Members Edge11 Posted December 2, 2012 Author Members Share Posted December 2, 2012 Originally Posted by IBDBB yes, thank you, don't know how i missed that... YOur mods are very easy to read and seem pretty easy.Would you care to list out the dues/vh4 mods? Then you would never be able to learn to read a schematic. It's easy, I believe in you. Link to comment Share on other sites More sharing options...
Members macheted01 Posted December 12, 2012 Members Share Posted December 12, 2012 Hey All, I've had my eye on one of these, since the day they came out. Currently, one of my band members is an amp and guitar tech and will be doing any work that I need done. The only other tube amp that I have owned was my Ampeg V2 and matching 4x12, which I recently sold. It was just too much and too big. I am thinking I will just upgrade the tubes. Would also like to consider putting in an effects loop. After reading through this thread a bit, I was wondering what you guys decided that may have been the best choice to do so? I seen the Zero Loss FX Loop kit from Metroamp and one other choice on this thread, so far. I have not completely made it through the whole thread yet. As I said, I have a guy to do the work, I would just like to grab as much info ahead of time, as I can. I know there is the JCA22H and also the JCA20HV that is out now, but at that price point, I would maybe consider a different amp all together. If I was gonna go that far, I was thinking, I might as well throw another $200.00 in and go for something like the Hughes & Kettner Tubemeister 18, unless I am missing something here. I just like the price point that I can get into the JCA20H for and get the work done for free other than parts. He may even have a different approach other than what is listed, I dont know. Looking forward to hearing your thoughts. Link to comment Share on other sites More sharing options...
Members stilllifer Posted December 13, 2012 Members Share Posted December 13, 2012 Originally Posted by macheted01 Hey All,I've had my eye on one of these, since the day they came out. Currently, one of my band members is an amp and guitar tech and will be doing any work that I need done. The only other tube amp that I have owned was my Ampeg V2 and matching 4x12, which I recently sold. It was just too much and too big.I am thinking I will just upgrade the tubes. Would also like to consider putting in an effects loop. After reading through this thread a bit, I was wondering what you guys decided that may have been the best choice to do so? I seen the Zero Loss FX Loop kit from Metroamp and one other choice on this thread, so far. I have not completely made it through the whole thread yet. As I said, I have a guy to do the work, I would just like to grab as much info ahead of time, as I can.I know there is the JCA22H and also the JCA20HV that is out now, but at that price point, I would maybe consider a different amp all together. If I was gonna go that far, I was thinking, I might as well throw another $200.00 in and go for something like the Hughes & Kettner Tubemeister 18, unless I am missing something here.I just like the price point that I can get into the JCA20H for and get the work done for free other than parts. He may even have a different approach other than what is listed, I dont know. Looking forward to hearing your thoughts. Hey. Well since this is a JCA20H Mod thread, we are possibly a tad biased!!! Regardless, I don't think you can go wrong with the JCA20H or 22H, especially since you can get the mods done for nothing - best price of all!!! The Tubemeister is pretty cool, especially with its' built in power soak and DI for recording but honestly, I found it was just OK, even cranked into a 4x12 - found it very loose sounding (could be stock tubes, no mods etc) but wasn't blown away. I think my JCA20H is way better, actually slays the H&K - much tighter sounding even before any mods done. You will def want to swap out the tubes IMO (some guys like the stock tubes, YMMV) but I hated them. I put in vintage Mullard EL-84's and various 12AX7's and 7025 and it is an amazing difference in tone. The mods on first couple of pages of this thread are great - the Super Sucker Punch and Depth mods I've done have made a world of difference. I now run this head with the preamp gain down just to breakup into my Carl Martin Plexitone pedal and I've got Marshall tones from JMP to full-out JCM800 into my 2x12. You won't regret it man!Cheers! Geoff Link to comment Share on other sites More sharing options...
Members macheted01 Posted December 13, 2012 Members Share Posted December 13, 2012 Thanks Geoff for the reassurance, because I just bought a JCA20H through ebay for $203.00 with shipping. No mods done, just re-tubed with JJ EL84 (2) power tubes and JJ 83S (3) preamp tubes. Cant wait to get it. When it gets here, I will decide where I need to go with. Pretty sure I will be looking to put in the FX Loop. For those here with experience with the Loop, i was wondering what the best approach was. Currently using my backup amp to the Ampeg V2, which is a Crate Powerblock. Soon to be my backup to the JCA20H, if things work out as planned. I used to dump my effect chain straight in to the front of my V2, but really found it lacking for the obvious effects. With my Powerblock having an FX Loop, proves to be a big improvement. So, in any case, I am leaning towards getting the loop in first. Link to comment Share on other sites More sharing options...
