Jay wrote:Well, I have in my possesion a JCA 50H! Woohoo! buuuut......it's my buddies amp that won't turn on. Boo. At any rate, I'm going to have it for a while, fix the problem and do the SLO mod to it for him. I'll try to get some pics of the mod stuff for anyone that cares.
Oh hell yeah!
Been real busy gearing up to do the studio we discussed. Your feedback was real helpful on that, Jay. Thanks!
It's looking to be a pretty busy summer for me getting the studio done and I've been working on my pedalboard quite a bit, but hoping to reconnect with the JCA stuff in a couple months. Looking forward to hearing and seeing what you do with the 50 - especially transformer / tube changes!!!
Rock on with the studio, man! I'm finally getting around to getting my basement organized since moving in a year ago. Setting up a workshop/studio/recording station. lol Found my old SM57 and Lexicon interface, so maybe I'll try and record something decent once I get this JCA back up and running.
I'm not sure I'll be doing any transformer swaps with this one, but I'll DEFINITELY be doing the SLO mod. Guy who owns this amp decided he doesn't want to wait if something happens to one of his amps, so he just picked up a 100H on eBay. lol Once the 50H is running, he's going to let me try his 22H for a while, so I'll be messing with stuff to do for those as well. Should be a fun time soon. lol
So, my bud's 50H has suffered a failed PT. I'm trying to figure out with him what route to take in replacement, but I'm trying to get him to go for the Heyboer unit so we can test out some EL34s, 6550s, KT88s, etc. We'll see how it goes.
Other than re-tubing my JCA22H I haven't done much else to it. I am actually a little worried about modding it so I grabbed a cheap Epiphone Valve Jr to practice my modding skills on. So far I have done the JP1 mod, which is easier than shit. Still, it changed the sound of the amp for less than 4$ (the price of the switch). I will eventually get to modding the JCA once my confidence is a little higher. Rock On fellow JCA'ers.
Guitars: Early 90's Ibanez EX Series, Late 80's B.C. Rich Mockingbird, Fairly new Epiphone LP Custom Amp: JCA22H with 4x12 Ibanez Cab No pedals or any real skills...
Jay wrote:So, my bud's 50H has suffered a failed PT. I'm trying to figure out with him what route to take in replacement, but I'm trying to get him to go for the Heyboer unit so we can test out some EL34s, 6550s, KT88s, etc. We'll see how it goes.
Oh... you know this is exactly what I wanted to hear... Sorry for your friend, but hooray for the cause!
racerevlon wrote:Meelo--you don't have to pull the back off the cab--just pull the jack plate, or one of the handles (if they have screws) and shine acheap flashlightin. Work smarter, not harder...
I still haven't done the details mod although I have the components to do it. Is that going to help my situation at all? I think I will have to keep out and see. I have an perfect recognize for it but don't want to start discovery holes because I am afraid I will gap the guarantee should something terrible happen and I need servicing...All this analysis is offering me a headache!
Last edited by Jiranaat on Thu Jun 20, 2013 10:12 pm, edited 1 time in total.
Haven't felt kicked like that since Billy sold his .
Thanks for all your help and enthusiasm, CTN - I am still really enjoying the slope resistor mod!
NOT THE WET NOODLE!!!!!!
lol sorry for hurting your feelings. I sold it to a guy in a sludge band who was craving the soldano sound and he said he loved the way my head looked with the cab (if you remember, I modded both with tan grill cloth and white piping).
It's been a trip being on the Jet City bandwagon and learning about all the fancy shmancy mods people were doing. Felt like an exclusive club when I first got mine and they'd only been around for barely a year at that point. As I recall, I even mentioned their amazing online interactivity with their customer base in a Marketing assignment I was working on for school.
Quick question -- getting ready to sit down and actually mod my 22. The depth mod basically puts a high pass filter in line with the NFB to bring in the bottom end. Should I change the NFB resistor (R42?) value also, or would it be better to leave that alone? I'm hoping less NFB will get me some of the aggression that a Rectifier has.
Promit wrote:Quick question -- getting ready to sit down and actually mod my 22. The depth mod basically puts a high pass filter in line with the NFB to bring in the bottom end. Should I change the NFB resistor (R42?) value also, or would it be better to leave that alone? I'm hoping less NFB will get me some of the aggression that a Rectifier has.
Changing the NFB resistor to a higher value will do just that. Stock is a 47k, I think? Change to a 56k or 68k to bring out more grindiness. Or put it on a toggle switch! Grime loves that stuff!
Well, in the case of JCA50H vs the faulty PT, my buddy has emailed Mr. Doug White himself and explained the situation. Mr. Doug stepped up to the plate and offered to sell us a Mercury Magnetics PT at dealer cost, direct from Mercury. What a fukkin' guy. I also have some cool news that may or may not be allowed to release yet.
In any case, it's cool of JCA to help out like this, and I'll be installing the PT this weekend. MM said their PT will support other power tubes as well. So, I may try some EL34s and 6550s. (although long-term use would require some other internal changes)
If I had KT88s, I would test those too. But, MM says their drop-in piece will accept ALL other octal tubes that can handle the voltage, (EL34s, 6550s, KT88s, KT77, KT66) Keep in mind, I would recommend changing some of the values in the power section to facilitate longevity of the tubes. For now, I'm only gogni to do short bursts to see if there is a decent change. I'll try and get some clips if I can dig out my mic and interface.
