well i just tried this, and after reassembling the unit i have two major problems:
1. the line input level is way too low
2. the volume knob on my HU no longer works

i obviously screwed something up, so there are dangers here

@ZOwl
Sorry that it hasn't worked for you.

However I doubt that the mod to the cassette module would have any direct effect on the master volume control (assuming that no pretty obvious damage was done to the main PCB when the unit was in pieces).

My guess is that the front panel has not reseated correctly (maybe some of the contact pins were damaged/bent when you removed it) hence the non-functioning volume control. Can you remove it again and reseat (after checking that all the connections are visually OK).

Cheers

Eric

I removed and reseated it. The pins looked fine, I didn't see any issues. All the other buttons are working properly, but the volume knob still has no effect.

Check to see if you have an exposed wire, I did this mod, and it worked perfectly, it's odd that your getting this problem.

Do you only have a problem with the volume knob when it is in "Tape" mode?

No the volume knob does not work in any mode. Luckily the volume was set at a comfortable level before it went bad so it's not killing me.

What do you mean by exposed wire? Which wire?

the connection that you made to the cassette player

The clearance between the metal bulkhead across the headunit and the soldered connections is pretty tight when the cassette assembly is back in place. You might be getting a short to ground there (which might explain the low gain on the tape input).

Try putting a piece of insulating tape over the three solder blobs to make sure that they're not touching anything.

Cheers
Eric

Well I've found both problems. I had a bad ground on the input line which resulted in the low line level, that has been fixed.

The volume control was a different issue. I had accidentally scratched the PCB on the back of the faceplate while trying to remove it initially, and I had cut one of the lines from the volume knob. I will get that fixed by a friend of mine who is a pro at working with PCBs.

Re: blahblahblah
 

Would it be possible to completely remove the tape assembly from the BOSE unit and fool the unit into thinking it is still there? Line In's (and fooling stuff) could then be attached to the exposed connector with a cable/pcb? without damaging the circuit board at all. i.e. a 'plug and play' solution :D

You could also probably tie in to the other i/o and build an interface to control your mp3 player (iPod etc) from the controls on the HU.

Now that's something I'd pay for :D

I am not about to do this, but for those working on it, just an idea.

Noise from the tape unit could/must be generated by the motors trying to "turn" the tape. Sooo... how about you disable the motor while you are in there? You might still need the "dummy" tape, but you won't get any noise if nothing is turning/moving...

Just an idea. Very interesting thread! :)

Well I've had the faceplate repaired and now I'm up and running 100%. It works and I'm happy with the result. Plus my empty nav compartment is a great location for an MP3 player.

@Zowl
Glad you're sorted.

@slaponte
Cassette decks check that at least one (and probably both) reels are rotating to prevent the capstan and rubber pinch wheel stretching the tape in the eventuality that the tape becomes jammed. It's not enough to disable the motor, you need to convince the deck that the tape is moving or it will stop and mute the input.

Cheers
Eric

Maybe I am old, but this used to be done via a mechanical sensor that rested against the tape. If the tape stopped moving it would push the sensor "out" and it will trigger auto stop.

Now, given new age technology, they might use an optical sensor or something like it to check for movement. I thought this unlikely since it would add cost to a cheap unit... but who knows.

My thought was that any "noise" on the line would come from the spinning motors, so if you can make them not spin you probably get rid of the noise.

Sorry, didn't mean to "dirty" up the thread with unfounded thoughts.

@slaponte
You're not dirtying at all, ultimately as the Bose is back in my Z and isn't coming out again its just my opinion. I've always thought the reel movement was detected directly on the reel that the tape is spooling from or both but I'm happy to be proven wrong.

Cheers
Eric

I'm happy with it in this state as well, I don't plan on taking the deck out again. Although, there is some noise from the power supply for my MP3 player. Its a 12V/5V step down car adapter. Any ideas on how to filter out some of that noise?

Maybe I'm missing something here, but it seems to me that it's entirely possible that the muting of the cassette input may happen before the signal gets to the solder points as previously shown. If that is correct, wouldn't you be able to avoid using a cassette adapter by piggybacking the new input wires to the shown solder points and not cutting the existing solder lines. You could still use the cassette player as intended or your new iPod, etc. input, but not both at the same time because of signal overload.

wat if you took an old tape and ripped out the internals and stuck it in there? That might cut down on some noise within the cassette deck.

Unfortunately not. If this were the case then the piggyback signal would work without a cassette in the cassette deck irrespective of whether the traces were cut. It doesn't. With the auxiliary source playing you need a dummy cassette in order to hear the output.

are fm modulators that bad?

i just purchased a ppl digital fm stereo modulator with built in ground isolator ic and anti howling system. im still debating on wheather or not i want to go the modulator route or the tape deck route. i have yet to use the tape deck in the 2 years i've had my z so its not like im worried about the losing the tape deck. however the fm modulator will save me a lot work. this whole thing is for hooking up my xbox into my stock nav screen and getting sound threw the stock bose system.

basically my questions is, what do you guys think? modulator or tape deck and why? thanks.