about using the factory head unit with aftermarket speakers/amplifiers to keep the OEM look and functionality but have better audio quality. I suspect the Bose speakers are the weak link rather than the head unit.

That's an interesting idea, since the amp and speaker are all hidden away. I think Kaz mentioned in one of his posts that there are a bunch of small aftermarket amps on the market now which could open the door to using aftermarket speakers. The challenge would be building an enclosure, but I don't see why you couldn't 3d print one and lay some fiberglass on top for strength. Quick and easy.

 

[Old Guy]

The Bose amplifiers are class D amplifiers as are just about all the OEM and aftermarket audio amplifiers these days. The primary evolution since the days of the Bose, as far as I can tell, is that the switching frequencies have moved from the 140 kHz used in the Bose to up in the MHz range. I think the advantage of the higher switching frequencies has nothing to do with fidelity and more to do with the ability to save $ because it reduces the output filtering requirements (those big clunky inductors on the Bose amps). They also now have H bridge modules on a single die eliminating the requirement for 4 separate FETs which reduces packaging (and cost). As such, I am not sure that amplifier replacement is necessarily going to result in an improvement. The Bose amplifiers do have feedback from the output into the modulation stage and they have some up front signal shaping, so replacing the amps with a non tailored amp will likely result in an audible change. The change may or may not be to your liking. That signal shaping stuff was how Bose customized the same amplifier module for the doors and subwoofer in the NSX, ZR1, some Cadillacs and probably some other vehicles.

Changing the speaker may or may not net an improvement, depending on what improvement you think it needs. As crxguy52 alludes to, retaining the original ported enclosure may be the bigger issue and most of the benefit might come from a larger enclosure; but, I am thinking you might be pretty constrained there if you want to continue to be able to roll your windows down all the way.

I think the biggest impediment to good sound quality is probably the NSX itself. It is not exactly a concert hall environment, particularly when you are on the highway with the roof panel off.

 

[SWFL_NSX]

I just reinstalled my radio after removing, disassembling, de-soldering and replacing a bunch of caps. I'm happy to say that it is working much better, but not yet at 100%. Here is some documentation for others that want to attempt the repair; this unit will be pulled again for further troubleshooting when I take apart the dash to R&R a leaky evap.

Original Symptoms: Unit would take a very long time to produce sound after the car started Many times the sound would never come on. Audio had scratches, hisses and pops when it was on (really just un-listenable).

Outcome: Original symptoms cured, still have a very light hiss (seems to be from center channel only, so I suspect the center speaker between the seats) and my volume control is no longer working (believe this is from a poorly seated ribbon cable on reinstall)

Radio Version:
P/N39100-SL0-A000-M1
Ref No: CM3939
Serial No: B10613713AB
From a 1992 NSX

Tools/Materials used:

Vacuum Desoldering Station ZD985 that was reviewed in the video above
Weller Soldering iron WES51
Solder, desoldering braid, conformal coating
Isopropyl Alcohol and tool to apply
Dental pick or small screwdriver
All caps ordered from CRXguy's list in the first post (this was correct for all but one of the caps in my unit)

Step 1-Read through all of Kaz's blog (link in the original post by CRXGuy). Kaz has repaired a dozen or more of these units, and you will begin to notice a pattern of failure for the caps that needed to be replaced. I only replaced the caps that showed signs of failure (the three large ones on the bottom processor board) or the ones that Kaz recommended as preventative (the two on the power board; these turned out to be leaking as well, but showed no outward-symptoms).

Step 2-Remove radio, disassemble. Be gentle while separating the boards; if you are forcing something, you are probably breaking it. Some of the screws will be soldered in; I used extra heat from both tools to get the solder to melt. Use special caution around the FFC ribbon cables (more on this in a bit).

Step 3-Examine the board for any evidence of cap failure-if you've looked at all of Kaz's pictures you should be familiar with what it looks like-discoloration on the traces, dark fluid (acid) leaking on the board itself, or bulging caps. Remove the caps with the de-soldering station and replace with the new ones (check the values along the way, especially if your radio is a different model). If the FFC ribbon cables show evidence of corrosion scrape it off as best as possible. If the corrosion has gotten to the traces on the board, scrape off the corrosion, clean the area with the alcohol, and re-apply conformal coating. If the corrosion has eaten away the trace, rebuild the trace with flywire, clean with alcohol and the apply the conformal coating. Spray contact cleaner on the volume potentiometer.

Step 3-Reassembly is straightforward except for the FFC ribbon cables. They were very difficult for me to get correctly seated and I think that the new issue with my volume is because of a partially seated ribbon cable. The FFC cables are available but I couldn't find an exact replacement. Ours seem to be 1.25 pitch with varying lengths, number of pins, and orientations.

Wrap up- To echo Kaz, I'm not an audiophile, but to my ears the stock radio sounds pretty good, and looks fantastic in the dash. I'm happy with this repair, even though I introduced a new symptom (no volume control), and will investigate this issue as time allows. Pictures of the failure points on my radio below:

Three large caps on the lower processor board-this seems to be a pretty constant failure point. There was no potting on mine, this pic shows the repair after the acid had been scraped off the traces, but before the conformal had been applied. I also coated the traces with solder, but I don't think this is necessary.



