Hello to the Forum
Some months ago I bought an all original McIntosh MC502 power amp, untouched. Yesterday I finally had the time to unpack and test it.
Althought it works perfectly, apart from the L channel protection "Normal" indicator which seems burnt (I'll investigate on that soon), the main problem I have is the transformer buzzing...very annoying.
I plan to use this amp in a mini setup for my working desk, where I always keep the volume at minimum. Humming and buzzing is something I cannot live with. I already fired a Cary SLA-70 for that.
I've tried to access the transformer to see if it was possible to tighten the laminations screws but it is completely buried in resin. No way to go, unless using brute force, which is something I'd like to avoid, since the box is well finished, with McIntosh logo and connections legend.
Trying to insulate the chassis from the trafo box did not help.
I am now wondering whether it would be possible to completely remove the resin+trafo and replace it with a modern toroidal one. In this way the look wouldn't change (maximum attention shall be to put in order to avoid damaging the trafo box finish) but it should go completely silent and, possibly, with slight better current delivery.
Did anybody ever try something like that?
Do you guys believe it is feasible?
Thank you
Bye
Raf
Some months ago I bought an all original McIntosh MC502 power amp, untouched. Yesterday I finally had the time to unpack and test it.
Althought it works perfectly, apart from the L channel protection "Normal" indicator which seems burnt (I'll investigate on that soon), the main problem I have is the transformer buzzing...very annoying.
I plan to use this amp in a mini setup for my working desk, where I always keep the volume at minimum. Humming and buzzing is something I cannot live with. I already fired a Cary SLA-70 for that.
I've tried to access the transformer to see if it was possible to tighten the laminations screws but it is completely buried in resin. No way to go, unless using brute force, which is something I'd like to avoid, since the box is well finished, with McIntosh logo and connections legend.
Trying to insulate the chassis from the trafo box did not help.
I am now wondering whether it would be possible to completely remove the resin+trafo and replace it with a modern toroidal one. In this way the look wouldn't change (maximum attention shall be to put in order to avoid damaging the trafo box finish) but it should go completely silent and, possibly, with slight better current delivery.
Did anybody ever try something like that?
Do you guys believe it is feasible?
Thank you
Bye
Raf
Just send it into mcintosh. They are reasonable and will warranty it. I have sent them entire amps and had them come back in factory spec for $400.
I mean you bought a Mcintosh amp because you wanted a Mcintosh amp. They will treat you right.
I mean you bought a Mcintosh amp because you wanted a Mcintosh amp. They will treat you right.
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I'd immediately go if I was in US...
Here in Italy the situation with Macs is quite discouraging.
The one known to be "the best" is not even the official one, since the importer has quite a peculiar market strategy.
I'm sure €.400 won't be definitely enough for an original Mc trafo here.
Here in Italy the situation with Macs is quite discouraging.
The one known to be "the best" is not even the official one, since the importer has quite a peculiar market strategy.
I'm sure €.400 won't be definitely enough for an original Mc trafo here.
You can buy direct from them from where you are and have them ship it. Call them up and ask. Or I will if you like and let you know. If they won't drop ship ( which I am sure they will) I could help find you another option.
Do they really sell directly? Quite unusual and really great.
jwags818, you're so kind in offering you help, but I don't want to be a bother.
If they can't ship to Italy due to an agreement with the local distributor, I will let you know.
What is the best way to call them? I'd just have to go with the phone numbers on the site?
My only fear is that this buzzing is kind of normal for Type 045416 trafos. Don't really want to buy a new one just to discover that I am just pretengind too much silence for a product of its era.
I hope that people answering at McIntosh could understand this kind of issue and give good indications on how to solve.
jwags818, you're so kind in offering you help, but I don't want to be a bother.
If they can't ship to Italy due to an agreement with the local distributor, I will let you know.
What is the best way to call them? I'd just have to go with the phone numbers on the site?
My only fear is that this buzzing is kind of normal for Type 045416 trafos. Don't really want to buy a new one just to discover that I am just pretengind too much silence for a product of its era.
I hope that people answering at McIntosh could understand this kind of issue and give good indications on how to solve.
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In the meanwhile I've found the problem with the Left channel protection "Normal" lamp. The "Limit" lamp was burnt 😀
When the "Limit" lamp filament is missing, not even the "Normal" one lights up...
Looking at the schematic it looks clear: the "Limit" lamp acts as a pulldown resistor that keeps the base of Q208 BJT down, in order to keep it conduction. When the "Limit" lamp is missing, the R219 pulls up the base, switching off the "Normal" bulb. At limiter intervention, Q206 powers the "Limit" lamp and switches off the "Normal" one.
While I wait for an original replacement, I just put a compatible 12V bulb I have.
When the "Limit" lamp filament is missing, not even the "Normal" one lights up...
Looking at the schematic it looks clear: the "Limit" lamp acts as a pulldown resistor that keeps the base of Q208 BJT down, in order to keep it conduction. When the "Limit" lamp is missing, the R219 pulls up the base, switching off the "Normal" bulb. At limiter intervention, Q206 powers the "Limit" lamp and switches off the "Normal" one.
While I wait for an original replacement, I just put a compatible 12V bulb I have.
My experience with E-core transformers is that they eschew quite a bit of magnetic radiation. I'd go with the toroid. This did wonders for killing noise in a tube amp I built.
I am in contact with them and will pass along the info as soon as I hear back. Yes they will sell parts direct as they do their own service and do not rely entirely on dealers. They are almost 100% vertically integrated. They build everything they can themselves. machining, sheet metal, glass work silkscreening etc...
I am dealing with the lady that i worked with before when she helped me get my amp refurbished. The price was very much lower than I was expecting.
And any Mcintosh transformer will not buzz normally. They are one of the few companies that will work on and warranty the work on an amp that is 50 years old. Quite amazing actually..
I am dealing with the lady that i worked with before when she helped me get my amp refurbished. The price was very much lower than I was expecting.
And any Mcintosh transformer will not buzz normally. They are one of the few companies that will work on and warranty the work on an amp that is 50 years old. Quite amazing actually..
If you like I will pass off to you as soon as I hear back. Her name is Sharon Butts 1-800-538-6576 ext 444. Just tell her you are continuing up on the request started by Jeff Wagner. I do not own any McIntosh gear anymore but as far as a company goes I have never had better customer service. And if you replace the transformer with one of theirs your amps value will be much higher should you ever trade it in or sell it. I have no connection to them at all, just like the way they do business.