Frustrated trying to find help.......please help?

Perry Miller

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I have a Marshall JCM 800 4104 I bought in the early 80's. I love this amp but about 6 years ago the tubes went bad. I had a local guy replace them....it lasted about a year and started hissing. I sent it to another local guy and that was a disaster. He lost or broke the presence knob and it played for about two months that time. Last fall I took it to another guy I found on FB about 2 hrs away and he gave it a whirl........it worked for about 3 months and I went to play it yesterday and when I hit the power it immediately made a loud pop and blew the main fuse.

So my question is does anyone know anyone near Greenville SC that really can fix an old tube amp? SO frustrated at this point. I thought maybe I could ship just the amp portion and maybe someone could fix it using their cabinet maybe? I hate to ship the whole amp but maybe I should?

Anyway I'm 6 years and hundreds of dollars out and still can't play it......any help please!
 

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fitz288

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Have you tried the Marshall authorized service locator?


Change the checkbox from retailer to service center, enter zip, hit go.

1644591311077.png
 

Perry Miller

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Thanks, I did try that couldn't find it on the website. All I could find were authorized dealers. I start by giving them a call.
 

Perry Miller

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Ok I called and that's one that lost the parts and didn't get it right. I hate to say that here but that's what happened.
 
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Spanngitter

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JUst asking: What type of fuse to you have in it? Correct rating?
For a 4104 (50W) at 120Vac it is normally 2AT on Mains and 500mA F on HT.
Maybe the only trip you have to do is to the next Home Depot or Electronics Store and get the correct fuse...
 

Perry Miller

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Thanks but the back said 3 AMP & .5A and it blew instantly so I'm pretty sure it's more than a fuse issue unfortunately. It didn't even start to warm up.......just hissed and blew it in less than a second. I'm starting to think these are throw away amps at this point...........lol

Or I have to get some electronics courses...........
 

Ivan H

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Replace the fuses with correct rated "slow blow" types. Might I suggest you make yourself a "light bulb current limiter". You really don't need to have much electronic knowledge to do this, just follow this diagram 16447043974517546356110699675633.jpg
Plug this into the wall socket & your amp into this. It will let you know if your amp is drawing excessive current without the risk of damage to the amp. Hope this helps. Cheers
 

Perry Miller

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Thanks Ivan H.....I'll try that. It did have a fast blow in it but I don't know for how long or which of the techs over the last 6 years did it.
Thems fighting words!

4104's are NOT disposable!

In fact, I would be willing to take it off your hands, sight unseen!
Well.....I can't play it because it doesn't work and now one can or will fix it so that's about the truth...lol. That kinda' is the definition......just seems like a repair wouldn't be so hard to come by.
 

George Dickens

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The licensed Marshall tech you used, the one who lost the knob?
Sounds like he is one.
You could try a new fuse-slo-blos come in packs of 5...for a reason.
Only try it once and then for me I would take it to the tech if it didnt work.
 
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Chris-in-LA

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Did you pull the tubes yet? If it’s still blowing fuses with no tubes you will need a tech.
 

Matthews Guitars

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I'm in Florida and I'd be happy to help you out but you'd have to ship the amp to me. You could yank out all the tubes, take the chassis out, and ship me just the chassis. (Or include the tubes, but box them separately and use lots of bubble wrap, particularly around the power tubes.) Otherwise, I'd use my own tube stash (I've got tons) to troubleshoot it and make it right. Be aware, you may be looking at a bad transformer which is close to a worst case scenario, but since I have spare transformers in my parts inventory I can confirm that it is or is not bad.

Troubleshooting problems that defeat other technicians is my strength. It's because I love a challenge and I've spent many years working on far more complex equipment than any guitar amp ever was.
 

Perry Miller

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Thanks everyone I hope I don't come off as rash......just really frustrated. I'll pull the tubes and put in a slow bow fuse and see what happens. Thank you Matthews Guitar I may be in touch and that would be a HUGE help. Remember when the local Walgreens has a tube tester? Lol
 

myersbw

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I have a Marshall JCM 800 4104 I bought in the early 80's. I love this amp but about 6 years ago the tubes went bad. I had a local guy replace them....it lasted about a year and started hissing. I sent it to another local guy and that was a disaster. He lost or broke the presence knob and it played for about two months that time. Last fall I took it to another guy I found on FB about 2 hrs away and he gave it a whirl........it worked for about 3 months and I went to play it yesterday and when I hit the power it immediately made a loud pop and blew the main fuse.

So my question is does anyone know anyone near Greenville SC that really can fix an old tube amp? SO frustrated at this point. I thought maybe I could ship just the amp portion and maybe someone could fix it using their cabinet maybe? I hate to ship the whole amp but maybe I should?

