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MCS Left Channel No Sound.

Uno Castillo

Uno Castillo

Member
Hi i just get a MCS 3275 but it has a problem. Left channel it si not working. the power meter doesn´t move in the left channel.

I moved the balance button all the way to the left and turn up the attenuator, the tweeters sound, but there is a poor sound. Right channel sound Excellent.

A technician told me that it could be a damaged circuit. it is that possible?

I have read that this kind of Receivers tend to have this kind of problem.

It is easy to fix? could it be something problematic? would it need something more than a deep cleaning?.
 
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Most likely it needs the controls cleaned. All of them. Even the a/b speaker switch.
The 3275 and 3125 are known to suffer channel dropouts due to dirty controls.
Especially trouble prone are the tone defeat switches but if disassembling it's best to clean all the controls because any of them could be dirty.
I've done a couple of 3125's, the most difficult part is removing the two equalizer tone control boards. I suspect it would be the same with a 3275. Because of that it's best to clean all the controls at once, much better than having to tear it apart more than once.

Maybe first just work all the controls through their motions, knobs from end to end of travel, and switches off/on MANY times. Do this with the volume and bass/treble turned down but loud enough to know if the channel starts working.
In fact that may make the left channel start working and will clue you in on which control may need extra attention.
 
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goodolpg said:
Most likely it needs the controls cleaned. All of them. Even the a/b speaker switch.
The 3275 and 3125 are known to suffer channel dropouts due to dirty controls.
Especially trouble prone are the tone defeat switches but if disassembling it's best to clean all the controls because any of them could be dirty.
I've done a couple of 3125's, the most difficult part is removing the two equalizer tone control boards. I suspect it would be the same with a 3275. Because of that it's best to clean all the controls at once, much better than having to tear it apart more than once.

Maybe first just work all the controls through their motions, knobs from end to end of travel, and switches off/on MANY times. Do this with the volume and bass/treble turned down but loud enough to know if the channel starts working.
In fact that may make the left channel start working and will clue you in on which control may need extra attention.
Click to expand...

How do i clean it?
 
I would first try working all the controls manually, end to end with knobs/dials and on/off for switches, many many times each one.
You do not need to take anything apart to do this.
Some you could have the receiver turned on (but have the volume and bass/mid/treble settings turned down low) but you don't want to run the volume knob end to end with it powered up for obvious reasons. See if that restores the left channel. If it does and you know which switch made it work then that might be the one and maybe it will work but may quit again in the future.

If that does not get the left channel working then I'd try cleaning all the controls.
As for cleaning the switches, how handy are you? At minimum you will need a screwdriver and a small allen wrench, also some deoxit or CRC Quick Dry contact cleaner. The top, faceplate, and maybe the bottom cover of the receiver will need to be removed (the tuning knob and maybe the volume/balance knob MIGHT be held on with small allen head screws).
It's going to take some time, like 2 to 4 hours especially the first time you do it.
Care must be taken to not have the tuner dial string come off, putting tape on each wheel or contact point the dial string contacts is probably wise.
Here are a couple links, one for Deoxiting/cleaning in general
http://www.audiokarma.org/forums/in...diots-guide-to-using-deoxit-revisited.207005/

Here's one for cleaning 3125 controls, your receive will not be exactly the same but it will give you a general idea what is involved.
http://www.audiokarma.org/forums/index.php?threads/mcs-3125-control-cleaning.49994/

If you are not comfortable doing the cleaning yourself it might be wise to have a tech do it.
Cleaning the controls is not guaranteed to fix your receiver but it has fixed many MCS units in the past.
 
Thank you so much for your answer. I moved all the buttons and leves and knobs, but it doesn´t woke up.

I am not that good on tech, besides i don´t have the proper tools to do the job. I took it to the Tech. He said that the amp was ok, but with some minor problems on a few parts on the left channel cicuit, he says he could replace them and the amp will work properly, of course he can´t replace de circuit because we can get a new one. But he says he are going to change the parts that need adjustments .

that is where i am so far.
 
Hopefully the tech get's it going for you.
If unsure better to let the pros do the work.
Like you mentioned, you'd seen where these can have that type of problem. It is quite common.
Both of my 3125's came needing controls cleaned due to channel dropouts. I was able to get them both working ok.
But then one of them went into protection a few months later and did need some small electrical parts replaced so I took it to a tech. Too complex for me plus I don't have the proper gear for that.
I guess that's to be expected since they are around 35 years old now.
Good luck, hope it's working right soon!
 
