Marshall JCM 2000 is making strange noises

[Securb]

As for your practice space its a mess you'll likely have to live with it.

One of the guys in our circle of friends is an electrician if we need to bring him in it would not be too hard on the pocket with 20 guys sharing the space. The last time we had a major expense everyone kicked in $100, not too hard on the pocket seeing we pay $40 per guy per month for the space.

I got the plug-in voltage meter today and played with it in the house a bit. The house reads ~120v-121v. I had the meter in the kitchen, the kitchen is on a 20 amp circuit. When I turned on the dishwasher it dropped to 116v and then came back up to 120v. It dropped a volt when I turned on the air fryer and returned to 120v. I am dying to see what happens in the practice room. Our singer just came down with Covid so there is no practice until next week. I will have to wait until then to check it out in the room.

 

[Demanic]

120 solid at the house? Nice. No thanks to Seabrook I'm sure. Like you said, the practice space could be a different story. I'll be interested as to what it shows.

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[Montana O.G.]

I owned a Marshall

 

[Montana O.G.]

I owned a Marshall half stack in the 70's-never had a problem like that but I was changing tubes every 2 or 3 years; think this is where I'd start

 

[Securb]

I owned a Marshall half stack in the 70's-never had a problem like that but I was changing tubes every 2 or 3 years; think this is where I'd start

Yep, I grabbed the head today so I can look at the tubes and the bias. I also checked the power in the practice room with all of the gear and heating system off the power was reading at 116v. It will be interesting to see what it reads when everything is powered up.

 

[JMP/HBE]

Yep, I grabbed the head today so I can look at the tubes and the bias. I also checked the power in the practice room with all of the gear and heating system off the power was reading at 116v. It will be interesting to see what it reads when everything is powered up.

Typical USA AC line voltage is anywhere from 109 to 129 vac with 115 to 120 being average.

 

[Securb]

Got the Marshall home, plugged it into the 2x12, and it sounds glorious. No issues whatsoever. The tubes visually look good and the tap test yeilds nothing. I just talked to the oldtimer that owns the local TV repair shop. He told me to bring over my tubes. He will show me how to use his tube tester, and I am free to use it any time at no charge. I am going to bring him some type of gift card. That kind of kindness needs to be appreciated.

 

[ErikH]

That right there indicates there is dirty power in the rehearsal building. And it's enough to affect not just your amp, but others as well.

I get that tubes go bad and filter caps need to be changed but when it's fine in one place but not fine plugged in elsewhere, and the only change is the electricity source, it's pretty hard to not ignore that.

Is this 2x12 the same as what you use at the rehearsal space? Or are you using a 4x12 with different speakers? Simply curious. I didn't see where that was mentioned to eliminate the cabinet as a potential issue.

 

[Ewizard]

Knowing now that you have a limited number of circuits powering MULTIPLE devices definitely makes the power a suspect. As you can imagine, if the band is drawing perhaps a full circuit worth of energy with the PA's and lights kicking, and then a Refer, A/C and other peripherals going, you are loading down the mains quite a bit. I would venture a bet if you turn off all the unneeded lights, the A/C, the Refer, and everything else but the band and PA, you will have no issue at all.

 

[Securb]

Is this 2x12 the same as what you use at the rehearsal space? Or are you using a 4x12 with different speakers? Simply curious. I didn't see where that was mentioned to eliminate the cabinet as a potential issue.

It is a different cab I use a 4x12 at the space the 2x12 is in my home office. I do not get the blown sound with my JC 120 or Carvin X100B, I used the Carvin head with the Marshall 4x12 cab at the last practice with no problems. I also did a check on the speakers with a multimeter and tightened up anything that could be potentially rattling in the cab.

I am checking the tubes this weekend and will have the chance to monitor the power with the full band, PAs, and appliances going hopefully next week.

 

[NegativeEase]

B, if you get into looking into power conditioning -let me know -I spec it everyday for studios and live rigs. Got my favorites, my avoids and economical options.

 

[Securb]

I could not be happier. I went to the old-school TV repair shop one town over. The oldtimer that owns the place showed me how to use the tube checker. I pulled all of my glass with the exception of the Fender, which has all brand new glass. Two of the 12XT7s from the JCM 2000 were faulty. I have extras, but I am open to suggestions if anyone has some preamp tubes they love, they think I should try.

All of my other glass, including some 50-year-old tubes, tested perfectly. I not only checked the tube quality, but the guy also showed me how to check them all for shorts. He told me I am welcome to use the machine for free whenever I want.

 

[JMP/HBE]

Did you change the spec settings from 12AX to 12AT when you tested those ?

 

[Securb]

Did you change the spec settings from 12AX to 12AT when you tested those?

Yep, I tested the EL34s, the 12XTs, and then the 12ATs.I adjusted the settings for each batch. It is a relatively simple machine to use it took less than a minute for the guy to show me how to use it.

 

[JMP/HBE]

I picked one up a few years ago on CL fairly cheap.
When i was a kid in the 60's & 70's every corner 5 & dime and drug store had a tube tester with a cabinet below the machine full of tubes.

Be sure to let the heaters in the tubes warm up a few before pushing the button to test.

 

[Securb]

That is really cool. We were talking about building a dedicated tech station in our rehearsal space. Right now we have to do set-ups, string changes, and minor guitar surgery on the bar top. One of the things we are considering adding is a tube tester. Do you mind me asking what you paid for your tester? I am seeing prices all over the place.

 

[JMP/HBE]

That is really cool. We were talking about building a dedicated tech station in our rehearsal space. Right now we have to do set-ups, string changes, and minor guitar surgery on the bar top. One of the things we are considering adding is a tube tester. Do you mind me asking what you paid for your tester? I am seeing prices all over the place.

$70

 

[Securb]

That is a freaking steal beautiful score.

 

[JMP/HBE]

Alot going on under the hood but pretty pristine for 50+ yrs old.
Like you i got it from an older electronics guy.
I few months later same guy had another one for sale, same kind. I would have snagged it if i could have.

 

[Demanic]

Wow. I envy you both. For having one and for knowing how to use one properly. Best I can do is throw one in my Picovalve and play it. And if it starts acting weird, I know that it's on it's way out. Oddly enough, tubes sing a swan song. Right before they die, they tend to sound the best that they ever have. Then within a week or so, bloop.

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