Guitar Gear Forum

Hey guys, quick update on my humming issue: I bought a tube kit for my JCA50H and replaced all the chinese tubes and also biased at 36-37 mA. The hum is still there and I don't know what to do! Can it be the power outlet is connected? What else can it be? Please, this is the only place where everyone posts regularly. Also, if Grime could appear and comment on this matter, I'd appreciate your input. Thanks!

JackOfBlades wrote:Hey guys, quick update on my humming issue: I bought a tube kit for my JCA50H and replaced all the chinese tubes and also biased at 36-37 mA. The hum is still there and I don't know what to do! Can it be the power outlet is connected? What else can it be? Please, this is the only place where everyone posts regularly. Also, if Grime could appear and comment on this matter, I'd appreciate your input. Thanks!

Hey buddy - wish I had a magic cure for you. Tubes is a good place to start, regardless of the issue - near-guaranteed to massively improve tone.

First thing to do now is try to isolate the source of the noise, by ruling out the way stuff. Have you tried different outlets? Different building? How about changing the power cable? Does it make same sound without the guitar cable plugged in, and have you tried entirely different cable /guitar? What kind of noise - is it a buzzing sound, loud hiss, etc?

Help with depth mod for JCA 50H
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yesterday

Long time reader first time question.

I need help with the depth mod wire placement for my JCA 50H

I have the original schematics and picture Edge11 posted a couple of years ago but they don't match my JCA PCB.

PIC 1 is the original picture posted. It shows the red wire from the pot going to the speaker connection and the black wire from the pot to the PCB marked FB. (Indicated by yellow arrow)



Original.jpg
http://www.harmonycentral.com/t5/image/ ... bl-1&px=-1

PIC 2 is my JCA 50 PCB. There is a diode in the spot where the black wire in the original pic is placed. There is No FB slot.

My board.jpg
http://www.harmonycentral.com/t5/image/ ... bl-1&px=-1

PIC 3 To solve this there is a red wire on my JCA 50 PCB running from the 4 ohm speaker jack to the FB slot on the PCB (Indicated by the yellow arrow). Can I cut the red wire in the middle and place the pot and capacitor in between them. Setting it up as pot to FB on PCB and then pot to 4 ohm speaker jack connection. Is this the right wire connection to hook up the depth mod pot and capacitor?

http://www.harmonycentral.com/t5/image/ ... bl-1&px=-1

Thanks

Yes, you are correct by putting the pot in the middle of that red wire coming from the FB spot on the board. What I did with my 100H was unsolder that wire and just soldered in 2 longer wires - I put my Depth knob in the typical Soldano location on the front panel.

I should have used a different color wire to illustrate the connection, but I think you'll get it.

From those pictures it looks like the 100 and 50 have a different location for the FB, but procedure is the same.

Thanks so much sahlomonic. This is a great forum

bryan12345 wrote:Thanks so much sahlomonic. This is a great forum

Heck yeah it is. Welcome aboard!

Hey Jay,

Are you familiar with the 5150II circuit at all?

I have a Bugera 6262( don't give me shit, it's a backup and it kind of screams lol)!

I've done a few things to tweak it to my tastes but I'm having a hard time shifting the mid frequency on the lead channel. I want to F with the tone stack but the board is super confusing. If I post a link to the schematic would you take a look?

Motocooney wrote:Hey Jay,

Are you familiar with the 5150II circuit at all?

I have a Bugera 6262( don't give me shit, it's a backup and it kind of screams lol)!

I've done a few things to tweak it to my tastes but I'm having a hard time shifting the mid frequency on the lead channel. I want to F with the tone stack but the board is super confusing. If I post a link to the schematic would you take a look?

A Bugera?! Just kidding, dude.

If you have a scheme for the 6262, I'll definitely take a peek for you.

Lol. It sounds pretty fantastic man. I'm shredding through it until the output tranny for my jca100 gets here.
I played a show with it the other night and it sounded huge!!!!
Only complaint is the lead channel is a bit scooped and overly bassy. Perfect for metal but my tone is a little more classic midsy saturated metal type tone.

