rikkinroll
Rookie Solder Flinger
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Post by rikkinroll on Jun 27, 2005 15:25:17 GMT -5
Once in awhile, actually more and more, my amp will go from regular playing volume to FULL volume all by itself. If I tap the input, it goes back to normal for a bit, but them it does it again. You can imagine the faces of the crowd when they have the skin blown off their faces!
What causes this, and how much can I figure to spend? One guy said it might just be a faulty input, another said it's the power transformer. Please help!
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Post by erikh on Jun 28, 2005 8:57:02 GMT -5
I don't think the power transformer would do that. If it was the tranny, you'd probably hear a drop in volume, not full blown. It could be the input and it could be the master volume pot going open. When was the last time the pots were cleaned? Get it to a reputable repair shop for evaluation. They'll do much better with the amp in front of them.  Personally, I see nothing wrong with a JCM800 at full volume but for the sake of the patrons, it needs to be taken care of. ;D |
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wixedmords
Rookie Solder Flinger
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Post by wixedmords on Jun 28, 2005 9:52:08 GMT -5
Once in awhile, actually more and more, my amp will go from regular playing volume to FULL volume all by itself. If I tap the input, it goes back to normal for a bit, but them it does it again. You can imagine the faces of the crowd when they have the skin blown off their faces! What causes this, and how much can I figure to spend? One guy said it might just be a faulty input, another said it's the power transformer. Please help! Try cleaning the effects loop jacks and input jack with electrical contact cleaner. You can get it Radio Shack, or other electrical supply places. |
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Post by RollnROCK89i on Jun 29, 2005 23:41:03 GMT -5
Personally, I see nothing wrong with a JCM800 at full volume but for the sake of the patrons, it needs to be taken care of. ;D lol |
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jamie
Apprentice Shielder
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Post by jamie on Jul 6, 2005 9:42:31 GMT -5
If you take it to a repair shop, only let them fix it if you can be present while they do the work. This way you can learn a little about what needs to be done. The tech will have no option but to be honest with you. Otherwise they could charge you for parts that arent even needed or installed.
You could even chat with the tech and build rapport. If not much work needs to be done the tech may charge you alot less if you have built a little friendship.
Just a tip, i wish someone would have told me that.
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Post by RandomHero on Jul 7, 2005 0:14:42 GMT -5
I feel at a loss for not knowing much about the JCM800s. Can someone describe the sound for me? From what I understand, this amp has a lot more riding on it than Marshall's nice manuscript nameplate, and I'm looking for a good tube amp upgrade for gigging and jamming. What sorts of packages does it come in? Combo, stack? How's the clean, does it do a good slightly overdriven sound or does it sound squashy and farty? How's the all-out gainiac setting?
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Post by erikh on Jul 7, 2005 9:04:01 GMT -5
I feel at a loss for not knowing much about the JCM800s. Can someone describe the sound for me? From what I understand, this amp has a lot more riding on it than Marshall's nice manuscript nameplate, and I'm looking for a good tube amp upgrade for gigging and jamming. What sorts of packages does it come in? Combo, stack? How's the clean, does it do a good slightly overdriven sound or does it sound squashy and farty? How's the all-out gainiac setting? They pretty much defined the 80's metal scene. They're high gain but nowhere near as high gain as what is out there now. They "came" in a combo version as well as the head version, 50 or 100 watts (a few models did anyway). Marshall has recently reissued the head version only of the 2203 with an effects loop added. The original didn't have one. The 50 watt version would be good for gigging, even in the combo package if you can find one. If I had extra cash laying around, I'd be going on a mad hunt for an all original 2203 head and 4104 combo, and a mad hunt it would be because a lot were modified (extra gain stage, effects loop added, God knows what else). There's actually several JCM800 models. Here's an excerpt from Dr. Tube's web site: "The Super Leads (1959 & 1987) were issued as heads only, while the Master Volumes (2203 & 2204) and the new Split Channels (2205 & 2210) were also issued as combo's (4103, 4104, 4210, 4211 & 4212)." |
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rikkinroll
Rookie Solder Flinger
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Post by rikkinroll on Jul 8, 2005 9:55:25 GMT -5
The one in question here is a 2210 head from '87. It has an effects loop and a direct out with a volume control, neither of which I use. The clean setting is outstanding, actually the only channel I usually use. I run effects instead of the overdrive channel, which sounds great, but not quite enough balls for what we play. I've had to fix the reverb twice, as the springs tend to pop off their mounts.
If this amp cannot be fixed, I will search high and low to find another. Truly one of the best amps ever made.
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Post by Trey on Jul 9, 2005 8:27:31 GMT -5
If you take it to a repair shop, only let them fix it if you can be present while they do the work. This way you can learn a little about what needs to be done. The tech will have no option but to be honest with you. Otherwise they could charge you for parts that arent even needed or installed. You could even chat with the tech and build rapport. If not much work needs to be done the tech may charge you alot less if you have built a little friendship. Just a tip, i wish someone would have told me that. Man, you need to find a new tech. I drop my amps off to my tech without a worry in the world of being overcharged or shafted in any way, shape or form. I think it's more important that you find a good tech, rather than constently look over the shoulder and generally hassle an average or subpar tech. If I were an amp tech, I wouldn't be open to someone looking over my shoulder as I fixed thier amp because it would be a hassle and would probably turn an easy 15 min job into a 3 hour long question and answer session... |
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Post by UnklMickey on Jul 13, 2005 13:21:24 GMT -5
i suspect that tapping the input is rattling other stuff as well, so it's not necessarily the input that is intermittent. If you look at the way the volume and master volume controls are implemented in the circuit, they are adjustable voltage dividers feeding the grid of the next tube. If the ground connection of the control is open or the control is cracked, then you no longer have a voltage divider -- just a resistor in series with the next grid. since a grid has a very high impedance, it wont load down the control at all. It's like you just turned up the control to max.
A decent tech will be able determine which control it is and whether it is a crack in the control or an intermittent connection between the control and ground.
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