Marshall VS100 Repurpose

[TIMBO]

Hi guys, I've gathered some bits to kick this one off.



So I'll share the HT between the 64v winding to power the output and phase inverter.
The 0-240v for the preamp
The 12v for a relay
An extra 12v transformer for the heaters
The BASSMAN MINI board can be modified for several 5F6a type circuits, so I'm going to do a Bogner style STC circuit.

[Stuff4bikes]

I have an absolute mint vs65 on the outside and just a mess on the Inside. Thinking about gutting it for a rebuild also.

[uki]

Looks interesting!! Is the chassis from another cab?

[Stuff4bikes]

Looks interesting!! Is the chassis from another cab?

I am not the OP but that looks  like the original chassis in mine.

[TIMBO]

Original chassis



Hi guys, PSU built with Supply to elevate heaters and Bias for the power valves.

[Stuff4bikes]

I am new to amp building, can you explain that power supply...are you going supply power the HT with a 64v transformer?

[TIMBO]

Hey mate, It's called a quadrupler, so it will multiply the input voltage by 4X and also rectifies it to DC which is then multiplied by 1.4.
We should be looking at an Approx. voltage of
64x4x1.4=358V
A bit less once loaded.

[Stuff4bikes]

Will you be using the original Marshall transformer and a seperate heater transformer?

[TIMBO]

Yes

[mwelch55]

I'll be interested to see how that turns out.  I wouldn't think you would be able to deliver enough current to supply 2 5881s.

Mike

[PRR]

What was it doing stock? Like 90V at 2 or 3 Amps? De-quadrupled would be 500mA. More than a couple bottles are liable to suck at 350V.

[TIMBO]

Hey PRR, Got a pair of 5881 for the output duties, or can do a pair of 6V6.

[TIMBO]

Hi guys,I thought I'd a bit of experimenting with the HT voltages.
My first thought was to just use the 32-0-32 (0-64) tap as is and connecting the quadrupler gave me about 345v unloaded.
This would probably produce about 20w output with a pair of 5881 valves
The PT has a 15v tap (12v heaters approx 250mA)
I wired this in series with the 64v tap and the voltage quadrupler hit the 440v unloaded.
I'm thinking this will should give me about 30w output.

[TIMBO]

Board populated and ready to be wired in

[TIMBO]

Board just about wired in


I'm thinking of adding the SLO depth control.....

[uki]

The board have a good looking !!!

[TIMBO]

Hi guys, Wiring is all done and has fired up well.
I have a bias setting sheet for 6L6s, will this apply to 5881 valves?
At the moment I have 350v on the plates and 58mAs on the cathodes

[shooter]

if the 58mA is per tube, that might be a tad hot.  I get ~20W/tube at 58mA (including G2)
my understanding 5881 is closer to 6V6 power-wise, but I didn't look anything up

[TIMBO]

Thanks shooter.
Wiring is done.
Depth mod added
Fired up well  :thumbup:







I have set up the "BOOST" to be foot switchable, being a bit lazy I was not going to use a relay to do the switching.
As there is no signal or power in that part of the circuit is a relay necessary???

[southboundsuarez]

Cool build
Never considered voltage doubler circuits in guitar amp build. I had previously learned about them in linear RF amplifier builds.
Never noticed it in guitar amps but surely with cost constraints there certainly must be guitar amps that exist with this type of power supplies.
Nice work. Good luck with the relayless foot switch. K.I.S.S. is good engineering!

[TIMBO]

Hi guys, I have done this circuit several times and it never fail to get the multiple thumbs up from my stunt guitarist.
The "PLEXI" channel is clean at lower levels a can grow some nuts when cranked.
The blue channel has got it all.
Set your guitar volume at half and your sound cleans up nice, articulate and smooth.
Crank your volume and your sound explodes (in a good way)
Engage the boost and you go to the next level without getting mashed out.
The structure goes from compressed and tight to loose and gainy.
Stock speaker sounds great.
Faceplate on the way and a sound clip in the works....

[TIMBO]

Hi guys, Another amp I need to finish
I'm slowly running out of valves, so digging through stash and found a nice pair of 7591A's
Rewired the sockets and fired up, alls good

7591a.pdf (r-type.org)
Data sheets has bias set at -16v at approx 370v on the plates
I'll take it that is where they should be set at.
Sounds great....
Never got around to getting the face plate make, so that is on order.

[sluckey]

I have a 7591 amp. Bias is -25V and plates are 470V.

http://sluckeyamps.com/hammond_2/AO-63.pdf

[TIMBO]

Hey sluckey, I'm pretty sure that's why I have a pair of 7591's as I had a AO-63 chassis.
I can only go by the data sheet as my cheat sheet doesn't have the settings for that valve.
As a side note, does that cheat sheet still exist on the forum?

[TIMBO]

Hey sluckey, I checked out your AO-63 and noticed that pins 8 and 4 are connected externally (on the socket pins)
Is this required????

[sluckey]

I don't know what cheat sheet you are referring to.

Pins 4 and 8 are internally connected so it doesn't matter. Hammond put the external jumper on the socket for convenience of wiring the screens (just a guess).

[TIMBO]

Thanks mate.

[TIMBO]

DONE!