Radio Overhaul - Diagnostics page 3

Selecting the stereo left side speaker tone.

Decent stereo separation, so the decoder is working, but not the stereo lamp.

Next obvious step is to measure voltage at the lamp as maybe the bulb has simply failed.

Well I only get 2.3 volts for a 12 volt bulb. If I put my peeper right up to the amber jewel on the radio I can see a hint of glow in a dark room. I doubt the stereo decoder is so far out of alignment as to cause the dim lamp because it has pretty good stereo separation still. I bet it's the transistor or R70 or both even.

So now I know to pull and check that transistor and resistor.

Ok that hits all the key areas of the standard AM-FM stereo. I realize I'm skipping a lot and if there are questions on how FM stereo works or even how AM works (AM is real simple) I'll be more than happy to delve into it. Oh there was one more thing I failed to mention, the radio will not shut off. It's a physical problem with the On/Off Volume control. For whatever reason, it's stuck on and will not click off.

At this point, we can take apart the radio with a rational solid repair plan.

You really want to take copious amounts of pictures taking intricate items like this apart. This is true if there are many wires that must be unsoldered.

Here's some of the more interesting pictures.

This is one of the output amplifiers. It's a TO3 standard package, but geeze these look like the TO3 prototypes.

It starts getting unruly pretty quick.

There's the other channels amplifier output transistor. I've worked on a lot of vintage electronics and I've never seen this rendition of a TO3 till now. Learn something new every day.

Almost there.

That little board flipped up is the entire AM radio portion. The remainder large 'L' shaped bottom board is the FM and stereo decoder. AM radios are very simple and very open if you take off the top and very easy to work on. This is antithesis of that.

Ford offers integrated 8 track but with AM radio only for 1968. Now you know why. There's no bloody room for an 8 track player with the FM stereo portion.

This may look scary at this point, but if you take your time and loads of pictures it's not. There's no need to take this apart further. So we'll stop here and start the long road to recovery on the next round.