Anyway I'm 6 years and hundreds of dollars out and still can't play it......any help please!

Perry, there's a lot in your original post that doesn't necessarily reflect on any specific tech's work. First...you state that a local guy replaced the tubes and it lasted a year. What you don't say is...how often do you play? Every day for a few hours? Couple times a week for maybe an hour? Etc. Do you take it to other's homes for jams or venues to perform?

Reason I'm tossing a few questions out is... constant playing for a year can reveal either a poorly biased amp -or- poor care such as...moving the amp from one location to another before the tubes cool down. Or, lot of play tine with a really hot bias and it kept the amp on the edge of red plating.

Also, tubes today aren't likely even close to the durability of old school tubes. I repaired an amp a week back for a client. When he picked it up, he popped it in the back of his F150 pickup...no cushioning of any kind...and just took off with it like that...free to rove all over the truck bed. I just stared and shook my head as he drove off.

And, the other repair lasted 3 months? If an amp survives 3 hours on my bench after use and abuse and all the specs are in line...it's working as expected. I'm not saying the amp doesn't have some issues, but if you played for a year after the first repair? Take it back there. The one thing to remember with a tube amp is...those tubes get a little fragile when they're hot. They need considerate care vs. solidstate amps that you can turn off...nearly toss them in the back of a weak spring pickup bed and they're good to go no matter how much abuse they're subjected to. I had another guy that brought back a JCM900 combo with, repeatedly, broken pots. I asked him,"How do you transport your amps? " And, found it was in the back of his van. But, I found he used no cases or any kind of covers. They were banging around together and that's how the pots busted. He bought Tuki covers and the "problem" was solved.

What you can't expect is for any given amp repair to guarantee your amp to last another 15-20 years with no issue. And, older amps do end up with some hidden issues over time....wire that gets brittle, sockets that arc due to lack of re-tensioning and virtually created short circuit paths at the socket base.

You didn't say where you took the amp, but I'm guessing that amp did (or still does need?) a good refreshening to get it to it's optimum playable reliability...? Have caps been replaced or at least tested? What tubes are you putting in it.,, But...again...the longevity you get after a repair isn't always a reflection on what the tech did. As for here in this group...try giving us a lot more detail...how often you practice? Do you gig? Are you transporting it warm, etc.

The more detail you give in those areas, including specifically what was done to the amp...the easier it is to help troubleshoot a little. Also, you did get some great advice above on pinpointing whether a the issue is a tube or lies elsewhere.

Cheers!
Brad
 
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Perry Miller

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Thanks myersbw, I rarely play the amp. Since the amp started failing about 6 years ago I pretty much stopped playing. I have bought several amps Fenders, Bugera, and a Blackstar and just can't get the sound so I'm not playing. I probably play once a month for an hour since then. I want to get back to playing but I can't get the amp going...........so I lose motivation and push off getting it repaired.

I never gig anymore I just play at the house so the amp is in the house and never moved. When I picked it up in my van and I tied it down in my van and placed it on high density foam I get form work because I do know moving the amp is rough on the tubes. It hasn't moved since that day I got it home.

I thought about taking it back to the guy that fixed it and I might depending on what I find out by pulling the tubes and replacing the fuse. I guess a little history is needed. I bought the amp in 83 "I think" but since then I never replaced the tubes until after 2005. Don't know what tubes they were factory or what but I used the amp quite a bit more back then and traveled with it so I would hope 6 months to year wouldn't be too hard on it?

I'm have heard the new tubes are not well made but I sure hope they aren't so different they have to be changed annually under the conditions I use the amp. The last guy seemed good and knowledgeable and that's why I'm not naming names I would hate to be unfair to anyone....he replaced the caps even though they were working because he said they were very old. He replaced the tubes as well but I'm not sure which ones exactly. He seemed great so maybe I'll call him when I find out more and see what he says.

I guess what is strange is why it lasted so long under the same circumstances (or worse as I traveled) and it seems like it won't last more than 15 -30 hours before it goes down now. That's been going on for the last 6 years and before that (I guess I was super lucky) but it lasted literally for decades.
 
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Perry Miller

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Ok after the amp blew the fuse I checked the fuses and the 500 ma fuse was good. The 3A was black and obviously bad. Next as suggested I pulled the 2 power tubes and replaced the fuses with known good ones. The amp powered up when I turned on the main switch and hummed softly as normal. Since it didn't blow either fuse and stayed on next I turned the standby switch on and again it stayed on and didn't blow either fuse.

I took a picture of the 2 power tubes which are Apex tubes. So I take that means the tubes (or at least one) is bad? IMG_2291.jpg
 
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