MCS 3275 Troubleshooting

[cassette]

Hi all,
So I won a Shopgoodwill auction on a vintage MCS 3275. It Is pretty awesome looking with the ridiculous amount of knobs and lights. One problem though, the left channel isn't producing any sound. I followed the idiots guide to using DeOxit (twice) and there is still no sound. Any suggestions on what to try next? Is this worth investing any more in (as in taking it to a repair service)? Thanks for any help!

A

 

[goodolpg]

Most times it is dirty controls.
The two defeat switches are known to get dirty, but any of the controls can cause a drop out.
If cleaning the controls do them all and do them well. Make sure the solution reaches the contacts and work the switches full range many many many times.
Both my 3125's needed controls cleaned, first time for the defeat switches, a few months later the speaker selector switch in one needed cleaning.
Most times a thorough cleaning will do the job. The deoxit needs to get inside the controls, a spray and pray won't get it done.
While it's a pain removing the EQ switch sections that is the best way to ensure a good cleaning of the eq and defeat switches. Not sure about the volume control in that unit, in the 3125 it needs to be accessed and one of the screws that hold the control together must be loosened/removed to get deoxit into the contacts themselves.
Good luck.

 

[Hifirob2]

On this model, two rounds of Deoxit may not be enough. Try three more intensive rounds - paying close attention to the tone defeat buttons, Dolby adaptor, FM mute, tape monitor, and function switches. Manually work the volume control throughout it's range a hundred times (since getting deoxit inside is tough to do properly). Check all inputs to see if the problem follows. If still no sound, then yeah, a trip to a tech may be in order.

What it's worth to you - I can't answer. Sold ebay listings say this model is worth it.

LOL - goodolpg beat me to it while I was typing......so, yeah - what he said

 

[cassette]

Ok, thanks for the input. I have been trying to be as minimally invasive as possible, but as much as I love the spray and pray philosophy, it may take more work. I am a little worried about 'ruining' it by taking too many pieces parts out, but then it doesn't really work now, so I have nothing left to lose! I will keep everyone posted. Thanks again!
A

 

[goodolpg]

There's quite a few fans of those MCS receivers, well worth fixing if it can be done cheaply.
The hardest part about the 3125 is removing the EQ boards, while not sure I suspect the same would be true with the 3275.
The actual EQ and defeat controls are on the bottom of their respective boards, not sure if access can be done by removing the bottom plate of the receiver. If not, removing the boards may be needed.
While sort of flexible they aren't rubber so care should be taken with the amount of flex applied to remove them.

Here's something you can try, dry or with cleaner/deoxit (deoxit probably raises the chance for success), probably best with very low volume or the unit off (with low volume it might enable you to hear which switch is the one causing the channel drop out but I'd be very cautious, with the unit off you have almost no risk of "blowing it up" but you may find the problem fixed but won't know which switch was "bad") just work each control and switch back and forth and back and forth and back and forth.
All controls and selectors. Switches turn off and on, knobs turn end to end.
Won't hurt anything and might just "fix" it.

 

[cassette]

ok, finally got around to it more. When I have it in Stereo mode I get one channel. Switch to Mono and I get sound of of both sides. Funny thing is right next to Stereo/Mono switch there is an AF Mute Switch. It can also turn it into a point where only 1 channel works. These are strange things.

A

 

[goodolpg]

For whatever reason some MCS receivers are known to get dirty switches and channel drop outs.
Did you clean all the switches, get cleaner inside them, and really work them as part of the process?

After a good cleaning I put one of my 3125's in "retirement", but was turning it on every 6 months or so and working all the controls.
One time I had a dead channel.
It was the Function switch (FM, AM Phono,etc) or the speaker selector switch that time (A, B, A+ B, etc). And yes, they had all been cleaned previously.
That's why I always urge someone new to the MCS 3275 and 3125 to clean ALL the switches, and do it well as taking them apart isn't much fun IMO.
My second one is in a small second system, I run it at least once a month and work the switches, hoping to keep them all working.