Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Frank on February 28, 2019, 06:31:05 pm

Title: Help with older Hoffman Plexi50 wiring
Post by: Frank on February 28, 2019, 06:31:05 pm

Hi. I'm in a holding pattern, trying to figure out how an older Hoffman Plexi50 power section was wired,


The board is labeled "Plexi-50 Board 1/29/96".
It has already been pulled out of the chassis. (Argh)
The Power, Standby, and Fuses sections appear to be different from the latest layout graphics found on-line.
I can either find somebody who knows how this was wired, with access to older layouts, or...
I can pull everything off and start over. If so, can anyone point me to a  layout showing the lamp, Mains, Standby, Fuses, AC input>?


I appreciate any help you can provide. Thanks.

Title: Re: Help with older Hoffman Plexi50 wiring
Post by: sluckey on February 28, 2019, 06:47:04 pm

Maybe this...

(https://el34world.com/Hoffman/images/Plexi50Old.gif)

Title: Re: Help with older Hoffman Plexi50 wiring
Post by: Frank on February 28, 2019, 06:58:47 pm

This might just be right! Cursory review looks similar...

Title: Re: Help with older Hoffman Plexi50 wiring
Post by: Frank on February 28, 2019, 07:08:57 pm

Except for the Mains switch, this looks right. It might be right for the Mains, but it doesn't look similar. Do you have more detail how the Mains was wired, and tied in through the Indicator?
Thanks for the help so far! Seriously.

Title: Re: Help with older Hoffman Plexi50 wiring
Post by: sluckey on February 28, 2019, 07:26:59 pm

There is no right or wrong. If Hoffman sold 1000 of these boards there will be at least 900 different variations on the PT primary wiring. Just wire it so it works.