Vintage amp maintenance

[TP143]

Hi all,

I have a vintage Marantz 1122DC amp that I pulled from the closet after a few years in storage and after hooking it up I noticed one of the channels was cutting in/out. To fix I would have to turn the volume knob back and forth until the channel resumed and it would play until the volume know was moved again (and I would have to start over). I pulled off the hood and found the interior to be quite dirty. I sprayed some deoxit and compressed air which cleaned it up somewhat but the channel cutting in/out is still an issue. So, to sum up my questions,

1. Would you recommend a more thorough cleaning than the compressed air? I have seen everything from this to disassembling and washing in water. If disassembling is required I would need definite direction/instruction.

2. What should I look for that could be causing the channel cutting in/out?

Thanks all!

[lanchile]

Lucky you! that is an easy fix!!! just go to Radio shack and get this spray tuner cleaner ( I do not remember the name) and spray the potentiometer and turn it a few times. easy as 1-2-3

[DigitalJunkie]

Even better,since he already has Deoxit,use that!

[lanchile]

Originally Posted by DigitalJunkie

Even better,since he already has Deoxit,use that!

lol..yeah I did not see it I read his post too fast. He just have to spray it and turn potentiometer many times to clean contacts inside it.

[Jebem]

Hold amplifiers like this one can get a lot of bad electrical contacts on all moving parts.
So we use a electrical contact cleaner (without grass or oil) of good quality that will not contain acids to attack the plastic parts of potentiometers and switches, and apply it to the offending parts.

However, it is not clear if the problem is just the volume potentiometer making bad contact... sometimes the output protection circuit, based on a relay, is doing bad contact as well and needs replacement, or if you can open it, clean it in the same way.

Service manual available for free (just register yourselves) at:
Download the Marantz 1122-DC schematic for free - Hifi Manuals

[TP143]

Hi again, thanks to everyone for the comments. My amp is working better but given the age (late 70s) I wanted to ask if I should be replacing any of the parts. I guess my question is if the unit sounds fine does it mean all the internal parts are working properly and no need to do anything or can part performance diminish over time but not be audible enough to give the listener a definite sense that something is wrong? If I should be replacing anything, is there a way to test the various parts using a multimeter or similar instrument to tell what is out of spec?

Thanks again all!

[Mooly]

Speaker relay contacts can be suspect too if it has them.

[sakis]

read this also .... it might be handy

vintage amplifier repair/upgrade manual