British flavored 5F1 layout. Sanity check for me, please?

[Quixote]

Hey all! I'm trying to layout a eyelet board for a modified Selmer Futurama Corvette amp from the 60's. Realizing just how small this circuit is, I tried to omit the tremolo circuit, only leaving in the single 12AX7 and EL84. Should just be a single ended amp, SUPER simple and bare-bones, to the point where I'm not even sure this would 100% work.

Does anyone with far more wisdom know at a glance if this is going to work? Something about the 47nF cathode bypass cap on V1B is making me really skeptical, but it's what the original schematic calls for I guess. Same with the whole .01uF coupling cap thing. I'm just not 100% sure.

Also if someone could double check my power supply wiring, I would be infinitely appreciative. This is the first time I've messed around with an EZ80 Rec tube.

Also yes, I did download and rework the DIYLC 5F1 file hahaha!

[Quixote]

Immediately noticed an issue with the load resistors for V1 being in parallel instead of feeding each plate individually. Whoops. Here's my revised layout.

[sluckey]

1. Need a 1M resistor on the input jack connected between tip and sleeve.

2. V1 pin 7 must have a resistor to ground. I suggest 1M.

3. VOL pot surely isn't 5M. 500K would be fine.

4. TONE pot surely isn't 100M. 1M should be fine.

5. Are you sure the PT yellow wires are 6.3V? I suggest using the yellow wires for the pilot light and connect the green wires to the EZ80. Then daisy chain the green wires to the other two tubes.

[Quixote]

1. Ahh, the anti-pop resistor. Gottcha!

2. I didn't think it mattered all that much, but the tremolo 'intensity' knob I'm omitting was indeed a 1M potentiometer.

3. & 4. Yeaah I dunno about that one either. I'll link the schematics for the Selmer as well to cross-reference but it might just be the pictures. Those sound far more reasonable values. Everything else value-wise sounds right?

5. I'm not 100% sure. Looks like there actually is only a single heater line tap coming off the transformer, and that's at 6.3v. I was planning to retrofit a 5F1 power transformer in here to replace that though, since those I imagine would be far easier to source.

I'll go ahead and attach both files. Does this look sufficient enough? I don't know how I feel about the grid wire running over B+ but I can't imagine that being a huge issue. Thank you so much though!

[PRR]

...3. VOL pot surely isn't 5M. 500K would be fine....

Perhaps spelled ".5M" ??

Maybe clearer on the SPEED pot.

Another reminder to use leading zeros. Never start a number with a dot if you are going to FAX or Xerox it.

[Quixote]

...3. VOL pot surely isn't 5M. 500K would be fine....

Perhaps spelled ".5M" ??

Maybe clearer on the SPEED pot.

Another reminder to use leading zeros. Never start a number with a dot if you are going to FAX or Xerox it.

DUDE! Brilliant. Most old amps I've serviced usually are either super clear PDF scans like Hammonds, or the actual piece of paper glued to the inside. Thanks for helping me decipher that hahaha!

Any ideas as to what that tone cap could be? It's such a weird design, slammed between preamp and power amp. Would it be wise to audition a 0.047nF cap like in a 5E3 deluxe? I might be able to sniff around some pics of the circuit board to find out exactly what it is.

[sluckey]

It's a simple treble bleed tone circuit. Just use a .01µF.

[PRR]

...Any ideas as to what that tone cap could be? It's such a weird design, ....

There's no good answer. The circuit impedance there varies from zero to 250k. You don't need anybody's permission to start trial/error.

Or see if you can find a similar plan.

Remember that commercial amp knobs aren't always useful. Fender's Mid and Presence are dubious to many ears. But less knobs is "less value" on the showroom floor, so you never want to leave one off.

[bmccowan]

Ted Weber has a similar design; Smokin' Joe 1. Bare bones - same tubes except rectifier which is SS - Vol/Tone/MV. The schematic and layout are in the Weber DIY section.
I mostly followed that schematic years ago but used a tube rectifier. I did not use their chassis as it required mounting the board right over the tube sockets. What were they thinking?
I think its worth looking at the schematic.
I eventually converted it to a single 6L6, but the amp cranked just fine with the EL84.

[Lectroid]

@bmmcowan,

I just checked Weber's site, it doesn't seem to be serving up schematics or layouts anymore for several amps, incl. Smoking' Joe.  Just the BOMs.  Unless you know a back door?

[sluckey]

@bmmcowan,

I just checked Weber's site, it doesn't seem to be serving up schematics or layouts anymore for several amps, incl. Smoking' Joe.  Just the BOMs.  Unless you know a back door?

Check the front door...

     https://www.tedweber.com/diy-kits/

[shooter]

Never start a number with a dot

Worked for a Doc born in Brazil, his favorite insult "That one is 3 zeros to the left"