Just for fun: Attempt at #40 schematic...

[heisthl]

I would think that a 1ohm bias resistor would be way more likely than the combination of Fixed and Cathode bias. This amp is early enough that just having a way to measure the combined bias via the 1 OHM resistor was atypical of guitar amps. That and the fact that that resistor would be brown from heat .

[ic-racer]

Here is a picture of what I was thinking. In the schematic the rheostat does not do much unless it is full on or full off. The overall effect is small, probably 3db. One thing that might be cool on the #40 build is to hook a 200r 10w resistor up to the ground switch and use the ground switch as a 1/2 power switch.

[Hotrod Ford]

IC racer,
to save you some extra work,
the smaller resistors you see in the pic of this amp is usually just the filament balance resistors,
Dr D normally used one from each tube socket , also most of these early ones had no 1R , and the caths were wired straight to ground behind the sockets just like a fender amp,
this one seems to have one single 1R though connected to both tubes the other filament resistor is most likely behind the bigger resistor on that pic

[ic-racer]

IC racer,
to save you some extra work,
the smaller resistors you see in the pic of this amp is usually just the filament balance resistors,
Dr D normally used one from each tube socket , also most of these early ones had no 1R , and the caths were wired straight to ground behind the sockets just like a fender amp,
this one seems to have one single 1R though connected to both tubes the other filament resistor is most likely behind the bigger resistor on that pic

TC

I'm pretty sure that 'hidden' filament resistor is on the V4 socket, between pins 7 and 1, with that little blue jumper wire to ground (from pin 1). Like I showed in the layout.

I enlarged this image and perhaps the power resistor does indicate 1R. I wish someone had pictures that were not jpeg compressed to death.

[heisthl]

The second fuzzy character is the mushroom shaped OHMS character. I used to have some resistors that looked just like this one.

[ic-racer]

The second fuzzy character is the mushroom shaped OHMS character. I used to have some resistors that looked just like this one.

I'll agree with that.

[Hotrod Ford]

I'm pretty sure that 'hidden' filament resistor is on the V4 socket, between pins 7 and 1, with that little blue jumper wire to ground (from pin 1). Like I showed in the layout.

I enlarged this image and perhaps the power resistor does indicate 1R. I wish someone had pictures that were not jpeg compressed to death.[/quote]


Ic-racer, those small ones on the socket are the grid resitors in this amp, fed by blue wire to one tube, brown to the other, those wires comes from pre amp board PI out
the big mushroom one ohm is clearly as I said a single common cath resistor in this very amp ,
this amp was probably specially built for both el34 and 6l6 use, hence the special set up SG ceramic resitors on extra Lug , grid resistor hooked up like that ala old 50w marshall and the added 1ohm resitor for bias adj convenience , ( this setup was not standard on these )
bias probe resistors was something that became standard later on but normally these old ones had a 470R SG on socket and grid resistor mounted ala Fender and grounded straight to chassie,

take my word for it

[ic-racer]

Ic-racer, those small ones on the socket are the grid resitors

Agree, but not between 7 and 1 Since it looks like 1 is grounded (for el34) that would be a good place for the other fillament resistor to hook to. but like I said, it is 'hidden' in the pictures.

this amp was probably specially built for both el34 and 6l6 use

,

Again agree. Here is an enlargement of the socket from the layout.

the added 1ohm resitor for bias adj convenience

,

Agree.


Open to suggestions for values, as I cannot really make any of the socket resistor codes out.

I think I can imagine seeing "1K" on the Screen resistors and as you pointed out, would be suited to el34 and 6L6.
The fillament resistors are probably 100r.
The grid resistors??

[ic-racer]

Starting to source components. Looks like Mouser now carries the Hammond Fender replacement transformers and has some of them in stock.

http://www.mouser.com/Search/ProductDet ... hGpw%3d%3d

So, I can get 022871 for the OT.

Since I am going to do a US version I'll use the 120AC PT, 022814, instead of the 022822 that was on #40. Though it looks like Mouser does not stock this one. I'll check and see how long it will take for them to get it.