Example of the FFC cable. This one was 1.25 pitch and 14 pin, but I couldn't find a replacement with the conductors on the right side. I scraped off the corrosion as best I could and re-inserted it. Finding an exact replacement for these cables would be great-even better if we could find ones that are a bit longer to make reassembly a little easier.



Here is one of the two caps replaced on the power board. In one of his blog posts Kaz recommended doing this-when I took mine off it was obvious they were leaking.



Hope this helps somebody!

 

[crxguy52]

I just reinstalled my radio after removing, disassembling, de-soldering and replacing a bunch of caps. I'm happy to say that it is working much better, but not yet at 100%. Here is some documentation for others that want to attempt the repair; this unit will be pulled again for further troubleshooting when I take apart the dash to R&R a leaky evap.

Glad things went well and the spreadsheet was helpful! When you pull it back apart I'd recommend replacing the caps on the volume control PCB - I think both of mine were leaking. I also found one on the middle processor board in the back, it's all noted in the spreadsheet.

Do you think the ribbon cable is shot and causing the volume not to work? If so, did you consider replacing the connector on the board and going with a different style cable? I would imagine the connector has a standard footprint and wouldn't be too hard to find. Related to the ribbon cables: I found it was easiest to install all of them on the bottom board first, then feed the cables up through the head unit and plug it into the individual boards once the bottom one is installed. Otherwise it's a real pain.

I ended up ordering a few more tools that were helpful, in case others want to attempt this:
Fiberglass sanding pen - very useful for removing damaged conformal coating. Way easier than using
Acrylic conformal coating - this is what's on the boards to begin with and is alcohol soluable.

 

[warrenw]

I have been putting this off, been really busy and didn’t put any time aside this winter to pull the head unit.
This spring, I started up the car for the first time and the head unit is dead, does not power up, no noise, nothing. Only buttons light up when headlamps on.
Really? It dies when not being used. I know there is power to the unit for presets through the clock fuse, but the sig lighter works, so it isn’t the #8 fuse.
It was working 100% in November.


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[metsuki]

i had an issue with my radio.
i did not use it since a year because the right speakers seems dead, and i think the bose amp was dead.


when i put back my CCU in the car i check for the radio in the mean time and there was no sound at all from it. not from any speakers. so i think it was a radio issue and not a bose amp issue.
i saw your thread and many from Kaz and tried it myself


i put the radio out and obviously there was some caps leaking (mostly the 2200um and the 1000um)


i did the same i did with the CCU, changing the 2200's, 1000's, and 470's from the amp plate and power plate. i had to make a little bridge where a track was gone. i did my best even if i am not please whith it
the tracks was not so corroded as you can see on the picts.

i put everything back together.
now when i put on the radio, all the speakers play!!!! but not very right
the gain seems to be all messed up on each input. radio is scrachy and full of bass, cassette seems overdriven like to much gain too, and the CD charger is very low volume but if i cranck the volume really high the sound is quite good .


i think i have a problem with the op amp 4560? what do you think? it is the only component in the acid path and i saw kaz change them from time to time
where else do i have to search?

thank you for your help

 

[crxguy52]

[/QUOTE]

FYI Your pictures aren't showing up - I had to upload them to prime. Glad to hear that you had some success repairing your head unit. Honestly as far as the op-amp is concerned you know more about it than I do at this point - I just focused on replacing the caps. Definitely reply back with results!

I have been putting this off, been really busy and didn’t put any time aside this winter to pull the head unit.
This spring, I started up the car for the first time and the head unit is dead, does not power up, no noise, nothing. Only buttons light up when headlamps on.
Really? It dies when not being used. I know there is power to the unit for presets through the clock fuse, but the sig lighter works, so it isn’t the #8 fuse.
It was working 100% in November.

Sorry to hear that! If the fuse isn't blowing, it sounds like one of the traces got eaten through - maybe start with the power\connector board?

i had an issue with my radio.
i did not use it since a year because the right speakers seems dead, and i think the bose amp was dead.


when i put back my CCU in the car i check for the radio in the mean time and there was no sound at all from it. not from any speakers. so i think it was a radio issue and not a bose amp issue.
i saw your thread and many from Kaz and tried it myself


i put the radio out and obviously there was some caps leaking (mostly the 2200um and the 1000um)


i did the same i did with the CCU, changing the 2200's, 1000's, and 470's from the amp plate and power plate. i had to make a little bridge where a track was gone. i did my best even if i am not please whith it
the tracks was not so corroded as you can see on the picts.


i put everything back together.
now when i put on the radio, all the speakers play!!!! but not very right
the gain seems to be all messed up on each input. radio is scrachy and full of bass, cassette seems overdriven like to much gain too, and the CD charger is very low volume but if i cranck the volume really high the sound is quite good .


i think i have a problem with the op amp 4560? what do you think? it is the only component in the acid path and i saw kaz change them from time to time
where else do i have to search?

thank you for your help

FYI Your pictures aren't showing up - I had to upload them to prime. Glad to hear that you had some success repairing your head unit. Honestly as far as the op-amp is concerned you know more about it than I do at this point - I just focused on replacing the caps. Definitely reply back with results!

