'82 Marshall JCM 800 4010 combo blowing fuses

  • Thread starter Thread starter BluesManRocker
  • Start date Start date
The guy at Elderly was like, I'm sorry, no, we don't do inhouse amp repair here. (pause) (and I mean a listening for me to veer off into another direction pause, so he doesn't have to go on, sort of pause,,)

and then he says,, ok, yeah, we have this other guy too. Hold on...
 
As soon as he says his name, I was like YES!!! THAT'S THE GUY. I talked to this guy like 5-6 years ago and sorta pre-qualified him. He says give him a call in a month or so, and we'll see what we can do!
 
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I had a great discussion with this amp tech, he's my kind of guy. He's worked on plenty of JCM 800's before, and we spoke for a half hour, and I ended up telling him about the cool magnetic attenuation tech, that Brad Paisley shows off so well. Him and Fluxtone and youtube, and it's amazing natural attenuation.

And since my amp's bias is not too hot, it should not hurt the amp, but if it start blowing fuses, then probably stop using it. But I feel comfortable using the amp with new tubes at this point. But I don't know if it will stay running when I turn it up, that remains left to be seen. I have a complete fresh set of preamp and power-tubes, so I am excited about trying out the amp again.

Lets hope I don't start blowing fuses again...

 
NOW I would really question my sanity.

HMM, have the amp to that tech, or Risk brand new expensive tubes in a crap shoot before getting the amp sorted out 100%
 
chilipeppermaniac said:
NOW I would really question my sanity.

HMM, have the amp to that tech, or Risk brand new expensive tubes in a crap shoot before getting the amp sorted out 100%
Click to expand...
I hear that, but I have SIX,,, I SAID SIX,,, ,,, pause,, eh hemmm,, years of not using this amp. (chuckles at myself) I have already waited for what seems like several lifetimes for this moment. There is only so much patience and idealism left in the world my friend, sometimes we must grasp the moment for what it's worth and let that bell ring.

Here's the plan so far. Let me know what you think.

If it does not blow after turning it up, then I'm in and I'm playing the amp. But if it blues a fuse under brand new tubes, then flewey on that, I'll wait until the amp tech makes it right before I try playing out of it again. You see, the last time after 5 years of no playing my only tube amp, all I had to do was buy a full set of tubes and the right fuses and it started working great. Super loud, never blew fuses, played 3 nights a week for 2 hours a night and sounded pretty good.

Then I started diagnosing the amp, meaning I took it out of the combo, and so I was moving it around more, and I moved it once while it was unplugged, and without knowing it, the speaker cable just got disconnected. So when I turned on the amp, it blew a fuse, blue the power tube. So that's when I discovered that my amp's bias range was out of range, and needs correcting.
 
The bias range is not too hot or too cold for EL34's, so the tubes should be safe. If I'm essentially putting my amp back to the condition it was a month ago, then I can rock tonight, and rock hard. But I only get up to MV 3-3.5. I'm own my house, but it's in the city. I need some dabs, and then lets do this.
 
Thank you COL. Now Blues, if Col says the place does right by you, he isn't blowing smoke up your skirt.

Good luck and please get it fixed right and let us know it is 100% ready to play.
 
chilipeppermaniac said:
NOW I would really question my sanity.

HMM, have the amp to that tech, or Risk brand new expensive tubes in a crap shoot before getting the amp sorted out 100%
Click to expand...

I got test I do to make sure everything is good.
Then I put in the tubes last.
That way I don't fry any tubes by accident hopefully.
But really it only takes about 15 minutes to test all that stuff.

I test the speakers too usually.
 
BluesManRocker said:
The bias range is not too hot or too cold for EL34's, so the tubes should be safe. If I'm essentially putting my amp back to the condition it was a month ago, then I can rock tonight, and rock hard. But I only get up to MV 3-3.5. I'm own my house, but it's in the city. I need some dabs, and then lets do this.
Click to expand...

I told you not to play that amp. The bias is way off.
That's way too hot for EL34s.
 
BluesManRocker said:
I had a great discussion with this amp tech, he's my kind of guy. He's worked on plenty of JCM 800's before, and we spoke for a half hour, and I ended up telling him about the cool magnetic attenuation tech, that Brad Paisley shows off so well. Him and Fluxtone and youtube, and it's amazing natural attenuation.

And since my amp's bias is not too hot, it should not hurt the amp, but if it start blowing fuses, then probably stop using it. But I feel comfortable using the amp with new tubes at this point. But I don't know if it will stay running when I turn it up, that remains left to be seen. I have a complete fresh set of preamp and power-tubes, so I am excited about trying out the amp again.

Lets hope I don't start blowing fuses again...

Click to expand...

I told you the bias is wrong.
Are you just going to blow up the tubes again?

I really can't do much good on this if you keep crashing it into the dirt.

I told you the bias is supposed to be -42 volts DC.
I told you how to fix that but you didn't fix it.

Bad Idea.
 
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Amp Mad Scientist said:
I told you not to play that amp. The bias is way off.
That's way too hot for EL34s.
Click to expand...
Sorry, I did not really catch that part. I thought it was in acceptable range, close enough, but not at the best bias spot. It sounded great with the new tubes in there. Recall, a month ago, all I did, to get this amp going again, was put in a new set of tubes, and fuses. And I played on that for lets say 3 weeks every other night for 2-3 hours a night. Loud. Seemed like it was fine but could use better tubes and of course, better bias range and adjustment.

I thought the range was the bigger trouble, not the actual adjustment. Wow, the telefunkin's sounded great tho. A pair in the power section, and one in the lead spot at V1. Mullards at V2 and V3, all new production but the Telefunkins are twice as costly. It's the first time I did not have to turn down my tone knob. The tonal spectrum was rich and notched down to a lovely level with ZERO piercing top end.

For the first time ever, I set the tone on the bridge pickup from 3/4 to full open, and it did not get too harsh!!! The tones was just beautiful, and it felt sexy, it was so good. hehe
 
Ohhhhh, I thought -42 was just a new test target, like, lets start there and after you have that set there, tell me what it sounds like, if you have a scope, it can be dialed in better, but sorry, I did not realize that 42 was the correct setting, and 35.5 was a bad or troublesome setting. I just wanted the range to change so we could set it better for tone, not to set it to proper setting. You have helped me so much, I just accept what you say with my limited understanding of what you fully mean.
 
BluesManRocker said:
Sorry, I did not really catch that part. I thought it was in acceptable range, close enough, but not at the best bias spot. It sounded great with the new tubes in there. Recall, a month ago, all I did, to get this amp going again, was put in a new set of tubes, and fuses. And I played on that for lets say 3 weeks every other night for 2-3 hours a night. Loud. Seemed like it was fine but could use better tubes and of course, better bias range and adjustment.

I thought the range was the bigger trouble, not the actual adjustment. Wow, the telefunkin's sounded great tho. A pair in the power section, and one in the lead spot at V1. Mullards at V2 and V3, all new production but the Telefunkins are twice as costly. It's the first time I did not have to turn down my tone knob. The tonal spectrum was rich and notched down to a lovely level with ZERO piercing top end.

For the first time ever, I set the tone on the bridge pickup from 3/4 to full open, and it did not get too harsh!!! The tones was just beautiful, and it felt sexy, it was so good. hehe
Click to expand...

Did you measure the current?
Do you have a bias probe or what?
 
Amp Mad Scientist said:
You need to measure it before you play it.
Click to expand...
I will stop playing it, and wait your instructions, no problem. Like how to check it, with the tubes in. I suppose, turn it upside down, and check the 5 pin for it's voltage, with the standby probably in standby mode, or no sound mode.
 
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