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PostPosted: Thu Sep 21, 2017 3:29 pm 
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Bottle Rocket

Joined: Thu Sep 21, 2017 3:20 pm
Posts: 3
Hi All,

Im new here and from the UK, so apologies if this question has been asked before.

Did a gig the other week and ended up borrowing an amp because one of the stage hands decided to "help" me set up, picked up my US Tremoverb head and plugged it in to 240v. Legend......

Im currently sourcing someone to repair it, but just wondered in the mean time if anyone knows what kind of damage may have been done

Cheers
Dan


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PostPosted: Thu Sep 21, 2017 3:51 pm 
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Mark II

Joined: Thu Jul 07, 2016 1:18 pm
Posts: 78
If you're VERY lucky it's just blown the main fuse - have you checked it?
But more likely i'm afraid it's blown the transformer. Theres a company in Germany called TAD that can supply you with a new one, then its a case of finding a competent tech to fit it.

I use a 110v Boogie here in the UK with a stepdown transformer, and it's my worst nightmare having someone 'helpfully' plug it in.
Good luck and let us know how you get on...


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PostPosted: Thu Sep 21, 2017 4:02 pm 
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Bottle Rocket

Joined: Thu Sep 21, 2017 3:20 pm
Posts: 3
HI Nick,
Yes, when i was the other side of the room and turned round to see a bloke plugging my amp in whilst i still had my transformer in my hand, my heart sank.
No i havent, i assume thats an easy change? Im not too hot on amp tech to be honest.
To be fair the amp absolutely stunk after, so im assuming its done a bit more damage than the fuse, but ill keep my fingers crossed

Thanks for recommending TAD.

I'll keep you posted

Cheers
Dan


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PostPosted: Fri Sep 22, 2017 6:10 am 
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Mark II

Joined: Thu Jul 07, 2016 1:18 pm
Posts: 78
The fuse is easy to check

Image

Just up from the mains input socket you will see it, its behind a black plastic circular cover.
Chances are this has gone, but its also more than likely taken out your transformer too unfortunately.

Best thing to do is find a good amp tech and let them see whats what. Whereabout's in the UK are you?

Nick


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PostPosted: Fri Sep 22, 2017 11:38 am 
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Bottle Rocket

Joined: Thu Sep 21, 2017 3:20 pm
Posts: 3
Thanks Nick, ill take a gander.
fortunately the amp never got turned on, so I'm hoping the damage has been limited.

I'm in the west mids.
I used to work for a company that manufactured pro audio equipment (Midas/Klark Teknik), ive been in touch with one of the old R&D guys who also builds his own amps, and he reckons that if it didn't get turned on, worst that should have happened is the MOV popped.
So with a bit of a clean up, it will hopefully spring back in to life.

failing that he's going to take a look for me

Cheers for the help Nick

Dan


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PostPosted: Fri Sep 22, 2017 11:57 am 
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Mark II

Joined: Thu Jul 07, 2016 1:18 pm
Posts: 78
Ah if it wasn't actually turned on then there is hope yet.
Good luck with it mate and let us know how you get on.


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PostPosted: Mon Sep 25, 2017 1:05 pm 
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Single Recto
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Joined: Sat Jan 12, 2008 12:32 pm
Posts: 1283
If the amp was not turned on then he just blew the MOV (varistor). This protects the circuit from input over a certain voltage. They smell bad when they go! Easy fix!


Last edited by Don on Mon Sep 25, 2017 1:07 pm, edited 1 time in total.

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PostPosted: Mon Sep 25, 2017 1:06 pm 
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Single Recto
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Oops!


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PostPosted: Tue Sep 26, 2017 6:26 am 
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Dual Recto

Joined: Fri Feb 22, 2013 7:31 am
Posts: 2726
Location: North Carolina
:P oops is right.... Unless the tech decided to replace the blown fuse with a metal slug or wrap it in aluminum foil (I think that would be worthy of a smack in the head with the body of your guitar, well perhaps things should not go that far, it is the thought that counts).

the fuse should blow first before the MOV blows out when it is forced into clamping. All depends on how many joules are passing though the MOV if that decides to go. MOVs can turn into a Roman candle and do lots of damage once they are forced into conduction (areas close to the MOV will be cut though as if done by a plasma torch. I have seen many product that had an MOV fail and it is not pretty). What could be worse, turning the amp on in sponge or variac mode as this will pass some of the current thought the power transformer before it is coupled to the MOV. I doubt there would be any transformer damage unless the fuse was not correct type. You do however have a risk of exploding the capacitors on the secondary side as well as the other accessory taps will be double the voltage or higher. It could be a mess for repair as it may depend on how long it took the fuse to blow, based on the MOV it would be almost instant.

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Current amps: TC-100, TC-50, JP-2C, MK V, Roadster, RA100


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PostPosted: Tue Sep 26, 2017 8:05 am 
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Single Recto
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Joined: Sat Jan 12, 2008 12:32 pm
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It depends on the design and how they implemented the MOV. We had a run of products here (I design solid state lighting) blow MOVs due to a bad installation. The were emitted thick, acrid smoke and made a mess inside the product but were not difficult to repair because the MOV was located away from other components.


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PostPosted: Wed Sep 27, 2017 5:58 am 
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Dual Recto

Joined: Fri Feb 22, 2013 7:31 am
Posts: 2726
Location: North Carolina
I had a review with UL on a 120VAC Brushless DC motor driver control used with pre-mix gas fired boiler systems. It had a non-replaceable fuse located after filters and MOV just in front of the bridge on one leg and the other used an In-rush current limiter thermistor on the other. They recommended the fuse be moved to the circuit before the MOV. Good advice... The MOV basically acts as a crowbar for overvoltage conditions to blow the fuse and render the product safe in the event the product it was installed on 208-240VAC supply. Failing with grace is good. Failing with fire, arcing, and sparks flying everywhere along with toxic fumes is bad. Sometimes getting a product to fail under extreme conditions (say 700VAC or more with moderate current can be fun, and if it fails with nothing very exciting that is job well done). I had to run a test that high as I was trying to find the limit of failure on a product that uses a switching power supply (did not have any MOV or TVS devices). The sacrificial test for failure can be the fun part as long as you know you are expecting failure. I already had a motor rotor explode in my face and I am happy I was using a blast shield (was a new motor design and I was dialing in the parameters for the motor controller and then bam, crap went flying everywhere and those ceramic magnet fragments are very sharp too. that was not a test for failure either.

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Current amps: TC-100, TC-50, JP-2C, MK V, Roadster, RA100


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