Hello all,
I got this amp working in January. And have since been tweaking the circuit as I chipped away at the head-shell and cabinet.
its not 100%, but I was itching to show you all some pictures as I'm super proud of this amp. and I figure its far along enough to show.
Specs / Mods
Vintage Transformers from an old 60's Fanon FMA65 Tube PA (Canadian)
OT rated for 60 watts.
PT didn't have center taps, so I used a bridge rectifier, and had to use a dropping resister to get the voltage to 470, down from 500.
Added a PPIMV
Removed Bright cap, tamed trebel
50k NFB Resistor, extra hair / Less bass
added Cathode 1uf bypass cap on V2a, for a touch of gain.
Increase trebled peak Cap C4 to .0022uf, tamed trebel
By far, the best mod, was increasing the Phase Inverter Fizz cap C18, I brought mine up to 150pf.
This amp was super brittle, but the few mods, and especially the fizz cap, just made this thing a bloody class act. Couldn't be happier.
Tubes
JJ - EL34'S
Phase Inverter: old Japan made - 12ax7a (Logo worn off)
Preamp Tubes: 7025A long black plates (logo worn off)
2 x 12 - 1969 Pre-rola Celestion Green backs, 75hz cones
2203 Build & Pics
Moderators: pompeiisneaks, Colossal
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pleasantbullet
- Posts: 65
- Joined: Tue Jun 05, 2012 6:19 pm
- Location: Ontario, Canada
2203 Build & Pics
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Re: 2203 Build & Pics
Pleasant: thats a great job!
I like how what you did standing up the trannies. I have a laydown trannie, and was wondering how i could get it to work without having to cut a big square in the chassis, now I know...very nice, do you have pictures of the insides?
I like how what you did standing up the trannies. I have a laydown trannie, and was wondering how i could get it to work without having to cut a big square in the chassis, now I know...very nice, do you have pictures of the insides?
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pleasantbullet
- Posts: 65
- Joined: Tue Jun 05, 2012 6:19 pm
- Location: Ontario, Canada
Re: 2203 Build & Pics
Thanks Joeboo,
I found these stand off type spacers from homedepot, that just happen to have the same thread and height of the old transformer mounting bolts, they are round tho, so they were hard to tighten.
It was definitely easier to work with on the inside, as space was limited in the hammond 16x8x2 chassis.
Here is a picture of the inside before the mods.
I found these stand off type spacers from homedepot, that just happen to have the same thread and height of the old transformer mounting bolts, they are round tho, so they were hard to tighten.
It was definitely easier to work with on the inside, as space was limited in the hammond 16x8x2 chassis.
Here is a picture of the inside before the mods.
You do not have the required permissions to view the files attached to this post.
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Reeltarded
- Posts: 9960
- Joined: Sat Feb 14, 2009 4:38 am
- Location: GA USA
Re: 2203 Build & Pics
Yeah, that's a peach! Really good work on the layout.
Signatures have a 255 character limit that I could abuse, but I am not Cecil B. DeMille.
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dcribbs1412
- Posts: 1377
- Joined: Wed Jun 11, 2008 6:56 pm
- Location: Arizona Desert
Re: 2203 Build & Pics
Congrats pleasantbulletpleasantbullet wrote: its not 100%, but I was itching to show you all some pictures as I'm super proud of this amp. and I figure its far along enough to show.
Tranny mounts look cool
69' Green backs gotta sound good
D
Re: 2203 Build & Pics
Nice looking build there. I like the board layout.
I'm betting it sounds great too.
A keeper !
I'm betting it sounds great too.
A keeper !
Why Aye Man