Picked up a Jca20 from GC for $200 to try it out, and a 1960B for $238. I remember reading the the Jose/Browneye wasn't to hard to do? Are their any tutorials, schematics, parts list etc.?
http://mrfarva.imgur.com/all/" onclick="window.open(this.href);return false;
Jca20 Jose Mod Difficult For Beginner?
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Re: Jca20 Jose Mod Difficult For Beginner?
Nice score.
Here's a schematic I found that shows what to change to make your amp Jose spec..I was just looking at this earlier today. It showed up in google images when I was searching for Jose High Gain Mod.. Lucky you
NOTE: V2 is mislabled as V1. V1 is on the left. Also, notice on the schematic the big brown dots highlighting changed values, and no label next to added values like the 100k and 470pf added to v1a plate in step 1 for example.
This isn't too difficult for a beginner imo. Just follow safety procedures, Uplug the amp, and drain your caps before working on it so you don't kill yourself. If you don't know how.. Just ask, or hire a pro.
$10 to $20 in parts, and 30 minutes to perform the changes.
Here's a quick parts list and instructions I made up to help.
Parts list:
3) 470pf
100k ( or 330k)**
.68uf
2) 68k
470k
Instructions:
Step1)
Add 100k in series with r28 220k and then put a 470pf across it ( or replace 220k r28 with 330k and put the 470pf across that instead)**
Step2)
Add .68uf across the 2.7k r25
(Wow it's not already there. It's like a 2204 with a 2.7k instead of a 10k interesting)
Step3)
Add 68k from v1 pin 2 to in between r53 and vr6*
Step4) Jump r32
Step5)Remove c23
Step6) Cut trace between r36 and c23
Step7) Add 470k from r36 to ground and add 470pf across it
Step 8 )add 470pf across r36
Step9)Replace r33 with 1m pot that used to be vr6
Step 10) Optional 33k r21 slope resister.
*vr6 used to be a 1m pot, now is a 68k. Vr6 is moved to replace r33.. Not moved from where it's mounted, just how it's connected to match the edited schematic.
Have fun
Here's a schematic I found that shows what to change to make your amp Jose spec..I was just looking at this earlier today. It showed up in google images when I was searching for Jose High Gain Mod.. Lucky you
NOTE: V2 is mislabled as V1. V1 is on the left. Also, notice on the schematic the big brown dots highlighting changed values, and no label next to added values like the 100k and 470pf added to v1a plate in step 1 for example.
This isn't too difficult for a beginner imo. Just follow safety procedures, Uplug the amp, and drain your caps before working on it so you don't kill yourself. If you don't know how.. Just ask, or hire a pro.
$10 to $20 in parts, and 30 minutes to perform the changes.
Here's a quick parts list and instructions I made up to help.
Parts list:
3) 470pf
100k ( or 330k)**
.68uf
2) 68k
470k
Instructions:
Step1)
Add 100k in series with r28 220k and then put a 470pf across it ( or replace 220k r28 with 330k and put the 470pf across that instead)**
Step2)
Add .68uf across the 2.7k r25
(Wow it's not already there. It's like a 2204 with a 2.7k instead of a 10k interesting)
Step3)
Add 68k from v1 pin 2 to in between r53 and vr6*
Step4) Jump r32
Step5)Remove c23
Step6) Cut trace between r36 and c23
Step7) Add 470k from r36 to ground and add 470pf across it
Step 8 )add 470pf across r36
Step9)Replace r33 with 1m pot that used to be vr6
Step 10) Optional 33k r21 slope resister.
*vr6 used to be a 1m pot, now is a 68k. Vr6 is moved to replace r33.. Not moved from where it's mounted, just how it's connected to match the edited schematic.
Have fun
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Re: Jca20 Jose Mod Difficult For Beginner?
After all that I found the source....
http://www.harmonycentral.com/t5/Amps/J ... p/28031120" onclick="window.open(this.href);return false;
http://www.harmonycentral.com/t5/Amps/J ... p/28031120" onclick="window.open(this.href);return false;
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Re: Jca20 Jose Mod Difficult For Beginner?
Thank you! Still debating if I'm going to attempt this mod or just return the amp... Can I order the parts from valve storm, or just go to radio shack? I would also like to add a SAT switch. Assuming I'll have to pull the board out of the chassis? Also wondering how I drain the amp. A double ended alligator clip wire?
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Re: Jca20 Jose Mod Difficult For Beginner?
Yes Valvestorm
I don't think you will have to take put the PCB... All the parts look accessable from your pic. Remember you're not actually moving the pot, just the trace
Yes a clip wire from v1a plate to ground. (That's wbere the 220k in step1 is) I like putting a nice power resister on the wire to eliminate popping. There's a thread here on draining caps if you do a search.
I don't think you will have to take put the PCB... All the parts look accessable from your pic. Remember you're not actually moving the pot, just the trace
Yes a clip wire from v1a plate to ground. (That's wbere the 220k in step1 is) I like putting a nice power resister on the wire to eliminate popping. There's a thread here on draining caps if you do a search.
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Re: Jca20 Jose Mod Difficult For Beginner?
So I turned it on today and noticed a sound, sounded like I was wigging my guitar cable. Looked at the back and saw one of the power tubes glowing red. Only does it off standby. Swapped tubes and it does it in the same socket. Pulled the chassis checked all of the solder joints, none of them wiggled. Any ideas? Theirs no fuse on the back of the amp?
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Re: Jca20 Jose Mod Difficult For Beginner?
This is a good thread for you:
http://forum.metroamp.com/viewtopic.php ... 6&start=15" onclick="window.open(this.href);return false;
AND
http://forum.metroamp.com/viewtopic.php?f=10&t=31746" onclick="window.open(this.href);return false;
http://forum.metroamp.com/viewtopic.php ... 6&start=15" onclick="window.open(this.href);return false;
AND
http://forum.metroamp.com/viewtopic.php?f=10&t=31746" onclick="window.open(this.href);return false;