Cloned a Friedman modded JCA20H

  • Thread starter Thread starter sahlomonic
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sahlomonic

sahlomonic

Well-known member
This is a work in progress, but as I posted in the main forum, this started out as a trainwreck that I bought years ago. Board was burned up pretty bad, and had a ton of mods that just sounded awful sounding (some were ok to be honest, but implemented poorly). I deconstructed it back to stock form, replaced a few pots, and started cloning a Friedman modded JCA20H I'm selling back to my buddy.

Again, still a work in progress, but here's the gut shots of it fully functional. Right now I'm in the middle of upgrading the OT, and next phase is cleaning up the board best I can and re-doing the work I did to make it more aesthetically pleasing and doing it right. This is just to test functionality. Will be using quite a bit of heat shrink on the raised components. Not bad for really a few bucks in parts. I'm certainly no pro at this, but I'm happy with the progress so far.

Resources were a BE100 schematic I found online, the host amp which Dave modded himself, and parts of a mod tutorial from Edge11 from the GGF fourm.

FriedmanClone1 (1).jpg


Gut shot

FriedmanClone1 (2).jpg



SAT switch (Jose diode clipping)

FriedmanClone1 (3).jpg


YUCK


FriedmanClone1 (4).jpg


Gain pot moved after 2nd gain stage (wired under the board with cut traces for now)
 
Whew, that board is a mess. ?

Here is mine for reference. I love my amp. ?

1644378599429.jpeg
 
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psychodave said:
Whew, that board is a mess. ?

Here is mine for reference. I love my amp. ?

View attachment 106846
Click to expand...
Very nice. That's very similar to my host amp that Dave modded, but mine doesn't have Wima's. What's the switch on the gain pot? And what's the 68k resistor coming off V1 grid bypassed with (orange disc cap)? What's R28 bypassed with?
 
harddriver said:
Does your Jet City have a Jose Master Volume setup or a JCM800 Pre-PI Master volume Dave?
Click to expand...
If memory serves me, the master location is stock, but the clipping is post tone stack? I honestly never drew it out and don't remember... Mark told me what to do here and outside of different diodes/transistors, I never tinkered with it.
 
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sahlomonic said:
Very nice. That's very similar to my host amp that Dave modded, but mine doesn't have Wima's. What's the switch on the gain pot? And what's the 68k resistor coming off V1 grid bypassed with (orange disc cap)? What's R28 bypassed with?
Click to expand...
Switch on the gain pot are bright switches (.0022 and .0047). The cap off the 68k is 0.001uf. R28 snubber is 47pf (I don't like the 500pf Friedman uses).
 
sahlomonic said:
This is a work in progress, but as I posted in the main forum, this started out as a trainwreck that I bought years ago. Board was burned up pretty bad, and had a ton of mods that just sounded awful sounding (some were ok to be honest, but implemented poorly). I deconstructed it back to stock form, replaced a few pots, and started cloning a Friedman modded JCA20H I'm selling back to my buddy.

Again, still a work in progress, but here's the gut shots of it fully functional. Right now I'm in the middle of upgrading the OT, and next phase is cleaning up the board best I can and re-doing the work I did to make it more aesthetically pleasing and doing it right. This is just to test functionality. Will be using quite a bit of heat shrink on the raised components. Not bad for really a few bucks in parts. I'm certainly no pro at this, but I'm happy with the progress so far.

Resources were a BE100 schematic I found online, the host amp which Dave modded himself, and parts of a mod tutorial from Edge11 from the GGF fourm.

View attachment 106771

Gut shot

View attachment 106774


SAT switch (Jose diode clipping)

View attachment 106777

YUCK


View attachment 106780

Gain pot moved after 2nd gain stage (wired under the board with cut traces for now)
Click to expand...
It's cool. Build up looks nice. And well done.
 
psychodave said:
Whew, that board is a mess. ?

Here is mine for reference. I love my amp. ?

Dave, did you cut any traces with your design? I may be confusing your amp with some of the other mod posts/threads.
Click to expand...
 
The actual Friedman modded JCA20H has cut traces for the gain pot, same as I outlined in my pic.
 
PXL_20220211_000657656.jpg


No I am not color blind. New (old) OT was incorrectly color coded from the manufacturer. Also worth noting they sound great when you reverse the polarity :p
 
psychodave said:
How did you figure that out?
Click to expand...
When I first wired it up years ago on another amp, I was met with a nice, subtle - no scratch that - LOUD SQUEAL when I flipped it off standby. Reversed the wires and was good to go. Promptly talked to Doug at Jet City to let him know, and he later confirmed from the manufacturer that the colors were swapped.
 
sahlomonic said:
When I first wired it up years ago on another amp, I was met with a nice, subtle - no scratch that - LOUD SQUEAL when I flipped it off standby. Reversed the wires and was good to go. Promptly talked to Doug at Jet City to let him know, and he later confirmed from the manufacturer that the colors were swapped.
Click to expand...
Interesting. So they are all like that? All of mine are super old... with metal switches.
 
sahlomonic said:
No this was a particular aftermarket OT that was color coded wrong.
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I'm using a transformer by classic tone. I bought two of them a few years ago. Seems Classic tone isnt making these anymore.
 
psychodave said:
I'm using a transformer by classic tone. I bought two of them a few years ago. Seems Classic tone isnt making these anymore.
Click to expand...
I have one as well on another JCA20H. I believe Classic Tone went out of business within the last year or so?
 
sahlomonic said:
I have one as well on another JCA20H. I believe Classic Tone went out of business within the last year or so?
Click to expand...
I believe they went out of business. Stinks.

Glad I bought two classic tone output transformers. I have another JCA20 I'm tinkering with.
 
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