Help! Metro 12000 Series hum

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ppyyff
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Help! Metro 12000 Series hum

Post by ppyyff » Fri Jul 22, 2016 11:16 am

Hi everyone.

I'm from China. I built a Metro 12000 Series 100W head with all the transformers from Heyboer and parts from valvestorm. It sounds great!

However, there's a hum from the speaker which is annoying me.

1. The hum is not loud, but I can hear it if the room is quiet.
2. I can hear the hum when I just turn on the amp and do not turn on the standby switch.
3. I pull out all the preaamp tubes and power tubes. Hum is still there.
4. Then I disconnect two 3.15v heater wires. Hum is still there.
5. I put a metal sheet between PT and OT, Hum is still there.

Does anyone know when the hum comes from? wrong OT orientation? heater? or anything else?

How can I get rid of the hum?

Thank you very much!

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VelvetGeorge
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Re: Help! Metro 12000 Series hum

Post by VelvetGeorge » Mon Jul 25, 2016 11:47 am

Is the hum present in standby? This is normal and is due to transformer orientation. You can rotate the OT to resolve.
If it's still there when you flip the standby ON, then its something else. The high voltage applied to the OT should swamp out the induce hum.

george
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