'92 with tape deck hiss

[Noobz347]

I have not done business with the company that I linked but if you read that page, they seem pretty serious and offer a warranty.

Once the unit has been messed with though, they generally won't touch it.

 

[bicknell]

Bah. Good news bad news.

I received the cassette deck manual. It has a troubleshooting guide, so I'd like to follow that and see what it suggests. That required getting the stereo out again. In go the removal tools, 4 clicks, pull.....nothing. A bit of wiggling and the left side came free. But the right side will not release. Lots of wiggle and jiggle, nothing. The latch just won't release.

I went ahead and removed the climate controls above as I was also planning to remove the airbag module to fix a different problem. I hoped that would give me an easy way to reach the clips and release it, but there are metal brackets all in the way.

Anyone have a tip on how to get the radio out without breaking it?

 

[bicknell]

I spent two hours watching bits of YouTube videos on radio work and console work in Fox Bodies. It looks like due to how that bracket is that holds the radio that my only option to try and remove it undamaged is to (mostly) remove the center console. While most people remove the radio before the console comes out, it looks like it would tip out with the radio in, it would just take a bit of a reach to get the wires disconnected. Once the console is out it should be easy to reach the clips with a screwdriver from behind and release them.

Anyone see a problem with that plan, other than an hour more of work?

It will make getting to that buried Airbag module a lot easier.

 

[Noobz347]

Keep on keepin' on.

 

[bicknell]

Ok, so I had to basically remove the entire console. Well, all but the last removal step. I wasn't sure how to remove the automatic shifter properly and didn't want to risk disconnecting that linkage, so it remained in place. I could still pull the console forward about 2 inches, which let me get a small screwdriver in where it needed to go to remove the radio undamaged.

With it out I see the problem. The radio removal tool has the notch about 1mm too far back. This means when the tool goes in that one prong on the right side goes in far enough to hit the metal case and not move. Now that I know, I can trim my removal tool a bit and it won't happen again.

I also have been talking to the person I bought the cassette manual from on e-bay....turns out his job was repairing radios for Ford for many years. He's now retired. An invaluable source of information and parts. Worst case he can sell me a replacement tape mechanism, but I'm working on the troubleshooting procedures with his help.

Now back to that stupid air bag module. Even with everything out of the way, man it's a huge PITA to get to.

 

[bicknell]

I figured you guys were due an update.

I did inquire with several places, including the one in the thread above. They were...expensive. Very expensive.

The guy I bought the manual from on E-Bay repaired these back in his working days. He's now retired and lost some of his eyesight so he can't work on them anymore. He has however been a wealth of knowledge.

I performed all the troubleshooting in the cassette manual, all was well. I consulted with him and he said his next move would be to replace the tape mechanism. He happened to have one which he sold me for really cheap. It came and I put it in. I would not recommend someone who doesn't have some electronics experience trying it. I do have some thought, and it was moderate difficulty. There is a 7 pin connector to de-solder and re-solder on the board, and then a 3 conductor wire with the signal from the tape head that gets soldered directly to the board.

Anyway, got it all installed and put it in the car and.....oh no. That dreaded "I let the smoke out of the electronics smell." Drat.

More troubleshooting and I discovered I had a solder bridge between two pins on the 7 pin connector which made a short straight to ground. Inspecting the board I found a blown out trace, turns out to be the trace brining power in from the battery. It was under the main power supply capacitor, which I don't think was damaged but was burned on the bottom.

Fixed the solder bridge. Ordered a replacement capacitor from Digikey. Fixed the trace with part of a connector pin. Installed the new capacitor. Take #2 in the car.

The AM/FM radio works as good as ever! Yay! I didn't blow too much stuff up. However the new cassette deck has.....exactly the same behavior as the old deck. The unfortunate conclusion is that the problem is not the TN-707 deck, but rather something to do with the tape circuitry.

The helpful e-bay man sent me a picture of the schematic for the tape section of the board. I inspected that section, looking real hard at the capacitors in particular. I can't see anything obvious wrong, no bulging capacitors, no corrosion. I know what the next step would be, powering it up and using an oscilloscope to figure out which component is bad. But, that's now beyond my comfort level on something this complex.

This whole time there has been a radio on E-Bay. It's the proper radio, same year. It is the one that goes with the graphics equalizer, but the seller didn't have that so it wasn't going for an arm and a leg. I decided to pull the trigger before it disappeared as these are extremely rare. It came, is in excellent condition and more importantly.....

It works perfectly. AM/FM and Cassette are all clear as can be. No hiss, no noise. Radio problem solved.

I am going to try and get the old one repaired. I think the guy who sold me this one refurbishes them so I've asked if he can fix up the old one.

 

[bicknell]

A final follow up here. Guy told me the radio wasn't worth repairing so he wasn't interested. I'm going to keep it as a potential source of spare parts down the road.