JCA OWNERS!!! (RE)JOIN THE JET CITY LOUNGE!!!

[midnightlaundry]

Has anyone put a Metro Loop in one if these amps?

Huh?

[Tortuga]

Has anyone put a Metro Loop in one if these amps?

Huh?

I think it's been tried - certainly remember ppl talking about it, but nobody came back talking 'holy grail' or anything like that. The loop just hasn't been solved.

[käsebrot]

Kasebrot, I didn't see your response until just now.

Thanks for the help! I put C20 and R9 back in the circuit and prefer it that way...which makes sense, after receiving your information. I pulled a leg from C6 and C7 (which seems to be the bright cap for the "Crunch Channel") and I'm loving the tone this way. I can actually use the treble and presence controls now without that awful "ice pick" high end.

As for the other suggestions you made, could you give me the actual numbers on the PCB? I'm still learning the lingo, so I need the "For Dummies" version. I appreciate your patience with me!

I would put back C7, if you like less gain in the Crunch Channel, then try 220p there.

What you've requested:

- R5 and R9 from 1M to 470k
- VR1 and VR2 from A1M to A500k
- C5 from 1n to 2,2n
- C6 from 470p to 1n

Those 4 steps must be done at once.

What you also can do:

- C2 and C9 from 22n to 10n
- C8 from 1u to 680n

What I recommend:

- swap out all ceramics up to 1n and exchange them with good high voltage ceramics (f.e. Murata 2kV), you can also use Silver Mica - but not the cheap ones, try Cornell Dubilier SM
- swap out all coupling caps and use Roederstein MKT1813 or Mallory 150 in the front of the signal and Sozo Standard in the end (coupling cap to PI, in the PI, also Presence)

But overall, most important thing is to bias the power tubes properly (19mA for 22H) and use good preamp tubes (f.e. Ruby 12AX7 AC5)!

[shep]

i payed 40 bucks for a new transformer for a jca50. talk to doug at jet city. he will get you one

[midnightlaundry]

Has anyone put a Metro Loop in one if these amps?

Huh?

I think it's been tried - certainly remember ppl talking about it, but nobody came back talking 'holy grail' or anything like that. The loop just hasn't been solved.

I bet it works good. I read that it's supposed to go after the tone stack. The FX loop on the 50 comes in before the cathode follower. So if people are using the existing fx loop, they might not get the full benefit.

[Hipster Salad]

Per kasebrot's suggestions I ordered a batch of parts over the holiday break (as well as all new Alpha pots), and coming from UK may take a couple weeks. Fingers crossed, and hopefully I can figure out what that stupid no-bass/no-mid problem was.

[Tortuga]

Per kasebrot's suggestions I ordered a batch of parts over the holiday break (as well as all new Alpha pots), and coming from UK may take a couple weeks. Fingers crossed, and hopefully I can figure out what that stupid no-bass/no-mid problem was.

Damn, man - I totally forgot about this - you never got it resolved, eh?

[marnold]

I took an old demo from a band I used to be in and re-recorded my guitar parts with the JCA2212c. See the description for details. I'm not super happy with the tone, because it sounded MUCH better in the room, but oh well. Here it is!

https://soundcloud.com/briggsaudioprodu ... oostedboth

I agree with the other comments. Sounds pretty sweet to me too!

[Hipster Salad]

Per kasebrot's suggestions I ordered a batch of parts over the holiday break (as well as all new Alpha pots), and coming from UK may take a couple weeks. Fingers crossed, and hopefully I can figure out what that stupid no-bass/no-mid problem was.

Damn, man - I totally forgot about this - you never got it resolved, eh?

Nope :/ Been sitting on the bench since I got it off a trade. But, it's not like I have 2 other Jet City amps to jam on or anything

[Tortuga]

I think you need to repost those gut shots (maybe even a bit more detail on the mods) from the new one here, Sahl. Did you get any clips of it yet?

[Hipster Salad]

Sure thing grime!

Just bought this from my other guitarist - he has a Shiva and just bought an EVH mini so didn't play the Jet City hardly at all anymore. Yay me!

Mods are:

Naked channel - simple clean with no EQ or gain control, just volume and is footswitchable. No bright switch. Also adds a Metro effects loop that can be bypassed.
SAT - diode clipping circuit that adds a little more gain and compression, and boosts the volume a little
BE - the Brown Eye mod. Basically taken from the famous Jose HG mod.

Check the prices on Friedman's website for all of those mods

This. Will. Do. Brown. Sound. I put an Alesis rack unit in the effects loop, and with some good reverb this can hang with the first 2 VH albums no sweat!



Gut shot




You can see a couple spots where the traces were cut. Not as intrusive as I would have thought to be honest. Could it be that this is what led Friedman to make the Pink Taco/PT20? I read on the Racksystems board that someone said it (PT20) looked like a modded Soldano Atomic 16.

I'm no expert, but a few of these solder joints look suspect. If you guys think there is reason to worry, I'll strip them and re-solder.




Short crappy clip. I actually recorded the riff to send to my drummer to get his opinion haha. Going through a pair of Lynchbacks. Volume at maybe 0.5. Just set it up so didn't tweak the EQ like I should have. Gain at 4 o'clock, mids and treble dimed, bass noon (although should have been much higher in retrospect)

[video]https://www.youtube.com/watch?v=LS1XwScb5GY[/video]

[Hipster Salad]

Update on the JCA50H woes . . .