Members Jead72 Posted December 22, 2012 Members Share Posted December 22, 2012 YIKES! Not really a mod question but a cry for HELP! I have 2 jca20h's #1 I did the depth mod and added a choke to. #2 I just got and it seemed to be working fine (besides the intermittent blue power led). I did the depth mod for it using a 250k cts audio pot instead of a 500k. I started the amp up and the volume was maybe about 1/4 to 1/3 of what it should have been and then after a few minutes it kicked in to where it should be. It then, accompanied by a bit of static, went back to 1/4 or 1/3 volume. I could tell that the depth was working. I have known good tubes. I'm at a loss as to what has happened. I went and undid the mod and had the same lack of output, re-soldered the mod back in and - same. I'm not afraid to troubleshoot the amp but I really have no idea where to begin with it. I fear I may have a sketchy OT. Can anyone lend their thoughts and experience? Currently bummed out, Jay ps: the output is really broken up and staticy and seems to have something of an oscillation quality. Sounds like the gain is way up when it's not. Every once in a while the static disappears but no further change....... Link to comment Share on other sites More sharing options...
Members Edge11 Posted December 28, 2012 Author Members Share Posted December 28, 2012 possible bad tubes, (recheck them if you can) bad solder joints, broken pots you name it. look for visual signs, then whip out the v meter. I'll post up a good debugging workflow when i get up in the afternoon. Link to comment Share on other sites More sharing options...
Members Jead72 Posted December 29, 2012 Members Share Posted December 29, 2012 Issue solved. As it turns out there must have been a fair amount of solder on the 8 ohm output I soldered the NFB from the resonance pot to. All I did was reheat the tab and add the wire but a blob somehow managed to bridge the contacts below where I was working so it was really difficult to spot. An easy fix but really irritating to find. Now if I could only eliminate the hum on these amps I'd be happy. Why no DC filament??? I have a couple mini hum balance pots and it looks like if I stuck them in with r10 and r11 and got a ground somewhere, that might help. Not exactly sure on that but it seems a reasonable idea. Any thoughts on that or other ways to reduce the hum? Link to comment Share on other sites More sharing options...
Members macheted01 Posted January 2, 2013 Members Share Posted January 2, 2013 Alright, I have my JCA20H and loving it. I might go for a little more clean headroom, but I still am more interested in the FX Loop. Have not heard back from anybody on it. Would like to know what the best approach for the loop was? Thanks. Link to comment Share on other sites More sharing options...
Members Jead72 Posted January 24, 2013 Members Share Posted January 24, 2013 I built a couple enclosures for the kids. " rel="nofollow">http://i250.photobucket.com/albums/gg270/Jead72/2013-01-19005.jpg[/img] Link to comment Share on other sites More sharing options...
Members brunoserrano86 Posted February 5, 2013 Members Share Posted February 5, 2013 Hello. I want to make an active loop to my JCA20H and I want to know if the power transformer have enough power to supply 6.3V to the heaters of 2 new 12AX7 Anyone knows this? Sorry about my english, I'm Brazilian. Link to comment Share on other sites More sharing options...
Members Soulcrusher_X Posted February 12, 2013 Members Share Posted February 12, 2013 brunoserrano86 wrote: Hello. I want to make an active loop to my JCA20H and I want to know if the power transformer have enough power to supply 6.3V to the heaters of 2 new 12AX7 Anyone knows this? Sorry about my english, I'm Brazilian. Is there a sticker on the side of the power transformer? I thought I read a while back that it should be able to supply another tube. Why would you need two 12AX7s? Link to comment Share on other sites More sharing options...
Members Soulcrusher_X Posted February 12, 2013 Members Share Posted February 12, 2013 macheted01 wrote: Alright, I have my JCA20H and loving it. I might go for a little more clean headroom, but I still am more interested in the FX Loop. Have not heard back from anybody on it. Would like to know what the best approach for the loop was? Thanks. What kind of loop do you want? Solid State or Tube-buffered? Solid State kit from Mojotone apparently works really well, and if I'm correct, is the same one on the 20HV. A guy I was helping mod his 20H on the SeymourDuncan forum said he installed the mojotone kit fairly easily. Link to comment Share on other sites More sharing options...
Members audiosalvage64 Posted February 26, 2013 Members Share Posted February 26, 2013 While checking ground to OT red wire, I get 500 volts. Then switching to mA, from red to blue or brown I get 0. If I change to Amperes setting I get .4, what gives? Link to comment Share on other sites More sharing options...
Members Soulcrusher_X Posted March 1, 2013 Members Share Posted March 1, 2013 audiosalvage64 wrote: While checking ground to OT red wire, I get 500 volts. Then switching to mA, from red to blue or brown I get 0. If I change to Amperes setting I get .4, what gives? Happened to a buddy of mine. Tried to bias his tubes and kept getting weird readings. Turns out his meter was no good. Didn't blow the fuse in yours, by chance? Link to comment Share on other sites More sharing options...
