McIntosh Amplifier Heating Up.

[matciti]

Good day, I have an issue with a MA6600 amplifier.
The right output side where the cooling fins are gets hot when the amplifier is switched on (on standby no problem), as soon as I switch it on after 5 minutes it gets almost to hot to touch - it makes no difference if the speaker cable is connected or not or if there is music through-put, the result is the same.
The left side is completely cool to the touch as are the autoformers and transformer.
I have tried different output sockets and cables and results are the same. The amplifier is plugged into a dedicated line and my supply is stable.

I have been told that it is possibly that the output stage transistors need replacing as they can degrade over time ...?
I was wondering if anyone had a bit of advice or an opinion apart from just send it to a serve centre.
In case, am I correct to assume that transistors should be changed/replaced on both channels, not just one?

Thanks in advance.
Matt

[tdelahanty]

There is no need to change the transistors in the channel which appears normal. Transistors do not degrade over time as do tubes. If you have nothing connected to the overheating channel your amp needs a visit to a qualified technician.

[Cohibaman]

Originally Posted by tdelahanty

There is no need to change the transistors in the channel which appears normal. Transistors do not degrade over time as do tubes. If you have nothing connected to the overheating channel your amp needs a visit to a qualified technician.

+1

[Formerly YB-2]

Yep......... sounds like the bias or DC offset on that side is wacky for whatever reason and is running way too much current thru the output devices of that channel. Will guess that is an easy fix for a pro with the right gear to diagnose.

[tdelahanty]

I have one more question which may be relevant to this discussion. Is this amp in an audio-video system where you are using balanced and rca connections? Some A/V equipment is not truly balanced and must be used with rca cables with MAC.

[macman007]

If you have a good old digital volt ohm meter, you can measure the left and right channel DC bias. Most gear including Mc have a spec for setting the offset to. Experience tells me the DC bias should be as close to zero as possible if you don't know the spec offhand. Anything even approaching 1/2 volt DC or more needs looking at.

Typically the DC measurement on amps I've owned run between 15 and 50 millivolts, unless they were off and needed component work or adjustment..

Measurement check is easy. With all speakers disconnected, connect the multimeter set to DC volts on one channel output at a time. Positive to positive, negative to negative. Meter on set to DC volts, read the display. Do this for the hot channel and normal channel to compare. if nothing else, measuring gives you get an indication of what is going on internally, and the health of both channel's output stages, where most heat is typically generated.

The next step is measuring various specs and using dummy loads to simulate speakers and take readings. Nothing that a reputable shop with reasonable experience cant handle.

[Cohibaman]

Originally Posted by macman007

If you have a good old digital volt ohm meter, you can measure the left and right channel DC bias. Most gear including Mc have a spec for setting the offset to. Experience tells me the DC bias should be as close to zero as possible if you don't know the spec offhand. Anything even approaching 1/2 volt DC or more needs looking at.

Typically the DC measurement on amps I've owned run between 15 and 50 millivolts, unless they were off and needed component work or adjustment..

Measurement check is easy. With all speakers disconnected, connect the multimeter set to DC volts on one channel output at a time. Positive to positive, negative to negative. Meter on set to DC volts, read the display. Do this for the hot channel and normal channel to compare. if nothing else, measuring gives you get an indication of what is going on internally, and the health of both channel's output stages, where most heat is typically generated.

The next step is measuring various specs and using dummy loads to simulate speakers and take readings. Nothing that a reputable shop with reasonable experience cant handle.

One of the many features McIntosh employs in their solid state amps, including the MA6600, is the use of autoformers, which inherently eliminates nearly all dc voltage at the output terminals. You shouldn’t see dc voltage high enough to worry about.

http://www.roger-russell.com/mcintosh1.htm#autoformer

I’d definitely take it in and have a qualified tech look it over.

[stereo_5]

Something is definitely wrong. I run my MA6600 for 8+ hours daily and both heat sinks are only moderately warm. Time for a trip to the repair shop. It kind of sucks as it’s a very heavy integrated.

[matciti]

Wow thanks busy for all the replys and advice.
I have made an appointment to take it into a repair centre ... Only a 7 hour round trip

The amp is not part of an AV system, only a CD player as source and not using the balanced connectors.
For years it has been faultless and I can not remember it ever feeling more than slightly warm and it runs daily for hours.

I'll let you guys know what it was when the tech has looked at it.
Thanks very much.
����

[bdowell]

Years ago I had a Mc 7270 power amp that did the same thing. I was able to adjust the bias to factory spec with a volt meter. It was fine after. Best of luck.