BF Champ/JCM800 build

[M Fowler]

I had a BF Champ chassis from rjguitars and some Trainwreck transformers sitting around.

Chassis www.rjguitars.net
PT Pacific 280-0-280 300mA
OT Heyboer HTS-8093-1 with 4k3 primary 4/8/16
no choke
Solid State recto
JCM800 2204 50w circuit modified to single input jack.
Shorten broke Ceriatone Express face plate.

Got to be messy when I found out I had installed a bad OT

This little thing kicks butt but needs a Champ headcab

Mark

[xtian]

Mark, the title of this post, "BF Champ/JCM800 build," is priceless. It's like fitting a big block Chevy engine in an Smart Car. Awesome. Can't wait to see and hear the finished product.

[M Fowler]

I had the little puppy wide open today neighbors at work!

Man I love the tone from this amp and that surprises me because I was sure I would need higher plate voltage to achieve a good Marshall tone. I am using JJ EL34's and may try a set of 6V6's.

I'm going to add an effects loop to get a quality reverb going. The Boss reverb through the input gets too wild when you crank it up.

Mark

[Reeltarded]

Lol ya nutball!

Reminds me of my drummers Austin Sprite with a Ford 302 in it.

[Jana]

Mark,
Some of the best sounding 50 watt Marshalls I have had experience with had a B+ voltage of around 380.

[M Fowler]

Lol ya nutball!

Yes I'm just not happy unless I'm up to no good

Jana I didn't know that about low voltage Marshalls but glad to hear that. Now I can build some more.

I don't miss the hi/low input either as I always used the high gain jack.

[Reeltarded]

Oh yeah, about that voltage.. Umm 450 @ 120vac in that I kill off too what is umm.. sometimes 300-320. Less is more (awesome)...

[Colossal]

Mark,
Some of the best sounding 50 watt Marshalls I have had experience with had a B+ voltage of around 380.

Jana,

Do you know which models used lower B+ on the plates? What were the OT primaries in these amps?

Thanks!

[Jana]

It was the 4 holers with the upright PT that came just after the ones with the lay down transformers. I don't know the exact years--I have never been good at keeping track of dates. There were also some 2204 models with the vertical input jacks that, for the first few years, had the lower B+ PT.

I had a 1989 organ model with the small top enclosure that had the lower B+. That amp really sounded sweet and I played a lot of gigs with it. That was back in the day when they were a dime a dozen (almost) and it wasn't a blasphemy to mod the heck out of them--which I did and eventually scrapped it. Oh, if I could only turn back the clock and undo my actions and have that amp back in the condition when I got it--mustard caps, Daly cans, etc. Oh well, I learned a lot from that amp.

The OT was 3.4K or thereabouts. Marstran has the transformers that duplicate the PT and OT--it is the 784-139 for the OT and the 1202-164 for the PT.

[Colossal]

Thanks for the details! Good to know. I'll do some digging on those part numbers.

[M Fowler]

Here is a layout I modified to show wiring the single jack input.

Mark