Tube Amp Archive

Thanks for replies. It‘s a somehow complicated switching heater and relay supply for 12.6 Volts DC, no schematics or instructions available. It had some issues with the relay supply and a shorted flyback diode, but now I set the trimpot for 11.98 Volts DC and the Amp is working again.

Hi, I‘m working on a Bogner Shiva 20th Anniv. and need Informations on the setting of the small orange trimpot on the separate heater pcb. There‘s no schematic of the Shiva‘s power supply available. Thanks for Informations, hints and help
Zouto

I use NOS 6P14P-EBs in several Vintage AC30s for a warm and chimey sound and great reliability. It‘s important to select good quartets.

Yeah, this is the right link to the output transformer
https://www.hammfg.com/files/parts/pdf/1750WA.pdf

The amp rebuild has taken a bit on an unpleasant turn with the discovery that the output transformer is not the original output transformer. The original output transformer has the number 021667 and it's obvious that it was larger than the current transformer which is a Schumaker 022889, which was ...

You might want to lower the wiper resistor to ~5K to give more range. It gives a minimum bias voltage when the pot is turned all the way up. It'll give you ~ 20volts of adjustment. i.e. your currently -14v fixed Installed -6v to -26v adjustable. I just tried this in my trusty .22, just did not work...