TV6 Problems

[SurfSire]

I assembled and was ready to test my TV6, but when I plugged it in one of the 2N3904 transitors (Q4) started to smoke. I assumed it was a short, and unplugged and checked for solder bridges, but found none. I replaced the transitor, and resoldered the 'less than perfect' points, along with checking polarized components. But it still smoked... what should I check for? Or is it a lost cause?
All ideas are welcome

[Ramsey Tech Z99]

You have a short in that circuit somewhere. Verify R10 is 10 kohms. If you have a multimeter check the caps for shorts. Use the foil diagram and check to make sure no foil short exists.

Good Luck!

[juz10mac]

Hello,
I think I might be having a similar problem, just not to the extent you do. My Q4 transistor runs hot. It doesn't smoke, but it is hot to the touch (about like the voltage regulator or the metal-bodied Q5. I'm assuming this is not normal operation. I can tune in a picture from the TV6 on my television, but It is hard to get the adjustments right and I can never get a picture I'm happy with. Could something be wrong? I verified all the solder points for continuity and I verified the resistors, but I have no way of verifying the inductors, capacitors or transistors. Is there a common component failure that causes this problem? Did you ever find your problem? At very least could someone verify that the Q4 transistor is not supposed to be hot.

Thanks,
Justin

[juz10mac]

There are a couple of things I forgot to mention: I get audio, but there is a loud popping sound throughout the broadcast. Also, the only channel I can test my setup on is channel 3 (channel 4 and 5 are in use by local broadcast stations and I cannot get a picture at all on channel 6). I have also checked for shorts and found none. Does anyone have an idea as to which components could cause such a problem if not functioning properly? I appreciate any help.

Again thanks,
Justin

[hector2004]

I had that same problem last year. I just gave up. Costing me too much money to get it fixed.

[juz10mac]

I found the source of the problem with the Q4 transistor (or, at least, the source of my problem with it). When I was trying to get a channel adjustment I would raise and lower the slug on L4 to find the right frequency. But in the process of moving the slug around, I positioned it too high and it created the wrong frequency response. The impedance seen by Q4 was too low and it shorted (causing it to heat up). I replaced the damaged Q4 with a fresh transistor and I made sure to leave the slug in a low position. I get a much better picture now. Be careful not to raise the slug in L4 too high! There is still distortion in my audio, but I think this is an unrelated problem. I'll let you know if I ever figure that out.