McIntosh mc2500 maintenance questions

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script56

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I have a MC2500 newly owned. The amp sounds great. A few issues im having are the power guard display lights are not coming on. There are the "limit" light which are red and "normal" lights which are green. I can't say for sure the limit ones aren't working because I have not reached a limit that would turn them on. But the "normal" lights, if normally come on during powering on, are not working. Are the lamp kits on ebay what I need to fix this? And is the procedure simple enough to be done myself?

Second issue is the dual fans are not running. Same scenario that I haven't pushed the amp hard enough to make them need to run, but I turned the switch on the back to continuos and they do not come on. Is this an issue? How could I fix it?

Any info appreciated.
 

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The normal lamps are either cm7381 or 7382 which are readily available for $1.00 or so.

For them to burn out after 10,000 hours of use is common.

It takes quite a load to get the fans to come on.
 
Thanks. Any idea of the disassembly instructions? Also on the fans, there is a switch on the back that reads "continuous", so I'm wondering if that would normally turn them on.
 
Do you have a soldering pencil and solder wick?

Once the top cover is off a couple of hex nuts allows the circuit board to be accessed.
 
script56 said:
I have a MC2500 newly owned. The amp sounds great. A few issues im having are the power guard display lights are not coming on. There are the "limit" light which are red and "normal" lights which are green. I can't say for sure the limit ones aren't working because I have not reached a limit that would turn them on. But the "normal" lights, if normally come on during powering on, are not working. Are the lamp kits on ebay what I need to fix this? And is the procedure simple enough to be done myself?

Second issue is the dual fans are not running. Same scenario that I haven't pushed the amp hard enough to make them need to run, but I turned the switch on the back to continuos and they do not come on. Is this an issue? How could I fix it?

Any info appreciated.
Click to expand...

I just picked up a MC2500 a few weeks ago. I thought the left channel power guard light was out. the normal lights are out too. However I found out different after pushing it at seller audition I could not light but right side. After getting home hooked up to my power sponge speakers XRT20 and XR19 hooked to 4 ohm tap different story. My yamaha pr amp which was good for 400 watts never could glow max power lights of both speakers cranked. The MC2500 will light them both solid. But boy does it take volume. There is a switch on back for preamp line voltage. Find out what your pre voltage is then match. I could not get enough gain with phono at upper setting until switching to 0.75 volt. Found my pre only put out 1.0 volt.


The fans will not come on unless you push this amp. A 4 ohm load set to close to 50 watts with peaks occasionally to 500 will warm it up after an hour or so to run fans. I flipped on continuouswhile one channel was hot and both fans kicked to high setting cooled amp to right now.


http://www.audiokarma.org/forums/archive/index.php/t-560811.html


Here is article if lamp replacement does not work. Have to replace transistors in the PG circuit.
 
Thanks. I have bulbs ordered. The fan although does not turn on when I flip switch to continuous. Any ideas about that?
 
script56 said:
Thanks. I have bulbs ordered. The fan although does not turn on when I flip switch to continuous. Any ideas about that?
Click to expand...

The MC2500 manual states with fan switch in continuous the fans will run on high anytime power is on. I would check voltage supplied to fans in continuous position if not there. Next I would ohm out the four position switch next if no power to fans to see if it is burned out or switch needs a deoxoit job. Multiple slides may return its function if corroded contacts. I would ensure inputs to switch are receiving voltage. Then trace to power supply circuits for fans. However depending on its past life the amp could have run with fans all the time thus they are shot now.

The manual says MC2500 is thermally protected and will stop playing if it gets too hot then restart at cool down. Not optimum for reliability if you are going to load this amp up with what it was designed to do. Recommend fixing fan problem to keep it trouble free.


Audio classics sells fans for 99 bucks.
 
If the fans don't work. fix them. I run both of my mc2500 amps in thermal mode. Takes about 6 hours before they come on assuming modest power levels.
 
Okay. Working the switch on the back panel up-and-down cleaned the switch enough to where the fans operate. So their functionality is confirmed. I believe the issue is in the switch or the wires. I have taken a picture of what I believe to be the power or the wire that connects the fans to the board. Is this something that I can spray with Deoxit to clean? Or do I spray the switch itself with deoxit? I use deoxit a lot with speakers but I usually don't work on amplifiers. I guess they are similar in some ways. If I push in on the fan switch then it seems to make them come on easier than just pushing down on it. It sounds like it is a contact issue. Any ideas on the cleaning areas let me know. Thanks a lot.
 

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For clarification the part in the picture that I am referring to is the piece on the bottom that is a round black piece with two metal pieces coming out of it with wire covering them.
 
You need to get the Deoxit into the switch.

The part you are pointing to is a heat sensor.....if the heat sink gets to hot it cuts the AC power on all the Mac amps I can think of.

I think there is a similar device on a different heat sink that switches the fans on. I think the wires are smaller.
 
script56 said:
Okay. Working the switch on the back panel up-and-down cleaned the switch enough to where the fans operate. So their functionality is confirmed. I believe the issue is in the switch or the wires. I have taken a picture of what I believe to be the power or the wire that connects the fans to the board. Is this something that I can spray with Deoxit to clean? Or do I spray the switch itself with deoxit? I use deoxit a lot with speakers but I usually don't work on amplifiers. I guess they are similar in some ways. If I push in on the fan switch then it seems to make them come on easier than just pushing down on it. It sounds like it is a contact issue. Any ideas on the cleaning areas let me know. Thanks a lot.
Click to expand...

Ensure amp is unplugged. Iwould spray deoxit on top of black slider hile working it. If back side of switch has any openings lik pot switches have spray deoxit into it and work it. Let dry 20 to 30 minutes until any deoxit has evaporated.

You should be good to go. Its nice when there is a easy fix.
 
Yes. Not too bad. I'll spray the switch from back panel. If that doesn't work I think the bottom panel of amp will have to be removed to access switch from inside.
 
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