heretic-clown
Registered User
Join date: Jul 2008
1,147 IQ
#1
Have a friend that blew his marshall amp. He isn't the most knowledgeable person in electronics, but here is what he did. He purchased a Randall head, dunno what model it is, i just know it's a hybrid tube/ss amp. Well, he didn't have a cab to run it off of, so he decided to run it through the speakers off the marshall. Not a hard job if you know what your doing. BTW his amp is a Marshall MG 250fx, and if you know about this amp you already know there are 2 outputs in the back of the MG that connect to the speakers, both being 8 ohms and 50watts each. Here's where he went wrong, instead of pluging the randall into the speakers, he plugged the Randall outputs into the Marshall speaker outputs, turned on BOTH amps. Smoke, the Marshall amp started to smoke a bit, he immediately turned it off. Later he tried to play the Marshall, but no noise came out the speaker, instead smoke cameout from the back again. Now, I ask, what could he have possibly burned out. Everything turns on he says, only thing is that the light kinda dims out a little. Could this be an easy fix?
Crank your rig on 12, let it feedback wide-open for a good two minutes, freak your neighbors out and ENJOY THE POWER OF THE GUITAR! 'Oh, what a feeling,' and it ain't no damned Toyota!" ----Dimebag Darrell
TJHague
Registered User
Join date: Feb 2009
480 IQ
#2
Sounds like he is hosed to me. If he's lucky, only the transformer blew. That is not a cheap fix. He might try taking it to a tech, but I highly suspect the cost of parts and labor would greatly exceed the cost of buying another one.
heretic-clown
Registered User
Join date: Jul 2008
1,147 IQ
#3
Lol i kinda figured as much but wanted to see if i can save him a few bucks, it is whst it is. Ill just tell him to take it in tomorrow and see what the tech says. Thanks
Crank your rig on 12, let it feedback wide-open for a good two minutes, freak your neighbors out and ENJOY THE POWER OF THE GUITAR! 'Oh, what a feeling,' and it ain't no damned Toyota!" ----Dimebag Darrell
Robbgnarly
Tab Contributor
Join date: Feb 2011
1,177 IQ
#4
Quote by TJHague
Sounds like he is hosed to me. If he's lucky, only the transformer blew. That is not a cheap fix. He might try taking it to a tech, but I highly suspect the cost of parts and labor would greatly exceed the cost of buying another one.

+1 he is screwed, the MG will cost more to fix than it is worth. Is the Randall amp working now or is it not?
2002 PRS CE22
2013 G&L ASAT Deluxe
2009 Epiphone G-400 (SH-4)
Marshall JCM2000 DSL100
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Krank Rev 4x12 (eminence V12)
GFS Greenie/Digitech Bad Monkey
Morley Bad Horsie 2
MXR Smart Gate
heretic-clown
Registered User
Join date: Jul 2008
1,147 IQ
#6
Quote by Invader Jim
TS, are you any good with electronics?

I'm familiar with electronics, I'm an electrician so i've delt with similar things, but I mainly work on commercial and industrial applications, not alot on tiny circuit boards and the such, I can possibly fix it if i knew exactly what i need and what went wrong.

@Robbgnarly- yes the Randall is in working order and still works...somehow. The only thing that blew was his Marshall, right now all he has is a Spider III 15w amp that pretty much sucks. Sucks that he blew his only decent amp to try out a better amp and is now left with a shitty amp.
Crank your rig on 12, let it feedback wide-open for a good two minutes, freak your neighbors out and ENJOY THE POWER OF THE GUITAR! 'Oh, what a feeling,' and it ain't no damned Toyota!" ----Dimebag Darrell
Invader Jim
?)
Join date: Aug 2005
971 IQ
#7
Well, I managed to find the schematics for that amp here, and this thing uses a power amp IC, which is good news for servicing, I guess.

I'm not entirely sure but forcing the output of the other amp into the power amp IC might have killed it. If possible, take the amp apart and look for obvious damages like toasted resistors and burned spots on the PCB.

If you dont spot any obvious physical damage, the IC itself may be the problem. Digikey has them for 7 bucks a pop so even if that doesn't fix it, you aren't out too much money. Just choose the lead style you need.

http://www.digikey.com/product-search/en?x=0&y=0&lang=en&site=us&KeyWords=tda7293

That's about all I can offer. Good luck...
heretic-clown
Registered User
Join date: Jul 2008
1,147 IQ
#8
Quote by Invader Jim
Well, I managed to find the schematics for that amp here, and this thing uses a power amp IC, which is good news for servicing, I guess.

I'm not entirely sure but forcing the output of the other amp into the power amp IC might have killed it. If possible, take the amp apart and look for obvious damages like toasted resistors and burned spots on the PCB.

If you dont spot any obvious physical damage, the IC itself may be the problem. Digikey has them for 7 bucks a pop so even if that doesn't fix it, you aren't out too much money. Just choose the lead style you need.

http://www.digikey.com/product-search/en?x=0&y=0&lang=en&site=us&KeyWords=tda7293

That's about all I can offer. Good luck...


Thanks a bunch, i'll offer it as an option next time i see him.
Crank your rig on 12, let it feedback wide-open for a good two minutes, freak your neighbors out and ENJOY THE POWER OF THE GUITAR! 'Oh, what a feeling,' and it ain't no damned Toyota!" ----Dimebag Darrell