Bad tuner

[DaveWM]

ok pretty sure the tuner is bad in my zenith console PN 175-589 zenith.

I say this since tube swap does not help, IF feed to tv results in perfect pic.

the balun is burned up (open and one side looks cooked). My guess is lightning strike.

Anyway anyone have any luck fixing a tuner? What am I looking for?

Is there a way to either replace or bypass the balun, assuming that is the only problem.

I get a snowy interference laden pic.

I could of course just bypass the tuner completely and put in a RCA connector for a composite video, but I like to have things that work.

Seems like such a waste to have all those un used tubes...

[Don Lindsly]

You can bypass the balun by connecting 75 ohm directly to the balun output-RF input. Use a series capacitor around 500-1000 uuf between the 75 ohm center and the RF input. Use another cap between coax ground and chassis ground if the TV has a hot chassis or make sure you use an isolation transformer. It's a little sloppy, but it works.

[miniman82]

Originally Posted by DaveWM

Seems like such a waste to have all those un used tubes...

So pull them out- that's what I did on my Philco, and the picture was better than it was through the tuner!

[DaveWM]

Originally Posted by Don Lindsly

You can bypass the balun by connecting 75 ohm directly to the balun output-RF input. Use a series capacitor around 500-1000 uuf between the 75 ohm center and the RF input. Use another cap between coax ground and chassis ground if the TV has a hot chassis or make sure you use an isolation transformer. It's a little sloppy, but it works.

Tried it, no improvement.

I may try the B&k 1076 again, this time injecting the signal at at different points around the RF tube and the osc.

I got a line on a tuner from a fellow over on ARF so I will go that route.

as far as bypassing the RF/IF, yes I know it produces a better pic, but I just dont like doing that. Of course I may change my mind after I run out of ideas/options on what to do to fix it.

[radiotvnut]

Does anyone know if Quality Tuner Service is still around? I talked to them several years ago and he told me that with TV going digital and the fact that analog sets were so cheap, his tuner rebuilding business had really suffered. However, he was still rebuilding tuners part time. And, I think he was still accepting older tube type tuners for rebuilding.

[DaveWM]

some where in here is a thread and yes was still rebuilding I even called him maybe 6 months ago...

one dumb thing I did not even check is the AGC setting.

[DaveWM]

its seem more like interference than snow. I think its time to scope the B+ and make sure I dont have some trash coming thru there.

but since when I feed the IF it would have to be decoupling on the the tuner B+

[DaveWM]

progress..

made up new balun, installed. I just used reg magnet wire and attempted to duplicate the windings (four coils of 6 turns each two coils interlaced).

adj AGC

moved DVD player (not sure why but that had an effect on the interference.


Looking much better now.