Got all new pots, and 2 caps + 2 resistors because I was changing the gain pots to 500k.


I did bugger up one of the top eyelets at C21, but the trace seems undamaged from the bottom, and continuity tests check out OK.



I now have middle control, but still no bass control, and the treble control is now funky, as in it acts in reverse. Roll it from 9 to 0, and signal increases.



B250k pot for Treble VR5, correct (stock value)?

I'm at a loss now . . .

[shep]

your probably using the wrong treble pot. make sure its the right one whether its log or lin (a or b). i believe if its the wrong pot the pot would work in reverse. ive had it happen before. the original pot should have some identifying markings on it somewhere. according to the schematic it is b250k. but i would look at the original and or try a different pot maybe an a250k

[Hipster Salad]

That's what I assume as well, but right off the schematic for the 50H it says B250k, and that's exactly what the Treble pot I installed is labeled.

Unless I'm having an oversight . . .

[Hipster Salad]

Aaaaaaaand I think I see a problem after I posted that pic. I don't know if it explains the issues I'm having, but looks like I ordered A1k pots instead of A1M.


I had one stock A1M pot lying around so I wired that for the Bass control. EQ controls behave like this currently: Bass works in REVERSE, Middle works fine, Treble works in REVERSE.

I'm just going to wait until my new order of stuff comes in next week and go from there.

[shep]

well at least ya got it working again. your in the right direction. just gotta get the right pots.

[TommyTee]

Hi guys, just a quick question. Are the mods presented throughout these boards applicable to both the JCA 22, JCA 50 etc? That is, apart from the differences in component numbering/labelling between the 50 and 22 within their schematics, are the component values the same for each amp? For example if the mod suggests a slope resistor value of 39K for a jca22, would the same value apply for a jca50 for the same component within the circuit? and would this also apply for capacitor values as well.

Looking forward to your response.

[shep]

Hi guys, just a quick question. Are the mods presented throughout these boards applicable to both the JCA 22, JCA 50 etc? That is, apart from the differences in component numbering/labelling between the 50 and 22 within their schematics, are the component values the same for each amp? For example if the mod suggests a slope resistor value of 39K for a jca22, would the same value apply for a jca50 for the same component within the circuit? and would this also apply for capacitor values as well.

Looking forward to your response.

not in every instense the values are the same. most mods that are published in this website are universal, but not all cap and resistor values are the same between the 22 and the 50. the slope resistor values is the same. both schematics are on this website. it is easy to just
compare them.

[TommyTee]

Hi Shep, I suspected as much thanks, I will compare each of the schematics and determine the appropriate values for my JCA50.

TT

[Dunlop]

Hi guys
I am thinking about re-capping my 20h. Those stock blue caps are polypropylene?
What would you choose for recapp? Wima, orange drops or mallory?

[Drainbamage]

service manual says they are metal oxide film capacitor

[msours]

Lost my SLO in a divorce, downsized to a Jet City 100HDM... I've been crawling the boards looking for mods, does anyone know what I need todo to tame the top end fizz and possibly make the amp a little warmer/creamer?

So far I've swamped the power tubes out for JJ's (although I probably should be using the Svetlana 6L6GC's, its what I ran in the SLO. And I've replaced all of the pre amp tubes with jj's and ruby's HG's. Probably should pull the rest of the Ruby's and swamp with jj's..

I know I applied the Warren Haynes mod to the SLO (removal of a cap), is there an equivalent mod for the 100? Anyone got any suggestions?

I was really surprised by this amp, even my SLO with stock tubes kinda smelled when I first bought it - I know I can make this amp rock with a little sweat.

Thanks

[Hipster Salad]

Another progress update:

Got in the correct pots for OD volume, Normal volume, and Bass - which are A1M (misordered and got A1K previously). So . . . . after installing all the correct pots, as well as changing the 2 caps and 2 resistors (C21, C37, R41, R42), I fired it up. Normal channel works PERFECTLY. Gain, all EQs, Presence, Volume, Depth, all great. However, when I switch to the Overdrive channel, the Overdrive gain control does nothing. The Normal gain control seems to control a small amount of gain but comes through the speakers like a clean channel - is the Normal gain control supposed to act on both channels?

Seems now that the Overdrive gain pot could be bad, even though I just put in a brand new Alpha today



I'm about to give up on this damn thing.

[gorkyporky]

Guys, does anyone know if the Digitech rp1000 works with the JCA50 effects loop? Im thinking of buying one, and this is basicly the only thing thats stoping me.

[shep]

Another progress update:

Got in the correct pots for OD volume, Normal volume, and Bass - which are A1M (misordered and got A1K previously). So . . . . after installing all the correct pots, as well as changing the 2 caps and 2 resistors (C21, C37, R41, R42), I fired it up. Normal channel works PERFECTLY. Gain, all EQs, Presence, Volume, Depth, all great. However, when I switch to the Overdrive channel, the Overdrive gain control does nothing. The Normal gain control seems to control a small amount of gain but comes through the speakers like a clean channel - is the Normal gain control supposed to act on both channels?

Seems now that the Overdrive gain pot could be bad, even though I just put in a brand new Alpha today



I'm about to give up on this damn thing.

on the jca50 and 100 the crunch drive also effects the lead channel. on both amps the crunch and lead channel are mixed together right before the cathode follower. so the lead channel is actually both channels running at the same time. this is not true for the 20 or 22. although the gain for the crunch may effect the lead gain, i know that the two channels do not mix together like in the 50 and 100