Dumble Modded Bassman Layout/Schematic

[pompeiisneaks]

Edit:

Re read... looks like you mean the 2 100uF's and their droppers are still B+1 but move left of the choke, and there's no R44 between B+4 and B+5?

~Phil

[Charlie Wilson]

Yes, just like Aaron's schematic.
CW

[pompeiisneaks]

Okay fixed, I think...

~Phil

[Charlie Wilson]

Phil, hate to be a pest but I really think the switch is a jazz/rock not deep. Also, Aaron's schematic is not correct with regards to the jazz/rock. He has the connections for the 100k and .005 cap reversed from what is on the 124 schematic. The little drawing I did seems to jive with the 124 schematic and the photos.
CW

[pompeiisneaks]

Phil, hate to be a pest but I really think the switch is a jazz/rock not deep. Also, Aaron's schematic is not correct with regards to the jazz/rock. He has the connections for the 100k and .005 cap reversed from what is on the 124 schematic. The little drawing I did seems to jive with the 124 schematic and the photos.
CW

I did my schematic and layout based on what I thought was your design? no? I rebranded it deep on the schematic at one point when I wasn't sure which it was, but if you can point out where I've got the error, I'll be glad to fix it.

~Phil

[Charlie Wilson]

I think almost. The 100k goes to the top of the volume which is also the wiper of the treble.
CW

[pompeiisneaks]

I was just looking at the layout and going... it's right... huh? Then I realized you might be looking at the schematic, and was like OH it's wrong there for sure

Thanks for catching that.

~Phil

[pompeiisneaks]

Okay updated.

Thanks Charlie!

If anyone knows KiCad very well I think, if you look at the bias section, I've done the ac power side wrong, if I do a net rules check it always complains about it not being connected. I don't know why... I've given it a label, but do I just have to put some random DC (even though it's AC and I can't find any 'part' for an IEC connection etc in there) to be the 'power source'? This might be better asked elsewhere, but hoping someone might have an idea?

~Phil

[didit]

Hello --

Looks quite complete and correct based upon just a brief scan, with more time planned to look later. One quick thought. We doubtless never will know what was put inside that "doghouse" but a good guess would be greater than 20uF per node. Inclined to suggest lift off JCM800 like most of the rest of the circuit. Unable to help with KiCAD though do use it occasionally, way far from expert. I struggled with grounds for a bit and then sorted it. Asking on one of the KiCAD topical forums is wise, but you knew that already.

Best .. Ian

[Charlie Wilson]

Yeah, I'm going to agree with Ian about the filter capacitors. Dumble does seem to like up the filtering in his modified Fender creations.
CW

[pompeiisneaks]

Ok sounds good, I'll bump the filtering to 50uF per node instead of the 20uF of the fender style.

I'll update the schematic shortly.

~Phil

[norburybrook]

Ok sounds good, I'll bump the filtering to 50uF per node instead of the 20uF of the fender style.

I'll update the schematic shortly.

~Phil

F&T do 33uF or 47uF


M

[didit]

Hello -

Reading the JCM800 schematic it appears they did dual 50uF with a common ground. Both F&T and JJ source this as a "can", which are compact and inexpensive. They also source similar 32 x 2.

Best .. Ian

[pompeiisneaks]

Hello -

Reading the JCM800 schematic it appears they did dual 50uF with a common ground. Both F&T and JJ source this as a "can", which are compact and inexpensive. They also source similar 32 x 2.

Best .. Ian

Yup exactly, that's basically what I did with my sluckey's jcm800/jmp hybrid amp I built recently, used a 3 in 1 50/50/50 can for the build and it worked great, and not too expensive,

CeDist has

https://www.cedist.com/products/capacit ... ectrolytic
and
https://www.cedist.com/products/capacit ... ectrolytic

with dual 50/50 I can't recall where I got my triple, but they even have a quad 50/50/50/50 but I don't think I want that many of my nodes with common grounds.
https://www.cedist.com/products/capacit ... 50505050-f

~Phil

[Aaron]

Hi Phil,
I can’t see the 100k feedback resistor on your schematic.

Charlie,
You’re right, I can see the capacitor wire bent back round on the Jazz/Rock switch on another photo.

Thanks,
Aaron