Pioneer SX-535 receiver - loud hum

[adrian]

Hi All

wondered if anyone can advise. A friend has an SX-535 that has worked well for some years but recently developed a loud hum that does not vary as volume is increased or decreased. I took a look today, and as I connected the right channel speaker cable (-ve) the hum kicked in and there was a spark between the amp's speaker connector and the cable.

I thought at first that there may be an earth problem, but the hum seems too loud for that. (by the way, how was 1970s gear earthed? Only via phonos?). My guess now is a damaged output transformer.

Opinions gratefully received. If an o/p traffo I guess the thing is kaput

Thanks

Adrian

[Nick]

I doubt if there are output TXs. Maybe one of the output devices has gone and connecting one of the rails to the speaker output.

Or there may be a output cap thats leaking.

[Dave the bass]

There are SS I thinkm http://www.cutesphere.com/data/people/g ... /index.php

I had one simillar in the w/shop for repair about 3 years ago. The owner had conncted the o/p of his TV to the LS o/p of the amp thinking it's save space by only having one set of speakers for both.....

One channels o/p transistors went leaky IIRC, found spares from a company we use called Mach5. The little bulbs behind the facia were blown too. Replacing them impressed the owner more than me finding the obselete transistors

DTB

[adrian]

Nick and Dave

that's helpful, thanks. Dave, what was the consequence of that leak?

Cheers

Adrian

[Dave the bass]

Nick and Dave

that's helpful, thanks. Dave, what was the consequence of that leak?

Cheers

Adrian

Leaky as in the silicon junctions of the devices go leaky (its an 'electronic leak not a fluid or otherwise leak) Instead of seeing a 0.6V fwd voltage drop betwixt Base-collector and Base Emitter you get a change. IIRC the PSU HT was down a smidge I guessed it was being dragged down by the faulty o/p devices.

DTB