Rock-ola 444 - Distorted sound

[geeoff]

Hi, I disconnected the speakers when this was playing (it was working perfectly), I now have distorted/popping sound on both channels. Anyone any ideas, I suspect the output transistors...

[shrimpeater]

Has the amp ever been serviced? A amp this age surely needs service as per capacitors and yes,maybe transistors.
It's costly,but worth getting it serviced.It'll then be good for many years to come.
You can always change the transistors to see if it helps,but you will still have aged capacitors

[geeoff]

Thanks for the advice. I agree the caps probably need replacing and I will do that. Just seemed odd that it worked one minute and after disconnecting the speakers it didn't. Any idea what replacement output transistors to use. The existing are germanium.

[jukenorman]

This has come up before a few times, for example here jukeboxaddicts.proboards.com/thread/3831/rockola-40218-2-amp-transistors

Norman.

[geeoff]

Thank you, great info. I have done some further work this morning. I no longer have any real test equipment other than a dvm. But I managed to use an old radio with an aux input as a signal tracer, and I have found clean signal into preamp board and distorted coming out, so now investigating the pre amp.and looking for something common to both channels. not sure how the photocell lamp module works but that along with Q1 avc cct are going to get some attention!

[geeoff]

Hi all, I have found the fault it was IC 1 on the pre amp board, ordered and replaced. I am now going to recap the whole thing. Thanks for your help.

[jukeboxmarty]

Good news! Thanks for reporting back!