Hoffman Amplifiers Tube Amplifier Forum
Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: plexi50 on June 22, 2010, 11:08:24 am
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I have had a few Subway blues in this month for the hum problem they are known to have
I looked at the speaker out jack and touched the metal case of the speaker input plug and all noise went away
I looked further and noticed the common wire coming from the OT secondary was soldered to the cliff jack but there was no ground reference to it other than it making contact with the sleeve of the speaker input plug
I installed a gound lug to chassis and wire from there to the common wire on the cliff jack
Turned on the amp and it is dead church mouse quiet. Sounds like an amplifier should
I did not bother to look further down the line on the rear panel to see if there was a ground for the board the outputs were mounted on / My mistake as i want to be thorough. In any case this fixed the Subway Blues and Subway Rocket Reverb for me
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Thanks for the tip!
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I was going to keep it to myself but this is where i learned from all of you so what the heck. Have to give back as well
I was really surprised that there is no mention of this any where on the internet. It's plain as day and the amp is SILENT
The OT common ground is floating. There may be more to this but from what i see it's the hum cure plain and simple
There is another model though that had those Mojo modules on the board. That one may need the .68 cap near one of the moduels