So far I'm running a 22pf cap on the PI tube pins 7 and 8 to get rid of fizz and sizzle. Just kind of gives amp more of an organic smooth tone. My own words not a descriptin of the mod lol.
Works great. I found it on a 5150 forum. I'm gonna try it on my JCA too.

That's the problem, there's no schem to be found for the 6262. I've been using a 5150 II schem and while there are similarities, it's not the same.

So how can I find the tone stacks for each channel?
I don't even no where to start.

The components arent laid out like the JCA. They're just all in rows.
Also, the board itself is black!
The pots are mounted to a smaller board and there are wires running from that board to the preamp board.

Do you think the tone stack would be on the preamp board or the smaller pot "control" board?

Thanks Jay.
I just snake skinned my JCA50. Plus home made stainless metal grill painted black. Now the depth mod and some pre-amp tubes and I'm set.
Any recommendations for the tubes. I'll post some pics of my amp.

bryan12345 wrote:Thanks Jay.
I just snake skinned my JCA50. Plus home made stainless metal grill painted black. Now the depth mod and some pre-amp tubes and I'm set.
Any recommendations for the tubes. I'll post some pics of my amp.

Depends on what you are looking for as far as tone. You have the stock Chinese tubes in there now? If you also have the stock power tubes, you may want to get a better set as well. Most of us here have found that they are not matched so well out of the gate.

Hey could someone check what kind of knobs are on their JCA? Split shaft or set screw?

I want to order some new knobs and my amp isn't here I can't remember what style the pots/knobs are.

It seems like the pots are split shaft?

A quick reply would be fantastic:)
Thx

Hey could someone check what kind of knobs are on their JCA? Split shaft or set screw?

I want to order some new knobs and my amp isn't here I can't remember what style the pots/knobs are.

It seems like the pots are split shaft?

A quick reply would be fantastic:)
Thx

Mine are split

Depends on what you are looking for as far as tone. You have the stock Chinese tubes in there now? If you also have the stock power tubes, you may want to get a better set as well. Most of us here have found that they are not matched so well out of the gate.

I still have all the stock chinese tubes in it. I like the George Lynch Tone. Can switching just the pre amp tubes be enough for that and what type of pre amp tubes can achieve this. Also I did the depth mod but the change in tone wasn't as drastic as I thought it would be or as some people make it out to be. Hope The parts I used where the proper ones.
1. Alpha 1M pot from "Amplified Parts" part # R-V38-1MA
2 Orange Drop Polypropylene Film capacitor .0047 uf @ 400V Part# C-PD0047-400

Hey Jay and sahlomonic,

Here are some pics of my half stack. The JCA 50 has Stainless steel grill painted black with snake skin and the cabinet has the Stainless steel grill on it no paint.
Still thinking about wrapping the cabinet with snake skin, it's just alot of work.
Thank you for all the help.
[https://www.dropbox.com/s/ztd0q1ymqvbg6xc/20140210_132620.jpg]
[https://www.dropbox.com/s/gpe8dj68qzy4xt3/20140210_133545-1.jpg
[https://www.dropbox.com/s/u5bif99ghoueuv5/20140210_133510.jpg]
[https://www.dropbox.com/s/2bah98wjgod9fli/20140210_133125.jpg]

Let me try the post again.
Didn't work the first time.

[http://s123.photobucket.com/user/lmb65/media/JCA%20Amp/20140210_132620_zps8c74ed8d.jpg.html][/img]
[http://s123.photobucket.com/user/lmb65/media/JCA%20Amp/20140210_133545-1_zps56ba2c6f.jpg.html][/img]
[http://s123.photobucket.com/user/lmb65/media/JCA%20Amp/20140210_133510_zps633b5794.jpg.html][/img]
[http://s123.photobucket.com/user/lmb65/media/JCA%20Amp/20140210_133125_zps591e0ad8.jpg.html][/img]

Sorry guys, having trouble posting these pics, hope this works. If not I'm done.

