I am cursed definately.....help me!

Jethro Rocker

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yes i replaced and biased my JVM 410....but JCM 800 is a different beast....you cant bias it that easy....with just multimeter...you need special attachments that I dont have.....and it sucks
Bias comes AFTER finding out power tube has died and if fuse is dead, if so, what made it die? Dead tube?
That is troubleshooting. Don't jump in amd buy fuses right aaay although you should have spares on hand.
Point is, a fuse dies for a reason as stated here. Figure out if it is dead and why, first.
By the way, a dead V1 preamp or PI tube cam kill the output as well.
 

Gene Ballzz

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@bobbyvasco ,

Is your real name actually "Joe Btfsplk" 'cause you always seem to have a dark cloud chasing you? :p

joe btfsplk

joe cartoon



Just Askin'
Gene
 

PelliX

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My JCM 800 just died....it worked now for few months after I bought it from a guy.
The problem is it went quiet all of a sudden. So it is probably not a preamp tube going bad.

Your definition of 'died' varies from thread to thread. Sometimes dead means no pilot light or power at all, other times it means the amp is producing less volume than expected. This could well be a preamp valve - but I'm going to assume that you've tried replacing it after all the extensive troubleshooting and past mishaps with amplifiers, speakers, gear, etc... right? :)

Damn.....
i have to send back the 1960 cab and this amp is dead in the same week......

Ah yes, the cab. It probably has a blown speaker from the oscillation/feedback that got inflicted on it. Ah well, live and learn. Ideally, combine them without much delay in between...

and also my DENON surround receiver died few days ago....LOL

Seriously, are you rough on gear or do you maybe have dirty AC mains? That won't account for the feedback or speakers blowing, but a (solid state?) hifi amp generally goes on for years...

where is the fuse for jcm 800 i think i replaced one in jcm 900 a while ago

Same place. Check the back. The fuses are marked, labeled and the old one has its value stamped into the metal cap(s). Are you *sure* you replaced a fuse in the 900? How did that even die actually? We should add that one to the list in your HoF....

yes i replaced and biased my JVM 410....but JCM 800 is a different beast....you cant bias it that easy....with just multimeter...you need special attachments that I dont have.....and it sucks

You can bias it using a multimeter, but... bias....? @Jethro Rocker (and others) are spot on when they say "find the cause".

Now, whenever you get fed up with all this gear breaking, keep me in mind. The legendary BVM line are becoming increasingly famous.... :coffee:
 

steveb63

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Quit futzin around and find a tech.

Then he will explain the problem, fix it, and only then will you really know what failed.

Of course, that's just my opinion.

After using my Marshalls heavily these past.... oh...... fifty years more or less.

The shot gun approach rarely works out well, financially or otherwise.
 

PelliX

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Seriously, Bobby - I'll buy the broken kit off ya at a fair price. I bet I could restore some of those BVM's.

Quit futzin around and find a tech.

Then he will explain the problem, fix it, and only then will you really know what failed.

Of course, that's just my opinion.

After using my Marshalls heavily these past.... oh...... fifty years more or less.

The shot gun approach rarely works out well, financially or otherwise.

C'mon, stop trolling the poor guy... ;)
 

steveb63

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Seriously, Bobby - I'll buy the broken kit off ya at a fair price. I bet I could restore some of those BVM's.



C'mon, stop trolling the poor guy... ;)
At this point I'm calling it "constructive criticism"

Reminds me of my younger brother after buying his first car, ran great when he bought it.

But had to go monkeying around under the hood until he "found" something wrong. Mechanic's diagnosis was my bro had ADD and just couldn't help his self, played around until he "fixed" something that the mechanic had to replace.

Critical thinking and a problem solving menu tree would go a long way. :thumb:
 

steveb63

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Just want the o.p. to enjoy playing music with his Marshall, as much as I love playing mine.






Might be a little trolling Lol- but Hell, that's my nature Lol.
All in good fun people, I am not trying to hassle the poor guy.
 

bobbyvasco

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Actually, you can bias it with just a multimeter.
is tehre a good totorial how to bias JCM 800 2210 because it will be cheaper to replace all tubes and bias it myself then to give it to tech who will replace only 1 tube and charge me the same
 

PelliX

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is tehre a good totorial how to bias JCM 800 2210 because it will be cheaper to replace all tubes and bias it myself then to give it to tech who will replace only 1 tube and charge me the same

Scenario A) Tech decides the output valves are 'too old'. He would replace them all with matched valves (or he's an incompetent tech not worth his salt).
Scenario B) Tech decides that one or more of the preamp valves have gone bad. No biasing required.

So I don't know whether he's been feeding you a line, but... anyhow:



This is basically, from what I saw quickly, the applicable procedure. Note that he installs 1 Ohm resistors which (long story short) allow you to read the bias easier. I would leave them in after you're done for the next time, though. No need to remove them if they're properly installed. If you don't feel comfortable poking around in the amp, by all means get the bias sockets.... you'll probably need to shop for the 1 Ohm resistors anyway...

HOWEVER(!) perhaps you should start with checking the rest of the amp. Fuses don't tend to blow because your bias is a bit skewed. Valves do suddenly go bad from time to time, but I would urge you to at least perform basic troubleshooting and send us some gutshots... People here have provided solid advice (referred to as 'trolling' at times), and you would be well advised to follow some of it. :yesway:

I feel this JCM may become a BVM soon.
 

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