Need help with Bose Cassette Deck - Not normal issue
 

All,

I've been working on my 86 convertible project and, of course, the Bose system had issues when I bought it. I've managed to find a good amount of information on rebuilding the speakers and have successfully reconditioned almost two complete sets (I bought a whole other Bose system from an 87 coupe on eBay for $60! Four complete enclosures and head unit to practice on before I worked on my equipment).

So after I finished the speakers, I decided to turn my attention to the head unit. The unit that came in my car has the typical issue of flipping the tape twice and ejecting it. When I tested the eBay unit, miraculously, the cassette deck worked! This was great news since no one repairs these anymore.

Well, with the aid of the factory service manuals for the head unit and the speakers (graciously donated to me by a forum member who no longer had his 86), I set about rebuilding the head unit myself. In looking at antique radio sites, many contained the same advice for old radios as is posted regarding the Bose speaker amps; replace the electrolytic capacitors. I disassembled the head unit, cleaning all the controls with cleaner/lubricant, cataloging and ordering replacement capacitors from Digi-Key and got to work with my soldering iron, de-solder braid and some high quality solder. OK, let me just say from the experience that there is a reason the vendors get a lot of money to do this work. It is very labor intensive, and if they are doing what I do, then they are providing good value as the job is a little more complex and time consuming than I thought.

I also rebuilt the cassette deck of the unit since it worked. I cleaned the entire mechanism, reconditioned the pinch rollers, cleaned and de-magnetized the tape head and replaced the belts (which are available at kens electronics).

Tonight I re-assembled the unit and put it in my car to test. The FM radio portion worked perfectly and the sound quality is very good. There is a noticeable difference in the unit's sound, and then I tested the cassette deck....

The deck will still play and sounds great. All functions work including the search features, and with the cleaned heads and rollers, tapes sound very nice.

The problem is that the tape won't stay in the deck. Whatever mechanism is meant to hold it seems to not be grabbing, so I have to hold the tape in the deck to get it to continue playing.

There is a solenoid that gets energized to retain the tape in the deck and it doesn't seem like this is happening anymore. I'm so close to having a fully functional head unit I can taste it.

I know this a deep question and there are only a few folks who might have gotten this far into the unit, but can anyone offer any tips for what I should look for?

This assembly was a test to see if the re-capping worked. I still have to disassemble the head unit so I can add the iPod input so I have to get back in there anyways but wanted to check the forum knowledge.

I am taking pictures and do plan on documenting the work I am doing and sharing a write up for the forum. This information is scattered around the web and we need to get it consolidated before it is truly lost.

Thanks in advance.

Getting the cassette to work in these radios is very difficult. I've had very little success in doing it.

No surprise for 30+ year old radios to have some troubles. The radios and receivers were not intended for dealer service. The repair information went to authorized service centers. You could try AC Delco repair centers for tips and parts souces. You might get lucky and get a tech not a order taker.

I should mention that the tape retention mechanism was working when I originally tested the unit, so obviously I did SOMETHING in working on it. I'm gonna have to tear it down again.

I needed a complete unit for my 85....found a guy on e bay from British Columbia, no less, that rebuilds and sells our radios....the cassette is new and works perfectly so I think he knows what he's doing. search for 86 covette bose radios...should turn him up....

Solved!
 

OK, I just got back from vacation and tore back into the radio to install the iPod adapter port and look at the cassette.

iPod adapter install went beautifully, and the sound from the refurbed radio and Bose speakers is really impressive, I have to say I am very pleasantly surprised and for a factory system in 1986 this system was top notch.

In tearing down the cassette unit, I immediately went to the solenoid which holds the tape mechanism. I confirmed that the coil did not have any continuity, so I removed it to examine it and sure enough, the tiny wired from the coil had come undone from the connector posts. Unfortunately, I was not able to reconnect these as one was too short to make the connection and eventually broke right at the coil when I moved it one too many times.

After this mishap, I opened my second unit and pulled the cassette deck from it. I was sort of relieved to find that this deck was unrepairable due to the capstans being damaged beyond any repair. So I scavenged the solenoid from this unit (which tested OK) and put it in my refurbed unit.

After re-assembly, SUCCESS! And with good audio quality.

I now have a refurbed unit with a fully functional cassette deck, iPod adapter which goes right into the equalization board (so tone controls work), and I even replaced the radio lighting with LED bulbs so it is nice and bright at night.

This project was very labor intensive and of intermediate difficulty, so I can see why the vendors get a good amount for it, and consequently, why folks just rip out the systems. But I like to have the period stuff working in the car, it adds to the charm. I love watching the look on people's faces when I put an 8-track in my 78.

I will be putting some documentation together for this project and posting when I get some time to get it written up.

SLVRSHRK do you have a link to or are you willing to show how you added the ipod input to the system? I have looked a few times only to find services

I am working now to do the write-up but want to make it complete so it is taking more time due to the number of diagrams I am having to create. I got most of my information from the schematics in the factory service manual for the radio (not the car FSM). It has all of the information, but I don't want to risk any copyright issues so I can't/won't use any of the actual diagrams from the manual. This means I am having to create custom diagrams in Visio and put them into the doc.

Probably need two weeks or so to finish the document as it will include not just the iPod adapter info, but also the info on refurbishing the speaker amps, radio unit and some items for the cassette deck if you are so inclined.

I would consider this mod a somewhat intermediate skill level project, and definitely upper level if you are going to tear into the guts of the radio and cassette unit. Definitely need some experience and practice in de-soldering and soldering components to get the job done. If you are comfortable with these techniques, it's just time.

I am excited to see your write up. I throughly enjoy working on electronics and being able to refurb the original bose system would be fantastic

Looking forward to your write up, especially the cassette

Greetings! I have a 93 bose system with rear speakers not working very well. Have the units out and would to know what each incoming wire to the amplifier is for, Black must be ground but I would to know which wires power the amp and which are signal to the amp. Would like to check the signal from the head before taking the amps apart. Regards, Rob

Bob,

They changed the system a bit in 90 I think so I don't have any specific information for that year. Have you looked in the Factory Service Manual? If you don't have one of these yet for your year, I would definitely recommend picking one up as they are really useful for working on the car.

Short of all that, it will be a bit of trial and error.

If both speakers have different issues, you might try just swapping them (plugging left speaker into right connector and vice versa) to see if the issue travels with the speaker itself. If it does, the issue is most likely within the speaker. If not, it could be in the signal from the head unit.

Best of Luck

Greetings! Hey sorry for the late reply.
had severe difficulty with the thread downloading. I do have the shop manual, well thumbed, I might add, after all these years. I cannot find any schematics for the audio systems. Section 9 is divided by system such as lights, engine management, A/C etc. and all these sections have schematics. Audio has nothing! Seems to be a case of replace to repair. Did the swap routine and signals from the head seem to be good for both sides. Am going to order replacement amplifiers and maybe when I retire replace the electrolytic capacitors. I counted about 5 of them on each board. if you know the page number for the audio schematics in the manual let me know, regards, Rob