Members JacieFB Posted October 29, 2008 Members Share Posted October 29, 2008 So you may or probably won't remember me complaining about my Marshall JCM 900 a few weeks ago. I didn't like the tone and the volume knob for the high gain channel was sick. Well, turns out I've been loving the tone lately. And some contact cleaner helped the volume pot. However, now I fear that the input jack is f'ed. Is this something I can or should change myself? Thanks in advance! Link to comment Share on other sites More sharing options...
Members Bryan316 Posted October 29, 2008 Members Share Posted October 29, 2008 JCM 900's sound horrible for bass guitar. Link to comment Share on other sites More sharing options...
Moderators Kindness Posted October 29, 2008 Moderators Share Posted October 29, 2008 If you wonder whether you can, you probably shouldn't. However, replacing a jack is a very simple task for someone that knows what they're doing. Link to comment Share on other sites More sharing options...
Members JacieFB Posted October 29, 2008 Author Members Share Posted October 29, 2008 If you wonder whether you can, you probably shouldn't. However, replacing a jack is a very simple task for someone that knows what they're doing. I've replaced many jacks on various guitars and basses. Does this qualify me as someone that knows what he's doing? *crosses fingers* Link to comment Share on other sites More sharing options...
Moderators Kindness Posted October 29, 2008 Moderators Share Posted October 29, 2008 I've replaced many jacks on various guitars and basses. Does this qualify me as someone that knows what he's doing? *crosses fingers* Basses and guitars don't have caps storing hundreds of volts waiting to kill you. Your amp does. If you know how to drain the caps and make your amp safe to work on, go for it. Because you are asking, I would say don't. If I were standing over your shoulder, I'd be less cautious with my advice, but I'm not going to give you the okay to do something that could be fatal. Link to comment Share on other sites More sharing options...
Members bigmac9137 Posted October 29, 2008 Members Share Posted October 29, 2008 you dont hve to place it....open it up and tighten to input jack, it might be loose. Im sure you have done contact cleaner on the input jack too?...it probably can be done, but if it needs to be replaced then you should probably have a pro do it Link to comment Share on other sites More sharing options...
Members JacieFB Posted October 29, 2008 Author Members Share Posted October 29, 2008 Basses and guitars don't have caps storing hundreds of volts waiting to kill you. Your amp does. If you know how to drain the caps and make your amp safe to work on, go for it. Because you are asking, I would say don't. If I were standing over your shoulder, I'd be less cautious with my advice, but I'm not going to give you the okay to do something that could be fatal. Okay, this is the info I was looking for. Thanks, man. I'll not tackle it myself. Link to comment Share on other sites More sharing options...
Members Guttermouth Posted October 29, 2008 Members Share Posted October 29, 2008 what exactly is going on with the input jack ? is it intermittent ? Link to comment Share on other sites More sharing options...
Members JacieFB Posted October 29, 2008 Author Members Share Posted October 29, 2008 what exactly is going on with the input jack ? is it intermittent ? The sound cuts out every now and then. When that happens it sounds like a cable is going bad. I swap out cables and try the same cables on different amps. Same thing happens regardless of cable on the Marshall. I can't get it to repeat on any other amps. I tried tightening the plastic retainer nut on the input jack on the Marshall and it seemed to help. I'm not 100% sure it's the jack. Since it's a simple fix on a guitar or bass, usually, I thought it might be a place to start the discussion. Link to comment Share on other sites More sharing options...
Members prosigna Posted October 29, 2008 Members Share Posted October 29, 2008 you dont hve to place it....open it up and tighten to input jack, it might be loose. Im sure you have done contact cleaner on the input jack too?...it probably can be done, but if it needs to be replaced then you should probably have a pro do it Please do not open up a tube amplifier without first knowing what things in there can kill you. Link to comment Share on other sites More sharing options...
Members Guttermouth Posted October 29, 2008 Members Share Posted October 29, 2008 The sound cuts out every now and then. When that happens it sounds like a cable is going bad. I swap out cables and try the same cables on different amps. Same thing happens regardless of cable on the Marshall. I can't get it to repeat on any other amps. I tried tightening the plastic retainer nut on the input jack on the Marshall and it seemed to help. I'm not 100% sure it's the jack. Since it's a simple fix on a guitar or bass, usually, I thought it might be a place to start the discussion. sounds like it's time to take it to the shop mang. Link to comment Share on other sites More sharing options...
Members squish_man24 Posted October 29, 2008 Members Share Posted October 29, 2008 JCM 900's sound horrible for bass guitar. The JCM800 on the other hand: Listen to Firebreater at around 1:31 Link to comment Share on other sites More sharing options...