 

[Old Guy]

Just a little tip if you have a surface trace that has been completely or severely damaged by capacitor electrolyte. Rather than try and create a solder bridge between the broken traces, you remove some of the protective varnish from the trace at a convenient distance back from each side of the break (I think Mode makes a nifty little pen that is collection of glass fibers - good for carefully scraping off the top coat). Then you take a piece of 30 awg wire wrap wire and solder it to the bare spots on either side of the broken trace creating a bridge. Normally, you can make the wire wrap bridge as long as you want. You can buy a small reel of wire wrap for about $15 or so from DigiKey. They also sell something like 10 or 20 4" precut lengths that are pre stripped for much less. The pre stripped is nice because a 30 awg stripper is not a tool that most people have. The Klein or Greenlee strippers that you use on your house wiring are definitely a no-go. A single sided razor can be used to gently scrape the insulation off in a pinch.

Of course, this only works if the trace is accessible.

 

[warrenw]

I didn’t find any 470uF leaking. Anyone else?


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[warrenw]

Q704 on the middle board towards the back of the unit. Top of picture.
Mine is blown!
How can I determine what it is?

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[Old Guy]

That is unfortunate. Based upon the other transistors on the board, I am going to speculate that the tiny SMD packaging hasn't exactly left a lot of room for any useful identifying marks?

My first reaction would be to try and contact the Williams guys who do the retrofit on the NSX head units and see if they have any reclaimed 'guts' from a head unit that they would be willing to sell to you, or at least the board with the failed transistor. If that does not pan out, all is not totally lost; but, does require some potential experimentation.

Its been a number of years since I had my head unit apart to clean some crap off of the inside of the display, so I don't recognize the boards. However, I am guessing that this might be the control board rather than an analog signal path board? If so, that might be a good thing because the transistors tend to operate in the saturated mode rather than in their linear range. This means that the characteristics of the transistor are less critical as long as you respect the maximum operating voltages and currents, so you have the option of over specing the transistor. The biggest issue will be figuring out whether it is an npn or pnp bipolar transistor or an N or P channel FET of some ilk.

Update - I went back and looked at the pictures in the first post. crxguy52 refers to the board as the top control board, so likely the failed transistor is not in the analog signal path. Chances are the transistor is operated in the off state or fully saturated on state. That likely means that the transistor parameters are less critical giving you a lot more flexibility in selecting a replacement.

Based upon your description of the failure, I am going to guess that this transistor is involved in the power up process for the head unit. I say this because it looks like the transistor is a SOT23 package which makes the single pin side the transistor the collector and the lower right pin the emitter which are the heavy current carrying terminals on the transistor. These look like they are connected to the heavy traces on the board. The lower left terminal on the SOT bipolar transistor package is the base / low current control signal which is connected to the small trace. This could also be a FET because the SOT23 package for the FET has the similar pin alignment for the source and drain (heavy current) and gate (control signal). The first trick will be to determine whether the package is an NPN versus PNP or N versus P channel FET. You could try to figure out the device polarity by tracing the circuits; but, the easier way might be to carefully remove the transistor and then power up the head unit on the bench and then see if you can measure any voltages on the collector and emitter trace connections relative to ground. If there are potentials present, then this would give you an excellent clue as to the polarity of the transistor. As to whether it is a bipolar transistor or a FET, I would guess bi polar; but, you would have to do a complete circuit trace to be sure. Once you determine whether it is an NPN or PNP, all you have to do is go to Digikey and pick from what could be a couple of thousand likely candidates (which may be easy if you are OK with over specing the transistor).

Before you engage in the transistor experiment, have a look at other components on the board. Particularly for something connected to those heavy traces that might have shorted out. Although transistors do fail due to internal problems, it is pretty rare. Transistors failing like that are typically caused by significant overload. No point in trying a transistor replacement until you have addressed the underlying cause.

If you are feeling particularly ballsy / nothing to lose, I suggest the following experiment. Get some of those AGC glass fast blow fuses. A 1/8 - 1/4 amp rating would be good starting point (may need to find an electronics supplier to find something that small). Attach some jumpers to the fuse. With the failed transistor removed from the circuit, place the jumpered fuse between the emitter and collector traces on the circuit board and power up the head unit on the bench to see if the unit responds to the power switch and other functions. If there is no response or the fuse blows, that might be an indication that there is some other problem which precipitated the transistor failure and that problem is still there. AGC fuses are fairly quick blow so the chances of doing additional damage is small if there is a problem. This is all a bit of hit and miss in the absence of wiring diagrams and component values.

I still think the call Williams route might have the best chance for quick success.