No Stereo Indication on Model 105 tuner

[goldswimmerb]

Hey guys, I'm trying to figure out this model 105 tuner, I've downloaded the schematic and taken a look. I just cannot seem to figure out what is up with my stereo indicator. The light does not come on, even with a very strong stereo signal. I believe it is putting out stereo sound though.

Any thoughts? I noticed that the pin that is supposed to be for the indicator is always stuck at 0.56v I tried another chip from another unit and still had the same results, any ideas what could cause this?

 

[chazix]

You might want to say why you don't think it's simply a burnt-out lamp, because that's conclusion that I would leap to.

If I were to assume that the lamp is OK, I'd ask what is the voltage on both terminals of the lamp. There is what looks like a single-purpose DC power supply for the lamp.

Cheers,

chazix

 

[goldswimmerb]

You might want to say why you don't think it's simply a burnt-out lamp, because that's conclusion that I would leap to.

If I were to assume that the lamp is OK, I'd ask what is the voltage on both terminals of the lamp. There is what looks like a single-purpose DC power supply for the lamp.

Cheers,

chazix

The reason why I was saying it wasn't a burnt out lamp was because that was the first thing I tested, both with a new lamp, and continuity testing on the old one.

Got it fixed though, wound up being a failed diode in the power supply for the stereo indicator, replaced the diode and it came right back to life.