Well i got it from the tech. The Left channel it´s alive but it needs a good cleaning sesion because many buttons and controls are making noises. the "defeat" buttons of both EQ need special attention you have to move them in order the EQ make its work.

So, i am going to begin my year cleaning my Old "new" beast. i have to say that its sounds its just great.

I have a Pair of Bose 203 Series III. And i think that those aren´t making it any justice to the amp.
Any recommendation on new speakers?
 
Uno, I've had two of these, not the exact model, but same series that had one channel problems. On one a channel was not working at all and the other one there was one channel low and scratchy. Although I did a thorough cleaning on all switches and pots, it turned out to be the Stereo/Mono flip switches causing it. I assume because this switch was/is seldom moved in 30+ years or something. It took a couple of good blasts to get these switches cleaned up. Channels came back and sounded pretty good al in all. Just my couple of cents for what it's worth. Good luck and if I, or anyone on AK can help you out, just holler.

Bubba57
 
Like I mentioned, I cleaned both of mine when I got them and it fixed the channel dropouts.
I try to use them occasionally, one is hooked up as a "display" system and I play it at least once a week just to make sure everything is fine.
The other is "resting" with other spare gear and I turn it on every 2-3 months...one time that one had a channel dropout (again), it was the a/b speaker switch that time. Bubba57 mentioned his had the stereo/mono switch act up.
That's why my first post mentioned cleaning ALL the controls. While some are more prone to problems it seems any of them can act up.
Once cleaned and working it's not a bad idea to run the unit and work the controls every so often.

Uno, I don't know how easy it is to get at the two lights that illuminate the power meters. I do see 3275's for sale quite often that have one or both lights out. You might want to replace those while you have the unit apart for cleaning.
If they are both working at this time you could leave them in. They could last another 2 weeks or 20 years....who knows.
 
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oh no. this its no working at all.

i put some deox on controls, and now it doesn´t sound.

Every button I press makes a terrible sound
like the speakers are going to explode. no radio signal, no aux, no nothing. i dont know if i damage it. i didnt touch nothing, just deox on every button and switch. that was all.

¿it has been like 300 minutes since i apply the deox. please help.

did i broke my amp? i would need to "dry".? :(
 
Uh oh.....Deoxit does need time to dry before applying power, but I would think 300 minutes would be plenty of time. Which controls did you clean? Maybe we can figure it out. Tip it up on it's side to allow all the cleaner to drain out and dry (an hour or two), and then try switching it on again. Are you then able to tune in a radio station, and see the power meters move as you turn up the volume? Maybe it's the speakers. Can you try a pair of headphones to see if you get sound? Check the obvious switches - for their position. Make sure the tape monitor switches are in the source position and the Dolby FM button is out.
 
Everything looks okay in the video - except I would guess the problem is with the tone defeat buttons. They either are still very dirty, or maybe they have somehow shorted out (just a guess). I would try and clean the defeat buttons a few more times - as thoroughly as possible - and let it dry out before switching the power on. Also - I would suggest hooking up a "crappy" pair of speakers - if you have them. I wouldn't want anything bad to happen to your good speakers. OR - and this is a guess - maybe the issue is with the main fuse on the rear panel. Can you unscrew it to see if it is still okay? It may have blown somehow.
 
But do you ear that there is no sound ?

Just tha dirty sound and when press the defeat control PUUMMM.

I don't know where is the main fuse .

Yes I am using a crappy speakers to do the test
 
I hear that there is no sound - that is why I think the tone defeat buttons are still dirty. On the MCS 3275 and 3125, these defeat buttons are just REALLY hard to clean correctly. It takes many, many cleanings before they operate correctly - and let sound pass through. I would spray cleaner into the switches, then work the buttons in and out many dozens of times - and repeat this several times - before the issue would clear up. It's very frustrating, but they can be cleaned with some patience. I have two of the stand alone equalizer like the one built into your receiver, and the buttons need cleaning every few months after sitting a while.

After getting the cleaner into the switches, just push those two buttons in and out many, many times. It is very repetitive, but necessary, to get them clean.

Also - not to discourage you, but other switches will also need the same attention - to ensure they are clean. The Dolby FM button, also. Even if one switch is dirty, you will lose all sound in one or both channels. Once everything is properly cleaned, the sound should be fine.

Also, the fuse in the back is probably fine - because you were hearing a thump, or PUUMMM through the speakers. If the fuse was blown, there would be no sound at all.
 
Holy crap - WD-40 is NOT what you need. You need electronic contact cleaner. Keep the WD-40 far, far away from electronics.
 
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