Peavey Bandit 112 (USA) to custom job...but what?

So last January I picked up this nice Peavey Bandit 112 USA Sheffield combo, worked ok except for some of the pots were busted and the normal input jack was looser than a !censored!
It also came with 2 guitars, an 80's strat copy with no strings and a cool 60's 4 pickup Japanese curiosity, the guy was happy with £20 as he didn't play guitar and didn't know how to fix them.

It's all stripped down and waiting to be transformed into a nice custom job tube amp.

The chassis is 9 1/2" x 21" x 1 7/8" nice n roomy but the aluminium sheet is quite thin.

Speaker works nice.

I tested the long spring line reverb tank (ss higher impedance type) with a tube drive circuit similar to a '63 fender reverb unit and sounds great.

The cab is solid and heavy, I'd like to change the speaker grill to a 60's fender look.

I've unwound the power transformer and can reuse the laminations/end bells and rewind it to custom values.

Tube I have in the octal drawer:
4 x EL34
8 x EL84
2 x 6L6GC
11 x 6V6
6 x EL36 (Russian type TV line drivers, these can put out some serious power eg 60W form a pair - top cap anodes too)

The OT will depend on whatever power tubes are used.

But what to build, a Deluxe Reverb inspired comes to mind.

What do you think?




Doug.

 

Here's the 1960's Japanese guitar I got for free with the £20 amp.

 

All ideas welcome

I do have plenty of those Russian 6V6 to use up, could put 4 in there and have a bias switch to enable to run on 2 or 4 tubes, would need to pull 2 tubes (one from each side) out.

I was also wondering what to do with the front panel, I could keep it original and have 2 channels, I also can use the reverb tank and keep the reverb control. I kept the relay components, need to test them 1st, so could add channel/reverb switching.

I don't mind going full custom hot rod.

Doug.

 

I did a setup on the Tiesco, frets were ok, I put a shim in the neck pocket to give it a slight break angle. The main issue is the bridge, it was at right angles to the strings with no way to set intonation, I set it at slight angle to get it closer. Lots of contact cleaner on the pots and switches.
It needed a good clean too, bit of rust too but it is quite old.

 

It's nice to have so much space inside, will be better once I move the power cord entry point and panel mount fuse holder to the rear panel, just trying some layouts.

 

Here's a different way to arrange the chassis, any issues with it?

The 4 octals don't have to all be populated, could just run with a pair, add bias adjust pot and switches to enable running with a choice of 6V6, EL84 (extra 9pin bases wired to each octal), EL34 or 6L6GC and use the 4 Ohm OT tap run into an 8 Ohm speaker trick.

The transformers are just there to see how they would fit, the PT in the photo only has a 3A heater secondary, the HT is 260V @ 350mA and the bias 25V @ 250mA (would need a voltage doubler)
I plan to wind a custom PT with added taps for a range of final DC B of, eg 150,300 and 400V

Doug

 

Thanks for the info, I don't have a schematic yet so I thought I would go with a 'evolving' build, I expect a lot of changes along the way and some suggestions from the guys here.

The tag strip allows a lot of ideas to be incorporated along the way and it will end up more like a point to point build.

Good call on the choke, you reminded me to have a look through my stash of bits and found a brand new boxed Hammond choke I planned to build a deluxe reverb with, also found a Hammond reverb transformer too.

I'm planning to incorporate the '63 Fender reverb unit circuit in the combo and maybe try to have it controlled by a foot switch and relay. I have had some good results with a transformer-less tube reverb driver in my 6V6 SE champesque amp, I could build both types and compare them. I have low and high impedance tanks.

Doug

 

My current planning stage ideas (maybe too much crazy stuff going on!):

I have a JCA22H (Soldano design, Chinese made) head 4 x 12AX7 and 2 x EL84, it has a tube buffered effects loop, I'd lift most of the design from it.

2 channels, clean and overdrive.
Clean channel would be V1a/V1b with a gain, TMB and master vol, overdrive channel would get the same with an extra triode stage. Foot switch/relay to swap between channels.

Reverb via send/return buffer, foot switch/relay to bypass.

B+ voltage selection via 3 way rotary switch, Low 100-150v (depends on the right brown-out type sound) 300v for the 6V6/EL84 and 400v for the EL34 and 6L6GC.

Bias adjust knob to set bias depending on tube and how hot you like 'em.

Output impedance switch, eg 4/8/16, the current speaker is 8 Ohms, if I run with 4 tubes then select 8, if I run with 2 tubes select 4 into the 8 Ohm load, 16 if I run to an external speaker.


Doug

 

So, today the donor power transformer parts from the Peavey SS amp was mutated (lams and end bells only) into a tube amp PT

I entered the size of the core (width of E plate tongue x height of lams stack) into my tube amp power transformer program and then added the windings I required (for taps, leave the current required blank)
I've gone with an HT with multiple taps 0-120-220-360v @ 160mA, a bias supply of 50v @ 10mA and 2 x 6.3v at 3040mA (enough for 4 x EL84) and 3000mA (I entered these at 6.9v to account for the voltage drop under load). I plan to add a voltage drop feature to my app to calculate this based on the length of wire.



It's wound and assembled.



5lb or 2.3kg

I measured the ac voltages with no load on the HT and bias, today my mains voltage was a wee bit lower at 235v (should be 240v)

0-120-218-359 and 48.5v

So close enough, might have been spot on if the mains was at the usual 240v.

On the heaters side, I measured the ac voltages without a load and with the load of a single EL34 drawing 1500mA (as per data sheet)
1) 6.87v no load and 6.3v under load
2) 6.86v no load and 6.2v under load

So all good

Doug.

 

http://primarywindings.com/ do a nice 10W SE output transformer, only £30 ex p&p.