Help - Faulty Marantz PM-4

[Bertiebee]

My amplifier was working perfectly well until Thursday evening when the right channel just cut out.

About 5 minutes later after a little crackle and it burst back into life (during this time it was playing on left channel only).

Trying again this morning and the right channel has gone down again - Houston, we have a problem.

The speaker cables are securely fastened (also if I tap the amplifier case with my hand this sometimes brings the sound back).

The problem exists irrespective of input (phono or tuner) but can be rectified by flicking mode switch from stereo to either mono or reverse.

Time for a service (know anyone good) or is it something simpler?

Thanks

Iain

 

[AndrewR]

Hi Iain,

It could be the mode switch itself - either a loose contact or solder joint.

Andrew

 

[reddish75]

I know this amp well as i've got one of these in the stages of being restored, try cleaning the switched and pots but its probably a dry/cracked joint, whether this clears the problem up or not if its completely original inside it will at least need a re-cap.

Chris

 

[Bertiebee]

Thanks guys.

Cleaning sounds like the first step - any suggestions as to what cleaner to use?

Failing that I might have to get the soldering iron out and have a look around the switch to see if anything is loose, broken etc.

 

[reddish75]

Use deoxit D5, the best, as far as getting the soldering iron out, don't bother just yet as some of the main board take a lot of dismantling to get too, if the cleaning doesn't do it, checking the preamp out with a scope and a signal generator would be the next part to see where the fault lies (pre or power amp) then take it from there.