Transformer buzz?
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karsavuran
Active Member
I do not know the answer but there is no buzz on my MC30s and MC225.
Good. You had them serviced before, right?
karsavuran
Active Member
for the mc30s yes, they was fully original when I got them. I tested before servicing and there was no buzz at that time as well.
I got the mc225 as not working, seller described as the internal fuse blows and before that there is a hum/buzz from the transformer for a few seconds.
As far as I see it was fully original too. I replaced a shorted bumblebee and it works now. I did not do anything further on it but also I am not using it. I only tested it for a few minutes.
I have MC30, too, but no hum or buzz. The only time I heard a loud hum was when one of the big silver multi-can cap on the chassis had a problem. After it was serviced, it's all good,now.
Mechanical buzz?
Does the transformer get blistering hot after it's been in use for a while? Are there any tubes red-plating? Is the amplifier operating normally? It is odd for a potted transformer to mechanically produce any audible buzz.
I hear a slightly audible buzz from the transformers (MC225, original) when turned on. With about 12 hours on, the temperature of the power transformer is 117F.
Temp seems reasonable.
I am thinking of recapping the old bumblebee caps and power supply caps in the near future...
Thanks for your feedback. After 12 hrs of running, around 117F, and no red plating at all.
As you know know, our forum gurus' standard advice on vintage McIntosh gear is have them restored or rebuilt, regardless of their good performance, so I was thinking of going to that route.
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First, @w3jn IS one of “our forum gurus”, one of the best.
As far as the restored or rebuilt, it is good advice and I agree that in general it is a good idea to go through the amplifier at this point, ensure that all parts including resistors, caps, tube sockets, thermistor, rectifiers, tubes, etc. are in good condition and within original (design) specs. Is it related to the noisy transformer or not? Hard to tell, usually there is some hum but it will increase with power draw so faulty components in some cases will increase the volume of that hum.
Try new tubes to see if it changes, but measuring voltages would be my first start on servicing to see if it has any problems and to establish a baseline.
As far as the restored or rebuilt, it is good advice and I agree that in general it is a good idea to go through the amplifier at this point, ensure that all parts including resistors, caps, tube sockets, thermistor, rectifiers, tubes, etc. are in good condition and within original (design) specs. Is it related to the noisy transformer or not? Hard to tell, usually there is some hum but it will increase with power draw so faulty components in some cases will increase the volume of that hum.
Try new tubes to see if it changes, but measuring voltages would be my first start on servicing to see if it has any problems and to establish a baseline.
I’m not necessarily saying it shouldn’t be gone through, just that the buzzing transformer (while annoying) isnt necessarily indicative of an electrical problem. 117 degrees on the transformer is fine. It absorbs radiated heat from the tubes and creates some of its own.
Here is the recent thread where a member solved the issue by baking the transformer: https://audiokarma.org/forums/index...-transformer-vibration.1039753/#post-16632157
Here is the recent thread where a member solved the issue by baking the transformer: https://audiokarma.org/forums/index...-transformer-vibration.1039753/#post-16632157
I wouldn't describe mine as a 'noisy' transformer. It's just a 'slightly audible' buzz from the transformers. Probably 2~3 out of 10. It doesn't increase or decrease with the volume.
The buzzing is not that annoying as it's slightly audible when I put my ear close to the amp. I don't hear it while listening to music or FM radio. But as you mentioned, this is indicative of an electrical problem as the transformer is buzzing, even slightly. I'm going to have it checked and fixed, with recaps, etc, by Audio Classics sooner or later.
Here is a link to the video of this buzz on youtube I just uploaded for your reference. If you put your smartphone to your ear, you might be able to hear it more closely.
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Not that there’s a clear definition of “buzz” vs “hum”, but I feel that there is hum, a softer sound that a transformer normally makes, and a sharper buzz, which would indicate an abnormal load or loose windings. Hum is normal and will increase with load (not necessarily volume control settings), but an abnormal load like leaky filter caps or other leaks that would also result in a hotter transformer.
It sounds normal from the video, and 117* is about what I’ve measured on my MC240 after a complete service, but of course there is no volume reference to tell you if it is louder than normal. I am not used to hearing the PT at all so maybe it is noisy?
The trip to AC will likely be a great way to have it ready for the next 50 years, and if the filter or doubler caps are leaky it’s a good time to have them replaced anyway I guess.
It sounds normal from the video, and 117* is about what I’ve measured on my MC240 after a complete service, but of course there is no volume reference to tell you if it is louder than normal. I am not used to hearing the PT at all so maybe it is noisy?
The trip to AC will likely be a great way to have it ready for the next 50 years, and if the filter or doubler caps are leaky it’s a good time to have them replaced anyway I guess.
I see. I don't hear anything like hum or buzz from the speakers. Thanks for your informative feedback. I'm not sure if the filter or double caps are leaky (I don't know how to check them anyway), but given its vintage status, I think it's time to have it overhauled sooner or later.