[img][IMG]http://i123.photobucket.com/albums/o299/lmb65/JCA%20Amp/20140210_132620_zps8c74ed8d.jpg[/img][/img]
[img][IMG]http://i123.photobucket.com/albums/o299/lmb65/JCA%20Amp/20140210_133545-1_zps56ba2c6f.jpg[/img][/img]
[img][IMG]http://i123.photobucket.com/albums/o299/lmb65/JCA%20Amp/20140210_133510_zps633b5794.jpg[/img][/img]
[img][IMG]http://i123.photobucket.com/albums/o299/lmb65/JCA%20Amp/20140210_133125_zps591e0ad8.jpg[/img][/img]

bryan12345 wrote:Sorry guys, having trouble posting these pics, hope this works. If not I'm done.

[img][IMG]http://i123.photobucket.com/albums/o299/lmb65/JCA%20Amp/20140210_132620_zps8c74ed8d.jpg[/img][/img]
[img][IMG]http://i123.photobucket.com/albums/o299/lmb65/JCA%20Amp/20140210_133545-1_zps56ba2c6f.jpg[/img][/img]
[img][IMG]http://i123.photobucket.com/albums/o299/lmb65/JCA%20Amp/20140210_133510_zps633b5794.jpg[/img][/img]
[img][IMG]http://i123.photobucket.com/albums/o299/lmb65/JCA%20Amp/20140210_133125_zps591e0ad8.jpg[/img][/img]

Here, lemme help you out. Next time, just click the "IMG" box in photobucket and paste directly here (don't use the Img button above the forum post). Here's yer images





Like the snakeskin a lot - great job!

Thanks Grimespace that was awesome. I'm a firefighter not much of a techi

Jay wrote:A Bugera?! Just kidding, dude.

If you have a scheme for the 6262, I'll definitely take a peek for you.

I found a schematic, how the hell do I attach a link to the PDF?
http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&sqi=2&ved=0CCcQFjAA&url=http%3A%2F%2Fmusic-electronics-forum.com%2Fattachments%2F26490d1385647822-6262-revf.pdf&ei=O9T_UuKDKcupqwGyroCgAw&usg=AFQjCNF9iOMoQdmJWLyx2JMeXTj7Zpky4w&sig2=q26uz3dlQYTgq-dcrdNypA&bvm=bv.61535280,d.aWM

bryan12345 wrote:Depends on what you are looking for as far as tone. You have the stock Chinese tubes in there now? If you also have the stock power tubes, you may want to get a better set as well. Most of us here have found that they are not matched so well out of the gate.

I still have all the stock chinese tubes in it. I like the George Lynch Tone. Can switching just the pre amp tubes be enough for that and what type of pre amp tubes can achieve this. Also I did the depth mod but the change in tone wasn't as drastic as I thought it would be or as some people make it out to be. Hope The parts I used where the proper ones.
1. Alpha 1M pot from "Amplified Parts" part # R-V38-1MA
2 Orange Drop Polypropylene Film capacitor .0047 uf @ 400V Part# C-PD0047-400

1M log potentiometer would be preferred, either will work though. Looks like you have the right cap. I have the mod on my jca22h and it is noticeable.

hi guys, I'm new around here, i've been lurking around the internet trying to find an answer without much success.. and I would apprecciate if any of you could help me,

anyway so i recently bought a jca2112rc (the old model) at a pretty good price and I'm pretty happy with it...BUT on the back it has another jack input which was clearly made by the former owner of it, it's just a jack that goes to what I believe is "C7". Any of you have any idea what for?

I'm attaching some pics (sorry for the quality)





thanks for your time!

bryan12345 wrote:Hey Jay and sahlomonic,

Here are some pics of my half stack. The JCA 50 has Stainless steel grill painted black with snake skin and the cabinet has the Stainless steel grill on it no paint.
Still thinking about wrapping the cabinet with snake skin, it's just alot of work.
Thank you for all the help.
[https://www.dropbox.com/s/ztd0q1ymqvbg6xc/20140210_132620.jpg]
[https://www.dropbox.com/s/gpe8dj68qzy4xt3/20140210_133545-1.jpg
[https://www.dropbox.com/s/u5bif99ghoueuv5/20140210_133510.jpg]
[https://www.dropbox.com/s/2bah98wjgod9fli/20140210_133125.jpg]

Dude, that snakeskin looks KILLER. I really like that particular shade. Please share where you got it!

Good to see that the Jet city mod community is still going strong.
Have any of you boys gotten the 20v yet?