Working on an Onkyo T-4 tuner, solid state. My S.S. training is pretty weak, but usually I can solve the problems on the older stuff. On this one there is a bulb that is supposed to come on when the station is tuned, called the TUNED LAMP on the schematic. ALL other lights work but that one, the bulb is good. If anyone can explain the theory on how that bulb should light, it would help me in troubleshooting. The tuning bulb appears to have about 32 volts on each side when off. Here's my theory---As the station is tuned in, one side drops voltage so there is a differential of about 6 volts, to light the bulb...right now it only drops about 2 volts differential..I might be wrong on this, so any help is welcome.....I replaced some of the transistors in that circuit, Q118,119...but no change.
Here's the schematic, but you need to be registed on the HIFI Engine website....
http://www.hifiengine.com/manual_library/onkyo/t-4.shtml

Got it....Apparently this tuner has a crazy 'touch sensitive' tuner knob circuit that interfaces with the
tuned' light function, and is adjustable by a switch for sensitivity. Just when you think you've seen everything...

:Got it....Apparently this tuner has a crazy 'touch sensitive' tuner knob circuit that interfaces with the
:tuned' light function, and is adjustable by a switch for sensitivity. Just when you think you've seen everything...

Sometimes asking the question helps you find the answer. :>)

True...but additionally this case I lucked out and found some original ads for that player on the web. They described that 'tuning system' to the prospective buyer, which was just a sales gimmick anyway. Sometime just plain luck (Karma, etc) plays a part too.

I also was extremely lucky in that Radio Shack actually had a bulb I needed for one of the tuning lights..What's the chance of that now-a-days?

Some time back I acquired a fancy SABA Freiburg radio that has ivory-colored plastic "piano keys" used to select the band. In overhauling the set I discovered that each key had a tiny incandescent lamp/switch assembly under it, to illuminate the button that had been pressed. Most of the micro-sized screw-base bulbs were burned out (I think that the "phono input" key was the sole survivor) and I despaired of ever finding replacements.

Amazingly enough, the first place I looked (Radio Shack) had these bulbs in the correct form factor, but wrong voltage (14 V versus 7V). I tried them anyway and found them perfectly acceptable- bright enough to be visible across a dimly-lit room, and will probably last indefinitely, too on the reduced voltage (a good thing, since they are not all that easy to replace).

I've heard that RS is on the skids and it's just a matter of time before they cease operations. That would be a shame... even though they are a mere shadow of the hobby-electronics store that they were back in the 1960s, they still have enough hardware components to make a trip to a local store worthwhile.

Most of the 20-somethings in the RS stores have no clue about the 'stuff' in their parts drawers. They wouldn't know a NPN from a PNP transistor (or what a transistor is). But I'm sure they can explain any iPhone function in detail. Times have changed. I actually tried to make them make good on a pair of their gold 'Lifetime' series tubes that were bad. They almost went for it, until they found the market price of replacing those tubes (they were now hard to get 79XX or something output tubes)..then they got smart and asked for the original sales receipt, game over.