EU Radio Head Unit (EUDM 1991) - Repair

Joined
5 August 2014
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229
Location
Germany
Another radio with intermittent sound output arrived at my desk. It was previously repaired in 2008 but not exactly in top quality.

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state of repairs 2008

Nevertheless it played fine for 5-20 minutes when it suddenly dropped silent. Different from a previous case regarding a USDM radio the main flex cable connectors where still looking good, so it had to be something different.

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trouble shooting and tracing

As soon as the audio went out, the voltage at the two main output amplifiers was checked and suspiciously low (3.9 V, should be ~10 V). This 10 V supply is generated by the Zener diode ZD807 but measured fine at the diode. As always in such cases, it's best to work backwards. After a bit of tracking and tracing, it became obvious that the 10 supply was fine but somehow did not reach the amplifiers that depend on it.

The reason was quite simple: A broken trace caused a disconnection on the way. After confirming it on an old board and adding a repair wire, the sound came back and was working stable again.

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an additional (yellow) repair wire

Besides the repair, the power supply PCB had its leaking capacitors exchanged, the volume knob fastened and a flex cable replaced that didn't look very good any more:

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leaking capacitors on the power PCB

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a fixed knob

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a damaged flex cable


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a cleaned PCB with tracks covered in solder


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.. backside

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final result with all parts re-installed

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final checks

BTW, the really interesting part was that the radio had been to a professional repair shop before and couldn't be fixed. They stated:

"The unit was carefully disassembled and and each part checked according to schematics. It needs to be retuned in an unrepaired state. The audio processor was checked and considered defective. After a long search we found out that it's no longer available."

This raises a lot of questions since the NSX radio doesn't have an audio processor and schematics haven't surfaced anywhere yet. In addition, everything that could be considered a processor in this radio is Alpine proprietary and was never freely available. My guess is, they opened it, couldn't find the issue and simply returned it charging their standard fee ..

PS: Circuit information regarding the 10 V supply has been added to the Radio Repair III page.
 
Another radio with intermittent sound output arrived at my desk. It was previously repaired in 2008 but not exactly in top quality.

Click image for larger version. Name:    PXL_20240107_183852196s.jpg Views:    0 Size:    120.6 KB ID:    14896
state of repairs 2008

Nevertheless it played fine for 5-20 minutes when it suddenly dropped silent. Different from a previous case regarding a USDM radio the main flex cable connectors where still looking good, so it had to be something different.

Click image for larger version. Name:    PXL_20240106_180125647s.jpg Views:    0 Size:    91.2 KB ID:    14893
trouble shooting and tracing

As soon as the audio went out, the voltage at the two main output amplifiers was checked and suspiciously low (3.9 V, should be ~10 V). This 10 V supply is generated by the Zener diode ZD807 but measured fine at the diode. As always in such cases, it's best to work backwards. After a bit of tracking and tracing, it became obvious that the 10 supply was fine but somehow did not reach the amplifiers that depend on it.

The reason was quite simple: A broken trace caused a disconnection on the way. After confirming it on an old board and adding a repair wire, the sound came back and was working stable again.

Click image for larger version. Name:    PXL_20240106_185608078s.jpg Views:    0 Size:    137.8 KB ID:    14894
an additional (yellow) repair wire

Besides the repair, the power supply PCB had its leaking capacitors exchanged, the volume knob fastened and a flex cable replaced that didn't look very good any more:

Click image for larger version. Name:    PXL_20240107_182422748s.jpg Views:    0 Size:    91.9 KB ID:    14895
leaking capacitors on the power PCB

Click image for larger version. Name:    PXL_20240107_183530256s.jpg Views:    0 Size:    77.0 KB ID:    14897
a fixed knob

Click image for larger version. Name:    PXL_20240107_183800961s.jpg Views:    0 Size:    58.1 KB ID:    14898
a damaged flex cable


Click image for larger version. Name:    PXL_20240114_161442997s.jpg Views:    0 Size:    62.8 KB ID:    14899
a cleaned PCB with tracks covered in solder


Click image for larger version. Name:    PXL_20240114_161450790s.jpg Views:    0 Size:    66.1 KB ID:    14900
.. backside

Click image for larger version. Name:    PXL_20240114_163025394s.jpg Views:    0 Size:    92.0 KB ID:    14901
final result with all parts re-installed

Click image for larger version. Name:    PXL_20240114_170434362s.jpg Views:    0 Size:    93.6 KB ID:    14902
final checks

BTW, the really interesting part was that the radio had been to a professional repair shop before and couldn't be fixed. They stated:

"The unit was carefully disassembled and and each part checked according to schematics. It needs to be retuned in an unrepaired state. The audio processor was checked and considered defective. After a long search we found out that it's no longer available."