Started installing the MM PT into the 50H last night. It's not quite what I would call "drop-in". I've been taking pics, so I'll document it for you guys who are interested in doing ANY kind of trans swap. The mounting feet are a "universal" setup that is um, not really close to the stock location. The CORE dimentions are identical, so the original JCA endbells fit with some spacers added.
I'll finish wiring it tonight, hopefully and try to get my recording gear out. I'll at least give the 6550s and EL34s a try and let you guys know what kind of difference I notice. Then, I'll put up a few posts of the surgery.
I went into my 22 today and unsoldered the NFB wire, just to see what the result would be. I got a Single Recto recently and have been enjoying the Modern setting there, so I figured let's see what happens. I think my Jet City decided to go on a chainsaw killing spree after the surgery. I created a monster
This little 20 watt thing was ripping out a bone crushing sound that said "Recto, you're not the only big dog around here and i'm going to tear your face off". It was massive and powerful and sustained for days. it was also a proper bitch to control and play. There's too much bass for the bottom end to be very tight, so every slight mistake quickly becomes mush. Very unforgiving. And that buzz saw top end gets a bit exhausting after a while, though I think it's actually better than the Recto. I was switching between the two thinking, you know I'm not sure which one I'd prefer. You'd never know the JC had a power deficiency.
I think the depth mod will give me the low end punch I'm craving, without being as crazy unforgiving. I'm pondering what to do with the NFB as well; I might give it a Modern switch to put another resistor in series. What's the correct spec for resistors to go into this amp? 1/2 watt carbon film?
Well, the Rectos on their modern setting actually disconnect the NFB, so if you disconnect the NFB on the JCA, it will take on a lot of that Recto "personality"
Hope some of you JCA experts can offer some advice. RE:JCA100H I traded this amp off and quickly got it back from the guy telling me it hums like crazy and he was told it was a known transformer issue. Upon getting the thing hooked back up at home, I power it up in search of this hum (thought the guy was full of it). I had never heard any hum out of it before. As it turns out, there's no hum...well not at reasonable volume and gain settings, but with the gain approaching 7 and beyond plus volumes most people wouldn't need, there it was. Not a hiss mind you, a bonafide hum. Sometimes I need to coax it out of the amp with a series of chugs or something and then just stop to get it to happen. It goes away when turning guitar volume down (it's not the guitar...same thing happens with every guitar and none do it through my other amp). No effects used and tried it in different locations away from other electronics in the house and it doesn't change. Tried getting away from the amp and going in another room. Also tried different new preamp tubes and other cables with no change. Any chance this is a power tube issue? Don't happen to have a spare set at the moment to try. I did open it up and reset the bias using a bias probe to see if it had drifted and cooling the setting helps a little but I get the feeling it's just due to the loss of some output biased cold. Just curious if anyone that knows way more than I do about troubleshooting this sort of thing has any ideas. Thanks in advance guys.
Hums in high-gain amps at high gain settings and loud volumes aren't unheard of. After I get the one on my bench all squared away, I'll check to see if it does the same thing.
Not sure if the 100H has a known transformer problem, but the 50H I'm repairing has suffered a PT meltdown.
Jay wrote:Hums in high-gain amps at high gain settings and loud volumes aren't unheard of. After I get the one on my bench all squared away, I'll check to see if it does the same thing.
Not sure if the 100H has a known transformer problem, but the 50H I'm repairing has suffered a PT meltdown.
As soon as he mentioned his "tech" saying it was a "known transformer issue" I searched for info and found nothing. I also run a Mesa Single Rec and under the same conditions it doesn't do this but.....if I kick in the solo function and it's loud enough, it will. When I say at volumes most people wouldn't need, I'm talking gig with no PA volume. Other than this, the amp acts fine.
Hmm. Can someone hunt down a good knob on Mouser that is a pretty close match to the stock? I'm skimming through here but not really seeing anything. My depth knob is just a pot shaft right now.
Promit wrote:Hmm. Can someone hunt down a good knob on Mouser that is a pretty close match to the stock? I'm skimming through here but not really seeing anything. My depth knob is just a pot shaft right now.
Get the Dunlop style ones from here http://www.tubesandmore.com/products/P-K345 if you need one with a set screw to match. If you're using a pot that is a knurled shaft like the original ones PM your address and I'll send you some OEM ones...I have a few hundred laying around.
Promit wrote:Hmm. Can someone hunt down a good knob on Mouser that is a pretty close match to the stock? I'm skimming through here but not really seeing anything. My depth knob is just a pot shaft right now.
Get the Dunlop style ones from here http://www.tubesandmore.com/products/P-K345 if you need one with a set screw to match. If you're using a pot that is a knurled shaft like the original ones PM your address and I'll send you some OEM ones...I have a few hundred laying around.
Brian
Righteous dude, right here!
Is that a JCA20 or 22 in your avatar? I dig the faceplates. Like a metalface Marshall. Sexy.
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