Members mrcrow Posted October 29, 2008 Members Share Posted October 29, 2008 If you wonder whether you can, you probably shouldn't. However, replacing a jack is a very simple task for someone that knows what they're doing. +1 have a good look at the casing access...that would be i think the hardest part of the deal...getting into the jack Link to comment Share on other sites More sharing options...
Members JacieFB Posted October 29, 2008 Author Members Share Posted October 29, 2008 sounds like it's time to take it to the shop mang. Fye!!! I'm going to take your advice, though. Thanks, folks. Link to comment Share on other sites More sharing options...
Members Cliff Fiscal Posted October 29, 2008 Members Share Posted October 29, 2008 Discharging the caps isn't as hard as everyone makes it sound....but it has the potential to be dangerous if you just start poking around in there with a screwdriver. Plus, you'll always want to check the caps to make sure they're drained before you start repairing things. Link to comment Share on other sites More sharing options...
Moderators Kindness Posted October 29, 2008 Moderators Share Posted October 29, 2008 Discharging the caps isn't as hard as everyone makes it sound....but it has the potential to be dangerous if you just start poking around in there with a screwdriver.Plus, you'll always want to check the caps to make sure they're drained before you start repairing things. No one said it's hard. The problem is a mistake can kill you. Link to comment Share on other sites More sharing options...
Members Cliff Fiscal Posted October 29, 2008 Members Share Posted October 29, 2008 No one said it's hard. The problem is a mistake can kill you. I was researching it a while back and I actually stopped pursuing it...because everyone spooked me so bad. When really, you just have to be careful, know a little info.....and go through a few easy steps. Link to comment Share on other sites More sharing options...
Members JacieFB Posted October 29, 2008 Author Members Share Posted October 29, 2008 This thread is like a PSA! Link to comment Share on other sites More sharing options...
Members prosigna Posted October 29, 2008 Members Share Posted October 29, 2008 I was researching it a while back and I actually stopped pursuing it...because everyone spooked me so bad.When really, you just have to be careful, know a little info.....and go through a few easy steps. You are absolutely correct! Here are the wrong steps: 1. Find a screwdriver2. Open your amp3. Stick your hand inside the amp4. Get hit with 300 volts DC5. Have your heart stop4. Die These would be the correct steps (much like you stated): 1. STOP2. Be Careful3. Get some info (maybe just a bit more than "a little")4. Be Careful5. Discharge the caps properly6. Fix the amp7. Live Link to comment Share on other sites More sharing options...
Members Cliff Fiscal Posted October 29, 2008 Members Share Posted October 29, 2008 I personally like the insulated alligator clips from ground to pin 1 of V1 method.....takes longer....but works well. I end up touching each cap after it's drained anyway....then check them with a DMM. Again, be careful....don't do anything unless you know your stuff. Link to comment Share on other sites More sharing options...
Members Guttermouth Posted October 29, 2008 Members Share Posted October 29, 2008 Fye!!! I'm going to take your advice, though. Thanks, folks. just as an aside... i don't know if you remember but, a while back i purchased a load of russian jcm800 clones made by novik for gibson and marketed under the "redbear" name. alltogether - i had enough parts to put together 6 amps.gibson had partially disassembled them in order to repair customer's amps that were under warranty. at any rate, i've worked on enough amps at this point that i could build an 800 in my sleep but these amps had some particularly strange russian filter caps in them. they're called "milk bottle" caps because they look like miniature milk cans and they have the positive lead off the dielectric on their exterior cover ( the exact opposite of the filters you see in every other amplifier). keep in mind that every one of these amps,after they were biased, had between 488 and 492 volts on the caps.the second to last one of these amps just happened to have a shorted power tube when i fired it up the first time and it popped the ht fuse. i was in a hurry and when i unscrewed the fuse holder the retaining ring on it broke in half. i unplugged the amp, grabbed a pair of lineman's pliers that i use to work on live amps and replaced the fuse holder. as i was snugging the nut up on the replacement my hand slipped and the pliers nose grounded the hot lead from the fuse holder to the chassis through my hand. as i awoke i was falling backwards and this high pitched monotone squeal was coming from my mouth.i caught myself with the edge of my bench to keep from hitting the floor. it felt like someone had just hit me with a sledgehammer and i was shaking violently and had no idea where i was. i turned everything off, grabbed my cigarettes and went to my living room. it took a pack of smokes, and almost two bottles of gatorade to make the shaking stop and i had a migraine for days afterwards. i can assure you - you don't wanna be {censored}ing around with it. Link to comment Share on other sites More sharing options...
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