Members malhomme Posted April 4, 2013 Members Share Posted April 4, 2013 Hi to allI am (or rather hoped) to be a new member of the community. I bought second hand a JC20H received yesterday. I have the 2x12 baffle on it's way too. I am a french guitar player and have a few clips there My soundcloud page Unfortunately, not exactly what I expected from the videos and sound clips here... The amp is making a loud buzz making it impossible to use clean, and it produces a weird clipping noise used solo with gain past 12 o' clock. My first take is I may have to change all tubes for a start, they may have been damaged in the delivery process (the amp was badly protected).I am very interested in all mods alound here. Something lie the brown sound is appealing to me. AS well as a sort o two channel mod with clean channel. And as well an effect loop. All these make quite a lot... I will have to choose I guess.... I have yet to finish reading all 64 pages of the topic... Link to comment Share on other sites More sharing options...
Members maa139 Posted August 4, 2013 Members Share Posted August 4, 2013 I put a metro fx loop in mine. Very simple install, dialed in the volume via the trimpot on the loop board and works like a champ. I followed the instructions at the bottom of this thread and had no problems.http://forum.metroamp.com/viewtopic.php?f=7&t=32582 Link to comment Share on other sites More sharing options...
Members knel8025 Posted September 3, 2013 Members Share Posted September 3, 2013 Quick question regarding the clean channel mod on the first page for anyone who still follows this thread:-Where it says "You then bypass the original 1m resistor r53 with a 250pf capacitor", is this simply putting a cap in parallel with R53 or "piggybacking" the cap on to it? Or should this resistor be removed entirely? Thanks for any input. Link to comment Share on other sites More sharing options...
Members vintonalan Posted September 5, 2013 Members Share Posted September 5, 2013 I did this mod with a 500K Bourns pot out of a cry baby volume pedal. Worked well! Gave some low end balls to the amp it was missing. And I agree with something I read along the way, just lift the yellow wire off the output txformer and go to one side of the pot with cap and take the other side back to the 16 ohm jack +.2 wire mod + one hole drilling. I happened to mount mine on the back panel just to the left of the speaker outs. Link to comment Share on other sites More sharing options...
Members rjonsolo1 Posted September 30, 2013 Members Share Posted September 30, 2013 Just listened to you sound clips. Is that stock and if so, what did you do to get that much gain. Mine is kinda mushy. More vintage sounding. But I'm running through a 412. Thanks Link to comment Share on other sites More sharing options...
Members mrbadwr3nch Posted December 7, 2013 Members Share Posted December 7, 2013 Howdy. I'm new here. I've got a jca20h and I've done a few mods to it including; choke mod, depth pot mod, super sucker punch with a spst to switch c23 (swapped to a 250pf) in and out (I call it a dark switch). This little head now rivals some of the best i've heard. However, I want do this clean channel mod and set it up with a footswitch (and move the "dark switch" to a footswitch). If it's not to much trouble could someone direct me to a parts list, a more in-depth guide and a photo or two of the mod. Also, I see 3 spst switches and don't quite understand the need for all of them. Please help! Link to comment Share on other sites More sharing options...
Members Graunke Posted December 26, 2013 Members Share Posted December 26, 2013 I'd like to do the 'depth' mod to my 22H, is the schematic similar, or does someone have one they can share? I tried to skim through all 65 pages, but did not see it. Only the one for the 20H Link to comment Share on other sites More sharing options...
Members diyfortes Posted January 9, 2014 Members Share Posted January 9, 2014 Hello everyone, I'm new here.I have an Jca20h, a big amp, but he has a problem that I can not solve, I appreciate if someone can help me.....Anyone know what may cause the burning of R3 resistor? ***Problem solved, short on R7 Link to comment Share on other sites More sharing options...
Members jhadl Posted January 18, 2014 Members Share Posted January 18, 2014 Does anyone know what mods Hovercraft does to the JCA20H to make it a Dwarvenaut 20?I'm looking at a gut shot and it seem like there is some sort of double version of the depth mod and then a voicing switch added to the input jack.. Link to comment Share on other sites More sharing options...
Members jhadl Posted January 26, 2014 Members Share Posted January 26, 2014 Here is the stock gut shot and here is a modded one Link to comment Share on other sites More sharing options...
Members jessepage1989 Posted June 7, 2014 Members Share Posted June 7, 2014 Damn I jump back on this thread because I want to try some new mods and all the schematics and pics are gone via broken links. I'm bummed Link to comment Share on other sites More sharing options...
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