Hammond organ amp conversion to guitar amp.

[Philoffline]

Hey, Victor, I've got exactly the same amp, and more or less the same intentions. I'm looking at AC-15, Lightning, and Spitfire schematics and thinking that I'll try out each circuit, or variations anyway, in this box. Both to see what I like and to learn how these things work - I'm pretty new to EL84s.

IMO it's a nicer setup than the more well-known AO-35. This one's got room for 3 preamp tubes and a built-in eyelet board. As for the voltage, I figure it's easier to start with too much and bleed some off than the other way around.

Please post up if you learn or do anything cool with it!

[mmmoser]

I have used these amps as the basis for several conversions. I build one out as a Fender Tweed Bandmaster years ago. I sounded great.
More recently I built one for a customer that was a two channel amp- one was an EF86 based Vox style and the other a Marshall based circuit. I recall using the Trinity version of this amp as a starting point. The customer also wanted a pentode/triode switch and a few other goodies. It all fit but its tight. I did have to use zeners to drop some voltage. Here are a few shots

[M Fowler]

Good looking conversion, Tweed Bandmaster, nice.

Mark

[Philoffline]

Very nice. I'll be pleased if I can get just one channel looking that good.

Same power section for both front ends? It looks like something on the output tubes goes through a switch, but I'd guess that's the pentode/triode mod. It also looks like there's no filter choke used?

[DustyBadlands]

The Hammond conversion ...Thanks for the useful information! I'll post some voltage readings when I get a chance.
I'm real happy with the way the amp sounds. No hum or buzz with a Les Paul. I have not tried single coils yet. Here are some pics.

B+ is 390V....
GZ34 Rectifier
EL84's are Russian 6n14n-EB

[DustyBadlands]

Just an FYI...as Mr. Fowler suggested the 18watt.com forum has a lot of information on the Hammond model H-AO-43 conversion.Thanks.

[Structo]

Nice conversion although I hate seeing that wire nut in there.

Perhaps a solder joint and heat shrink tubing is in order there?

[DustyBadlands]

Point taken...I'm on it.

[M Fowler]

Awe Hammonds all suck big time.