FM 3 early Snr:

  • No one logged in.

30-Dec-2017 03:59 PM

PeterMisil

PeterMisil

Posts: 1

Hello everyone! My name is Peter, I live in the southern part of Sweden in Trelleborg. I'm new to Quad and this fantastic forum.

I have a 33 and 303 in great condition and working fine, I recently bought a FM3 with Snr:2870, a sticker on the underside indicates that it might have been serviced by Quad in 1978.

At first startup all the lights went on and station could be heard but with hum unless signal strength wasn't high. I have replaced the two PSU caps (1000uF/25V) and C113 (220uF/10V).

I have checked the voltage on the underside where it's supposed to be +-14V, I read 12V on my DVM! and after 30 to 45 seconds the tuner shuts off. It takes a couple of hours until you can power it on again and the same thing happends again. I have a pair of new zeners and a rectifier at hand, is this the right thing to replace them before anything else?

Fuses are ok, checked for bad solderings but can't find any and all out of ideas how to continue.

If anyone has a solution/idea about this please let me now.

Peter

  Reply

31-Dec-2017 10:38 AM

EJP

EJP

Posts: 1438

You're on the right track. Replace both Zener diodes in the PSU. The rectifier is probably OK but if the problem persists after changing the Zeners by all means replace it as next guess. Also check all the resistors in the PSU, and be prepared to change all the transistors in it as well.
  Reply