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MC225 transformer heat

@Alfmonster , if you contact them, asked them if they did any DC leakage testing...other likely cause is a carbon comp resistor way out of spec, biasing the output tubes too hard.....but would not continue running the 225 with the trans being that hot.

there sure seems to be excessive current draw somewhere. And keep in mind, back in the day, MAC designed these amps to run at full output for extended periods without overheating. In my collection of MAC amps, can't think of any that run that hot.

good luck, keep us posted on how it works out.
 
mcgjohn said:
@Alfmonster , if you contact them, asked them if they did any DC leakage testing...other likely cause is a carbon comp resistor way out of spec, biasing the output tubes too hard.....but would not continue running the 225 with the trans being that hot.

there sure seems to be excessive current draw somewhere. And keep in mind, back in the day, MAC designed these amps to run at full output for extended periods without overheating. In my collection of MAC amps, can't think of any that run that hot.

good luck, keep us posted on how it works out.
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thank you so much for this information, I will ask Ryan when I talk to him and also keep you posted as I monitor the situation. And I wanted to thank everyone else who took the time to give such great advice regarding this matter- can’t count on much these days but Audiokarma always comes through with so much generosity. Thank you!!
 
Alfmonster said:
Other MC225 owners, how hot does the transformers on your mc225 get during 6 hours of use? Mine stays warm to the touch for about 3 hours - Anything beyond that it gets hot. At around 6 you can still touch the transformer for a little bit - but can’t leave your hand on it like you could at 3hours.

I just had the unit gone through and repaired by AudioClassics a few weeks ago — is this an issue that should be looked through again or is this a known characteristic to the mc225 like the transformer in the mx110z?
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I have several 225s. They run warm but not hot. You may want to get an infrared gun and take some temps. Much more accurate than touch and they have come way down in price these days.
 
The 275 was the only amp being made by Mcintosh where you could touch the power transformer 99% of the time. MY 240's got really hot as did the 225, MC 30, 40, but not so much the MC 75. Another hot one was the MC 60 as I remember. Mine did anyway. I always used fans unless the amps were out in the open. I still use fans with my HT amps. The MC 830's are out in the open so its not necessary. WE had a lot of Dynakit 60 watt and Mcintosh 240's and MC 275's at the radio station. We could easily extend tube life by using cooling fans when the amps were Rack mounted.
 
twiiii said:
The 275 was the only amp being made by Mcintosh where you could touch the power transformer 99% of the time. MY 240's got really hot as did the 225, MC 30, 40, but not so much the MC 75. Another hot one was the MC 60 as I remember. Mine did anyway. I always used fans unless the amps were out in the open. I still use fans with my HT amps. The MC 830's are out in the open so its not necessary. WE had a lot of Dynakit 60 watt and Mcintosh 240's and MC 275's at the radio station. We could easily extend tube life by using cooling fans when the amps were Rack mounted.
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Hummm...my MC240, fully restored, and another one (in original, but sold ), and MC30 (serviced, but not restored) are just warm after many hours of running.
 
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