Question on Twin conversion to non HRM

[Tonegeek]

I took the plunge and started stripping my early 70's Twin in prep for a non HRM build. My original plan was to only reuse the trannies, choke, pilot light and chassis. But, as I rip into it i am wondering...

1) Should I reuse the tube sockets?
2) Should I reuse the old, dark brown tone caps?
3) Till now, I have only built the precision PS, but should I build the old style (non-totem) one instead? I will have to add extra filtering regardless for the built in dlator.

[David Root]

Sure, re-use tube sockets, clean them first and retension the pins if necessary. Re-use tube bear clips, switches if they worked OK in the original, re-use the fuse holder, just about anything that is not a carbon comp resistor or an electrolytic PS cap. Don't reuse the boards. The brown coupling caps are a matter of taste, in a Dumble you're going to want 6PS orange drops I think.

I would not use any self tapping chassis screws even if they are original. Drill 'em out and use #6 machine screws with a KEPS nut.

After all this stuff fits without drilling the chassis. You'll be doing that anyway so why not minimize it, especially in a steel chassis.

Personally I would not re-use the HV power supply or the bias supply as modern hexfred soft recovery diodes are soooo much better.

I did the same thing with a'67 Bassman except I moved everything into a BFPR chassis, so I had mucho drilling to do anyway. Worked out fine. Had to replace the slide switches with NOS, the originals were done, sticking all the time. Apex Jr has those that fit BF Fenders.

[jelle]

Add point 3:

The old school PS works great.

Also, those brown caps....you may like them, try it! I would try it and a good sounding amp, is a good sounding amp. Maybe use a 6PS for CL2 out.

[kleinm]

1) They'd be great, just clean the socket and retension as mentioned.

2) Personally, I wouldn't. Not because I don't think they'd sound good...but because they'd be better suited for a different project. Hell, you might even be able to pull the "turd" caps and sell them on eBay to pay for the conversion!

3) I like the older power supply quite a lot. I think you'd be equally happy with either.

[David Root]

I forgot the jacks and pots. Clean the pots with the Caig pot cleaner formula, check that the shorting jacks work properly.

[Tonegeek]

I forgot the jacks and pots. Clean the pots with the Caig pot cleaner formula, check that the shorting jacks work properly.

I was going to go with cliff jacks because I have a ground scheme that works using those and don't want to mess with the formula. Problem is, I bet they won't fit. Have to research that. I could reuses some of the pots. Some of this is dependent on how nice I want this thing to look and how reliable I want it to be. Was thinking it might just be a testbed/personal use only project in which case I would resuse much more of it, but I kind of also want to see how 'professional' I can make it. Of course that will drive the cost up.

[Tonegeek]

Add point 3:

The old school PS works great.

Also, those brown caps....you may like them, try it! I would try it and a good sounding amp, is a good sounding amp. Maybe use a 6PS for CL2 out.

I think I will give the old school PS a try. I would like to use the doghouse for the caps, but if they don't fit, figure something out. I may need some help on the dropping resistors needed for the d'lator. i only have it worked out using Marshall iron and doubt that will work on this project as the voltage is a bit lower. I usually just tap right after the choke for the d'lator supply using 2 caps and 2 resistors. I believe the recovery side of the tube is supplied first (~220v at the plate), then the follower (~260 at the plate).

I will order all the ps caps but keep the option to reuse the turd caps.

[Tonegeek]

Personally I would not re-use the HV power supply or the bias supply as modern hexfred soft recovery diodes are soooo much better.

I think I have 4 U4007 (I am guessing at the PN - got em from Mouser). Will 4 of these work instead of 6 1N4007?