1990 Bose radio / amps problem

[Don B.]

Hi - Only one of the four channels on our 1990 ZR-1 are working. I've queried an outfit called "corvetteradio.com" regarding this matter in an attempt to find out whether the amps or the radio are defective. I don't have a way to test the amps myself and hope that they will do this for me prior to any amp replacement. So here my question: Has anyone had any experience with this repair facility?? BTW, I have a feeling that the amps are bad in that the radio and the other amp work well together as expected. Apparently, these Bose systems has a bad reputation from what I've been told.
TNX, Don

[Joe L.]

Re: 1990 Bose radio / amps problem

Don-----

I'd say it's almost certainly the amps that are bad and not the radio head. NEW replacement amps are available that may cost about the same as repairing yours. I've seen these things advertised all over, but I don't recall where now.

[Don B.]

Re: 1990 Bose radio / amps problem

Thanks, Joe. I'll have to do a little more research to find the new replacements - I was assuming that repaired versions were all that's available.
Don

[William C.]

Re: 1990 Bose radio / amps problem

Don, if you do a web search you will find a number of outfits that offer repair of the amps, I had an shop in Texas do mine and was very pleased with both the price and the turnaround. Usually they fail in a mode that generates noise in the speaker, even with the volume turned down all the way, so if yours are absolutely dead, it might be worth sending in the radio head with the speakers as that type of problem is more likely to be in the radio itself if both rears are totally inop. BTW, there is also a link to a site that has pretty good instructions for removing the speakers, the rears are pretty easy, but the door speakers can be a bear. If you are working on the system, you might as well send the fronts out, but if you want to test them first, turn the volume at the radio all the way down and listen for noise at each speaker. A bad amp will still have a buzz in it under a condition with the radio volume turned down, as each speaker and amp are individually powered and the noise is internally generated.

[Joe C.]

Re: 1990 Bose radio / amps problem

Don:

You might try cleaning the 4 speaker/amp connectors at the back of the radio. I had a similar problem with the Bose unit in my '85 a number of years ago. I also, initially, blamed it on the amplifyers. 2 of 4 channels were very weak. I unplugged all 4 connectors and found what I believe are aluminum terminals, which had a very slight haze of oxidation. I cleaned them and problem was solved. It still works perfectly, approximately 10 years later.

Joe

[William C.]

Re: 1990 Bose radio / amps problem

Actually, the terminals are a tin coated brass material

[Larry S.]

Re: 1990 Bose radio / amps problem

You know this forum never stops to amaze me.
Who says its not keeping up with the times.I visit another on line Vette forum and if his question did not get answered I was going to suggest it to him.

Now I see we will be getting C4 restoration question answered here,But I have to tell you I will dread the day C5 restoration/Judging question are answered.Not because I dont like the C5,Only because it means the car and me will be old.

Good Luck on getting your car repaired

[Joe C.]

Re: 1990 Bose radio / amps problem

Bill:

Are you sure? Lots of 110 volt home electrical circuit breaker boxes use brass or copper connectors and circuit breaker burndy connectors with aluminum Romex (where code permits). The dissimilar metal contact causes galvanic action, resulting in faults, hot spots, and in some cases, fires.
The only reason that I offered aluminum as the material, was that, in the case of my '85, the oxidation looked like a fine, white powder. Possibly AlO2. I don't believe that a tinned connection will corrode in the same fashion.
In any case, whatever the connector material, the fellow should look for a bad connection before replacing the amplifiers.

Joe

[Don B.]

Re: 1990 Bose radio / amps problem

Hi Bill,
I"ve done a little more searching since I posted original. There are quite a few shops attending to this kind of service which implies that Bose amps don't last very long (poor engineering design by my standards). At this point, I doubt that the CDM is bad and that my problems are in the amps. I have 3 that do not work properly - 1 quiet, 1 oscillating with a constant tone level, and 1 that has static-like noise. The other amp seems to work fine - a good sign that the CDM is probably okay from what I've read. Thanks to information on two of the websites visited, I find that I can trouble shoot this problem easily by making up a wiring harness (4 wires) and use it to rotate thru the channels using the working amp/speaker assy. An alternative is to remove the working amp/speaker assy and connect it to each of the other positions - a good idea if one doesn't have an electronic background. I do have the background so I'll make the harness and clip-lead into connectors. Thanks for the input. Don

[William C.]

Re: 1990 Bose radio / amps problem

Yes, I worked in design and quality control at the manufacturer for about 37 years, from about 1980 on, everything was tin-plated over a non ferrous base, "Brass" is a vauge description covering a bunch of formulations, including some for high temp and some for high conductivity.

[Don B.]

Re: 1990 Bose radio / amps problem

Hi Joe,
That's an excellent idea and I'll check the connectors. When I looked at the connector on the channel (LR) that I removed yesterday, I did note that the connector pins were plated with a cheap material if plated at all. It wouldn't take much oxidation to screw up the audio portion. This potential answer to my problem is even more important since the car originally came from the east coast and a humid environment - a real oxidation generator. The only channel amp that may need replacing is the one that oscillates. Thanks for the suggestion. Don

[Don B.]

Re: 1990 Bose radio / amps problem

Geez, you'd think for the price of a ZR-1 that they'd use a better quality plating than tin which can easily oxidize.

[Don B.]

Re: 1990 Bose radio / amps problem

I'm just glad there are people on-line who are willing to share experiences and offer good suggestions. This site contains a wealth of information - where else can you find this kind of resource for free? - and I hope I can help as much as I've been helped. Don

[Clem Z.]

Re: 1990 Bose radio / amps problem

i am not a audiophile(?) but don't they use gold plating on these type of connector now to prevent oxidation?????

[William C.]

Re: 1990 Bose radio / amps problem

Occasionally in high end audio, but the only gold in typical automotive applicatons was in SIR (Air Bag) systems.