MA 6100 problem, grrr, again..

My MA 6100 was serviced recently, as it had a bad balance pot. Everything was working great until about 2 days ago. Not sure if this is something really basic (I know next to nothing).

The left channel distorts heavily, but, when i disconnect all the speakers (or turn them off, both remote and main), the sound is perfect through the headphones. I assume this means the amp and pre are fine? But why does the left channel distort again as soon as I hook up a speaker to it (right channel is fine, speaker is fine also)?

:tears::tears::tears:

Sorry to hear about your problems. My 6100 started acting up a few months after Terry worked on it. I am getting a lot of noise and drops the right channel. I cycle the volume knob and that usually clears it. If it doesn't I have to mess around with those jumper cables between the per and the amp. I'm going to try deoxit on these connections. I don't know anything about fixing these things but I think the headphones come off the pre amp not the amp. Like I said though I really don't know. Perhaps one of the more knowledgeable folks here could set us straight.

thanks for reply.

yes, ive tried bypassing the preamp, same problem. messing with the pots changes nothing. thats why im so confused. sound is great through headphones when no speakers are connected, also when the right channel is connected to speaker. but as soon as i connect the left channel to a speaker (from remote, or main) it starts to distort (also in headphones). as soon as i disconnect, sounds good again.

It sounds like the load you are putting on the one side causes the amp to distort... the headphone load is not enough to affect it. First I would swap L and R speaker wires at the amp to make sure it is not the speaker or wire distressing the amp. IF still distorted in original channel probably a failing output transistor is breaking down.

yes, as i change the speakers/wire, the original channel still distorts.

I guess that when these units get over 30 yrs old it would be wise that when we send them off for repairs we should get them refurbished instead. I think that would save the heartbreak of it acting up, and pain of repacking and reshipping. For an extra $100 or more you could get a lot of new components installed and be done with it. All you need do then is enjoy the great sound.

lissjw said:

I guess that when these units get over 30 yrs old it would be wise that when we send them off for repairs we should get them refurbished instead. I think that would save the heartbreak of it acting up, and pain of repacking and reshipping. For an extra $100 or more you could get a lot of new components installed and be done with it. All you need do then is enjoy the great sound.

Click to expand...

I concur.:thmbsp:

Did you ever figure out what the problem was or how to fix it? I have the same problem and it sounds like this guy did too...

I got my amp as a hand me down and I know it was put away working but after coming out of storage the right channel is now distorted - kind of like a blown speaker. :thumbsdn:

Sitting around in storage does these units no good...certainly worse off than using them everyday.

I am currently finishing up a unit that sat for 10years or so.. needed all new small signal electrolytic caps. all ground drains bonded, new grounding scheme implemented , and the volume control disasembled to clean the internal brass contact surfaces. Still has a preamp transistor that is a bit too noisy so will replace those also.

Is it worth it? Absolutely, sounds wonderfull now even if still a bit noisy because of the tranistor.

This is probably not a fix for the bigger issues of a '6100 that is in need of a rebuild, but it might solve the problem temporarily until you can get it serviced:

Try removing the top-side boards, cleaning the connectors, and then swapping the boards for a better "seat" when replaced.

I recently rescued a "barn find" MA6100 that needed serious top-side cleaning that involved removing all the top-side cages and boards. Though it actually worked fine before cleaning, it exhibited the very symptom you described once it was reassembled - bad distortion in one channel. I figured the cleaning actually made something worse, so I went in for more.

What I did:
Once disassembled, I vacuumed the connector slots carefully and thoroughly with a soft-bristle brush attachment. I then cleaned the connector slots by cutting and folding paper towel over the edge of a credit card. I soaked the edge in DeOxit and worked it gently up and down in the slot to clean the connectors. I then cleaned in the board contacts similarly, with paper towel and DeOxit. When I reassembled it, I swapped board locations, thinking that a fresh slot might offer better "seat" for the connections.

It seems to have worked - it's singingly happily again! Now for a rebuild ...

Well, the distortion returned to the left channel after several days of gentle to moderate use. I opened it back up to re-re-seat the boards (about the only thing I could think of before delivering it to a qualified repair tech across the state) and I noticed a blown fuse underneath. (see pic) I replaced the fuse and it's singing, again.

Obviously something caused the fuse to open, so there is probably a lingering problem someplace and it's still destined for a re-build soon. However, it's back on-line for the time being.

The fuse that was out was the lower-right fuse. (The new one looks ever-so-slightly shinier.)

Mcintosh MA 6100 Fuse

Did you ever find out why that fuse opened up or has it played nicely ever since?

I was just curious what caused that. Thank you.

MA6100 problem grrrrr again

nikbee said:

My MA 6100 was serviced recently, as it had a bad balance pot. Everything was working great until about 2 days ago. Not sure if this is something really basic (I know next to nothing).

The left channel distorts heavily, but, when i disconnect all the speakers (or turn them off, both remote and main), the sound is perfect through the headphones. I assume this means the amp and pre are fine? But why does the left channel distort again as soon as I hook up a speaker to it (right channel is fine, speaker is fine also)?

:tears::tears::tears:

Click to expand...

Hello Nickbee

I think you have one fuse blowed on one channel and this fuse is out because of a bad driver transistor like 132021 (yellow dot) or 132032 (orange dot) . One of these both defect make one output transistor bad and so the fuse burn .

Don't make comparison with headphone because the headphone is not asking enough power from the output stage on the MA6100 ;