Matchless C30 pre/Chieftain power built in a Traynor YBA-1 (schematic enclosed)

[Duncan]

Looking for feedback on the attached schematic. I've married the C30 and Chieftain schems together, and I'd love a second set of eyes to make sure I've not left anything out.

I used Digikey's schematic builder, so I didn't bother with the power transformer diagram, you can see the diode stack where the HV enters the chain.

Thanks in advance!

[Willabe]

You need edit it down to just the schematic. Can't read it like it is now.

[Duncan]

Sorry about that! I've uploaded a new one that should be much better.

[Willabe]

Thank you. 

[Willabe]

You have 2 B+ filter cap nodes labeled as B4.

PI has no plate load resistors.

You don't need a choke with that high a current rating. A Fender Twin has only 90mA and its 4 power tube screens and 6 x 12AX7.

Might be other things. 

[Leevi]

Based on my experience regarding Vox/Matchless power amps the 1M crossline master pot does not work in an optimal way. I would change it to 250K log or 500K log pot.


/Leevi

[Duncan]

You have 2 B+ filter cap nodes labeled as B4.

PI has no plate load resistors.

You don't need a choke with that high a current rating. A Fender Twin has only 90mA and its 4 power tube screens and 6 x 12AX7.

Might be other things. 

Whoops. Good catch on the mislabeled B+ nodes and the PI. Will correct.

Yeah the choke specs were pulled from the DC30 schematic in the schematic library on here. I’ll probably end up using the same choke as what I used in my chieftain build.

[Duncan]

Based on my experience regarding Vox/Matchless power amps the 1M crossline master pot does not work in an optimal way. I would change it to 250K log or 500K log pot.


/Leevi

Interesting. I’ll definitely give a 500K log a go!

Thank you!

[shooter]

I tried the cross-fade once, none of the guitarists liked it

[Willabe]

Yeah the choke specs were pulled from the DC30 schematic in the schematic library on here. I’ll probably end up using the same choke as what I used in my chieftain build.

It's just a size/chassis space thing.

I'm not sure that DC30 schematic is really done by Matchless.   

[Duncan]

Yeah the choke I used in my chieftain build is a 50H 125ma

[Willabe]

Yeah the choke I used in my chieftain build is a 50H 125ma

That's way over kill too.

[Duncan]

Yeah the choke I used in my chieftain build is a 50H 125ma

That's way over kill too.

I actually dug out a choke I salvaged from an old Hammond organ (10H @75ma) that’ll probably use!

[Duncan]

Here's an updated schematic with a LarMar MV and a few other corrections.

Really, I'm mostly curious if anyone sees an issue with 50 uF filter caps or the .022 uF coupling caps after the PI.

[shooter]

curious if anyone sees an issue with 50 uF filter caps

other than being labeled 250uF and one not connected, nope.  I typically use 47uf at PA cathodes.

[Willabe]

Now get your grounding right before you start to wire it up.

https://www.valvewizard.co.uk/Grounding.html

[Duncan]

curious if anyone sees an issue with 50 uF filter caps

other than being labeled 250uF and one not connected, nope.  I typically use 47uf at PA cathodes.

Good catch on it not being connected. A miss on my end.

But those ones aren't the filter caps I'm referring to. I was referencing the ones on either side of the choke.

[shooter]

I'm mostly curious if anyone sees an issue with 50 uF filter caps or the .022 uF coupling caps after the PI.

we flunked the same English class 


....the PS CLC filter....
no I don't see a problem unless they're running at the 450vdc rating

[Duncan]

I've been looking around at LarMar MVs on cathode biased circuits, and I just can't find very many examples of how its done. Can someone weigh in on that part?