Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: 451stroker on March 16, 2019, 07:47:54 am

Title: Plexi Retrofit Into Combo
Post by: 451stroker on March 16, 2019, 07:47:54 am

I bought Steve's 6v6 Plexi with the intention of transferring the components into an old Marshall SS combo amp chassis. Steve and Dave have been extremely helpful with their advice, so I'm starting this thread to document the build (or retrofit).

I have to say up front that I'm more of a guitar player, not really a builder, and have very limited knowledge of tube amps and electronics in general. So, I'll probably be posting some questions that make your eyes roll back. But, thank you in advance to all of you who have already helped me or may help me in the future.

As for the new chassis, I didn't take advantage of the additional space because I wanted to maintain the component layout of the original chassis. This is strictly so I could maintain as much of the current wiring as possible, since the less of Steve's amp I take apart, the more likely I am to be successful in the end.

Here's the chassis that I drilled so far:

Title: Re: Plexi Retrofit Into Combo
Post by: 451stroker on March 16, 2019, 07:57:43 am

One of the things I'm looking to change with the amp is to convert it from a tube to a SS rectifier. I don't want to use one of those plug in types because I want to avoid putting another hole in the chassis.  The rectifier below is the same spec that comes in a 50 watt JMP Marshall. Would this work for my 6v6 Plexi build?

The specs are 1000V and 25 Amps.

Title: Re: Plexi Retrofit Into Combo
Post by: sluckey on March 16, 2019, 08:19:52 am

yes

Title: Re: Plexi Retrofit Into Combo
Post by: shooter on March 16, 2019, 10:06:24 am

did you play it 1st  :icon_biggrin:

Title: Re: Plexi Retrofit Into Combo
Post by: 451stroker on March 16, 2019, 12:05:08 pm

Quote from: shooter on March 16, 2019, 10:06:24 am

did you play it 1st  :icon_biggrin:

Hey Dave,

Yeah, I like it. I just want to change the rectifier and add an FX loop.

Title: Re: Plexi Retrofit Into Combo
Post by: sluckey on March 16, 2019, 02:25:50 pm

Before breaking down the working amp and before committing to ss rectifier, I would put a ss rectifier in the working amp and see how high the B+ goes. It may also need a bit of bias tweaking. May be just what you want. Or maybe not. But at least you will know with just a little time investment.

Those 6V6s in the amp are 1960s NOS milspec but they may not like higher B+. JJs should be fine with the higher voltage.

Oh yeah, about that bridge rectifier... It's only being used as a 2 diode conventional rectifier. DO NOT CONNECT THE NEGATIVE LUG TO ANYTHING!