Total Butchery - can it be corrected

[heisthl]

Next Project. This is a freinds acquisition, I owe him for house watching/dogs sitting and wanted to build him an amp as a token of my appreciation - I thought it was a modded Princeton but it's not. It appears to be some 70 watt Fender that someone hacksawed down to fit a Princeton sized combo cab. It is the worst build I've ever seen and my first order of business is to remove every thing and start over. Note the Showman sized Fender iron. I'll be using Bassman iron, non-HRM and built-in FX loop.

[heisthl]

Rear View

[Normster]

That's one ugly mofo! About the only things that aren't completely destroyed are the transformers.

[Noel Grassy]

Oh that is lovely! Looks like you've gotcher work cut out for you. Best of luck

[heisthl]

Panels - Kinkos is only charging me 10 bucks for a sheet large enough for 6 individual panels. The finihed product is vinyl, self-stick and pre-trimmed. This gives you 2 extra tries on mounting them straight.

[jazzyjoepass]

Would be a good candidate for a pre-MESA Boogie production Princeton mod!!!

[heisthl]

This 4 x 11 is as big as I can cram in here without being too crowded. I put most of the FX loop on the board, as well as the PS and Bias.

EDIT - Removed outdated layout

[heisthl]

All gutted and ready to start building - here's a layout good enough to build from:

EDIT - remove out of date layout

[heisthl]

First power up tonight and very pleased. OD is very smooth with rich overtones and very singing tone without being too distorted. Still has a humbug and too high of voltages on the FX loop(D_Leator) tube that need correcting before I can get some clips.

[heisthl]

I ended up using Bandmaster/vibrolux type iron and I do notice a little less extreme low end on the clean sound (not a real complaint - It's still very full range sounding). This schematic (Hi Gains non-ODS) as drawn sounds amazing. The OD is much smoother and creamier (no rasp at all) than the previous MusicMan conversion. CL1 at 204v and CL2 at 208v. Changes from above layout: 1. added a separate cap can (40,20,20,20) all sections in parallel with the original 40uF to get rid of the 60Hz Hum. 2. Doubled the drop to 44K for B+2A by putting 2 22k series resistors in place of the single 22K (feeds plate of V3a) V3b plate now at 195v. 3. removed the 7805 from the relay P/S - it was not needed. 4. moved the 1K FB drain resistor and 1uF cap to the presence pot to get rid of a hum issue 5, set the OD trim to 40%. 5. Upped the bias resistor to 33K for more adjustment headroom. I'm almost afraid to do any more tweaking - it sounds too good. I'm out of country on a Blues Cruise for the next 8 days - I'll post the updated layout and some clips in a couple of weeks.

EDIT - 01/25/07 Changed above to reflect most recent changes.

[bnwitt]

Nice work. Looking forward to the final layout, some pics and a sound file. Enjoy the cruise.

[heisthl]

Probably the final schematic - unless I do something different!

[heisthl]

Layout Du Jour:

[heisthl]

Well I did a lot of experimenting and only made one "keeper" change tonight as far as layout/schematic goes - I updated the files above. I reduced the initial filter capacitance from 120uF to 80uF - this gave me maximum "sing". The NFB was best at the 8.2/1K values. I ran an additional shielded cable for the FX input grid. Next up is speaker selection I have a new RWBlues, an old Altec 12, a JBL D120 and various celestions to try. The speaker already in the amp is not too bad it looks like an Eminence but there are no numbers on it.

[heisthl]

Some Pix