MC275 Power Transformer Buzz
- Thread starter neskor
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Pio1980
AK Member
Maybe, but is expect blown fuses with an overload that significant.
Nonetheless, a recap of the power supply wouldn't be wasted. If the tubular caps re all red letter Sprague 160P, they are likely still ok.
Bill Ferris
Lunatic Member
I MHO/E, That amplifier needs to be carefully gone through and at minimum, all the electrolytic/color band striped capacitors replaced before it`s used anymore, or there is a very good chance of very expensive, or ir-repairable damage will happen to it !
If a un-properly restored Mc tube amp that`s tar embedded and encased power transformer can be heard humming, well that`s not a good sign at all, and most likely bodes abnormal current drawing stress through it !!
Continue to operate a un-restored very valued classic Mc tube amp at your own risk !
Ciao
If a un-properly restored Mc tube amp that`s tar embedded and encased power transformer can be heard humming, well that`s not a good sign at all, and most likely bodes abnormal current drawing stress through it !!
Continue to operate a un-restored very valued classic Mc tube amp at your own risk !
Ciao
clinic-audio
all on YAMAHA untill 1990
Hello
There is a simple test to do : disconnect the secondaries of this power transformer and listen if it is making noise with no load condition .
Before to reconnect it use an amp-meter to check the power consuption of the unit
You will see immediately if there is something wrong
In my point of view , there is something wrong and using it this way is dangerous and a great risk
There is a simple test to do : disconnect the secondaries of this power transformer and listen if it is making noise with no load condition .
Before to reconnect it use an amp-meter to check the power consuption of the unit
You will see immediately if there is something wrong
In my point of view , there is something wrong and using it this way is dangerous and a great risk
Bill Ferris
Lunatic Member
Do you happen to know your average line voltage, as sometimes the voltage runs a little on the high side ?
And if so maybe, if it`s not already been changed over to the 126 volt primary optional tap from the factory`s default of 117 volts, that might be helpful to lower the hum a little more, along with checking the physical tightness of all the power transformers under the chassis bolts & any of the transformer`s can cover screws..
Just some suggestions, neskor
And if so maybe, if it`s not already been changed over to the 126 volt primary optional tap from the factory`s default of 117 volts, that might be helpful to lower the hum a little more, along with checking the physical tightness of all the power transformers under the chassis bolts & any of the transformer`s can cover screws..
Just some suggestions, neskor
clinic-audio
all on YAMAHA untill 1990
Today I tried to power transformer with disconnected secondaries and still buzz is there
Hum , not really a good news
Only one thing to do, replace the power transformer by a new one !
A good power transformer don't make any noise
Where are you located ?
I'm Europe, that will be a problem to find Power Transformer here.
Tried to contact AudoClassic but they don't have it on the stock.
If you maybe know other place to find please let me know.
Thanks.
The power transformer is potted in a tar material into the can, which should keep it quiet.
Is there any of that tar under the transformer indicating it has run too hot?
If voltages are all good, and the transformer isn't running hot, I'd consider removing it, inverting it, and re-melting the potting material with the hope that it will fill any void in the transformer potting and damp the vibration/buzz.
Is there any of that tar under the transformer indicating it has run too hot?
If voltages are all good, and the transformer isn't running hot, I'd consider removing it, inverting it, and re-melting the potting material with the hope that it will fill any void in the transformer potting and damp the vibration/buzz.
Bill Ferris
Lunatic Member
Also the OP indicated he resides in Europe, so how is the 275 powered, being Europe`s voltages are in the 220 volt range ?
Is his a 275 with the factory export factory power transformer, or is he powering a domestic one with a 220 to 120 voltage dropping external transformer, and if so what is it`s wattage capacity rating..
He did indicate the use of a variac type variable AC mains voltage device used in his no secondary connected testing in post #12..
More information from him is needed, to help guide/trouble shoot effectively, IMHO/E.
Is his a 275 with the factory export factory power transformer, or is he powering a domestic one with a 220 to 120 voltage dropping external transformer, and if so what is it`s wattage capacity rating..
He did indicate the use of a variac type variable AC mains voltage device used in his no secondary connected testing in post #12..
More information from him is needed, to help guide/trouble shoot effectively, IMHO/E.
My MC275 is for USA market, so 120V Power transformer.
I'm using step down transformer to drop line voltage from 230V to 120V.
I also tried to power without stepdown transformer with variac, dialing to 120V, but the problem remains.
Is there any chance to buzz because 50Hz is main line instead of 60Hz?
I'm using step down transformer to drop line voltage from 230V to 120V.
I also tried to power without stepdown transformer with variac, dialing to 120V, but the problem remains.
Is there any chance to buzz because 50Hz is main line instead of 60Hz?
clinic-audio
all on YAMAHA untill 1990
no !
clinic-audio
all on YAMAHA untill 1990
your power transformer need to be replaced no other way
Bill Ferris
Lunatic Member
The 50 Hz line frequency could be a deciding factor..
While you were in the amp with the bottom cover off, did you happen to notice any globs or tar where the wires from the power transformer come through either of the chassis` openings ?
EDIT: Never mind, If Patrice says the transformer is bad and I won`t doubt his assessment !
