View Single Post
  #8   Report Post  
Posted to sci.electronics.repair
Tom Miller Tom Miller is offline
external usenet poster
 
Posts: 96
Default Old Technics tuner, anyone ... ?


"Arfa Daily" wrote in message
...


"Tom Miller" wrote in message
...

"Arfa Daily" wrote in message
...


wrote in message
...
I don't know specifically, but will check my service manuals on CD for
this one.
Any particular problem you are addressing? I may also have service
bullitens.

Dan


It has no 'proper' output. A bit of hum-y noise and that's it. Display
is normal. Appears to tune normally, but I'm sure it isn't. Looks like a
PSU problem or maybe a rail getting dragged down somewhere by a leaky
rail decoupling cap as used to be common on all sorts of Pan gear back
in the day. I picked one of the IF processor chips at random and looked
up the data sheet on it to find the Vcc pin. The sheet claimed a Vcc of
14 volts, but there's actually only about 5 volts on the pin. I tried
following the print back, but it rapidly starts jumping around the board
on wire links and print 'splits'. It's really not worth spending the
time on trying to trace where the rail comes from, and what decouplers
are hanging across it, but it would of course be a very simple fix with
the benefit of a schematic. If all else fails, I can get a download copy
for $4.99 of the 'net, but cheapskate as I am ... d;-)

Arfa

Have you checked the power supply bulk capacitors for a high esr cap?
Sure sounds like it could be an issue.


First check, always. Nothing jumping out. Main rail off the reccy is there
and looks about as ripple-free as you would expect pre the regulators ...

Arfa


Ok, yes. Knowing you, that was a dumb question. Good luck.