Hum in power amp chassis of Black Japanese built Ampeg SVT

[mark]

Hi

I have been battling away trying to rid my brother's SVT of a noticeable hum. The hum is purely in the power amp chassis. The hum appears to be coming from the anode of the 12DW7 valve.

The link below discusses the suggestions and things I've tried along with photo's.

Thanks for your time and patience.

Regards

Mark

http://https://ampgarage.com/forum/viewtopic.php?f=6&t=31414&hilit=Ampeg

[g1]

Can you post the appropriate schematic here?

[mark]

https://www.thetubestore.com/lib/the...-Schematic.pdf

This is the circuit that I'm using. Check out the Amp Garage link there is a lot of info there including what the earth path really looks like.

Regards

Mark

[g1]

For starters, that is not an 'official' Ampeg schematic, and those Piazza drawings sometimes contain errors.
Second, that is not the version of the amp referred to in that amp garage thread (loop jacks are directly grounded).
So find out which exact version of the amp you have, and find the proper and official ampeg schematic for it.
Post it here. (the attachments in the amp garage thread are not available to non-members, but maybe the correct schematic is shown in that thread?)

[mark]

The info is in the Amp Garage link, actual Ampeg circuit is there too in the first post. The circuit diagram doesn't show the layout of the power supply which is in the first post on Amp Garage. The link below takes you to the circuit diagram.

https://ampgarage.com/forum/download/file.php?id=51797

Regards

Mark

[g1]

Those links require membership at amp garage.