This raises a lot of questions since the NSX radio doesn't have an audio processor and schematics haven't surfaced anywhere yet. In addition, everything that could be considered a processor in this radio is Alpine proprietary and was never freely available. My guess is, they opened it, couldn't find the issue and simply returned it charging their standard fee ..

PS: Circuit information regarding the 10 V supply has been added to the Radio Repair III page.
Well done Lars. Now......if only mine was that simple!!!
 
What is the cost to do a radio repair ballpark?
 
Usually around a few hundred Euro but the chances of success are roughly 50/50 (due to age and damage from capacitor leakage) and considering the costs for shipping/tax to and from the USA it's often uneconomical from outside the EU, to be truely honest ..
 
Last edited:
Hi bsansx,
Usually around 400 Euro but the chances of success are roughly 50/50 (due to age and damage from capacitor leakage) and considering the costs for shipping/tax to and from the USA it's not really recommend, to be truely honest ..
Regards
Lars
Lars
thank you for your honest answer. I am trying to find someone in the states now.
 
Usually around a few hundred Euro but the chances of success are roughly 50/50 (due to age and damage from capacitor leakage) and considering the costs for shipping/tax to and from the USA it's often uneconomical from outside the EU, to be truely honest ..
Lars
does anyone sell all the common parts needed to fix a 1993 radio?
 
any update on finding a radio repair shop stateside? mine has been down for some time and want to keep it OEM
I am calling everyone i can. There was a guy in cali but he said the last 5 were beyond repair. He did say i can send it in if i want to see. I need to pull mine out and look at the boards to see if its damaged from the leaking caps. Have you looked at you unit yet? I will keep everyone updated if i find someone.
 
I repaired mine using the parts list posted in another thread and some basic soldering tools.

The work of removing capacitors and repairing disrupted traces is fairly straightforward and requires no knowledge of electrical components. I think I spent $500 in total on a Weller soldering iron and de-soldering iron.

We're very luck to have Heineken in the community because he is doing deeper level diagnostic work, which is a different story. But some radios will come back to life with basic component replacement.

Why not give it a shot?
 
I have talked with United radio service in Syracuse NY. Two months ago they said send it in and yesterday i finally pulled it out and called they to make sure where to send it. Long story short they were not going to take it but i spoke with the repair guy and he said send it in. He said some parts are gone like belts to the tape deck and they cant get them but if its the caps they will try. I am sending it to them this week and will let you know what happens. I opened it up and the board did show signs of leakage but not too bad.
 
I have talked with United radio service in Syracuse NY. Two months ago they said send it in and yesterday i finally pulled it out and called they to make sure where to send it. Long story short they were not going to take it but i spoke with the repair guy and he said send it in. He said some parts are gone like belts to the tape deck and they cant get them but if its the caps they will try. I am sending it to them this week and will let you know what happens. I opened it up and the board did show signs of leakage but not too bad.
I Have the radio at United radio service does anyone have a common parts list that fails? They purged all their records.
 
I repaired mine using the parts list posted in another thread and some basic soldering tools.

The work of removing capacitors and repairing disrupted traces is fairly straightforward and requires no knowledge of electrical components. I think I spent $500 in total on a Weller soldering iron and de-soldering iron.

We're very luck to have Heineken in the community because he is doing deeper level diagnostic work, which is a different story. But some radios will come back to life with basic component replacement.

Why not give it a shot?
Do you have a copy of the parts list?
 
I Have the radio at United radio service does anyone have a common parts list that fails? They purged all their records.
Like stated a few messages above, there is no such list.

There are too many capacitors to replace them all. Let them replace all caps with vent marks on top and don't forget the power PCB on the back. If they are a reputable shop they should be able to identify replacements.

If the rado fails to work after replacing the caps, and cleaning/repairing the PCB, further trouble shooting is necessary. Flex cables and their connectors could be contaminated and might need replacement as well.
 
I received a note from United radio service that they could not fix my radio due to all their records on the radio were purged from their system. He said he didn't think they could do a reliable repair without them. When i get it back i will check to see what was done if anything. I have a email into them to see if anything was done at all. I will look at trying to do it myself or I might just try to see what the cost is to ship it to Heineken for the repair. I wish i had a better answer for us in the NSX community.
 
Today i am giving my radio to a local guy who says he might be able to fix the radio. I will keep you all updated. If this doesn't work i will send it to Heineken.
 
Quick update on my radio. Caps were changed out but there is a transistor that is damaged and he is trying to source it. Seems like Heineken has one in his shop with the same issue.
 
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