American triple rectifier damaged by European voltage

[ducktape182]

Hi sorry for being a nOOb and creating a topic as my first post but I have a big problem

I own a 2 channel triple rectifier which i bought second hand from the US and have used in Ireland (220v same frequency as UK) with a 300w step down transformer perfectly for about 10 years.

Now I am selling the amp and I brought it to a potential buyer for a trial and before I had a chance to plug in the transformer he plugged in a europeand lead and without the amp being turned on a spark flew and the house electricity tripped. Then I plugged the amp into the transformer and it blew the built in fuse in the transformer, i tried new fuses but same result. Then I brought the mesa fuse from the amp into maplan (UK electronic store) they said there is nothing wrong with the fuse most likely the amp.

Does anyone know the damage this could have caused the amp? and is it repairable? or is it completely F'ed?

Long story short I think the guy has burned the inside of my amp. There is no visible damage to the outside and the fuse was never blown.

 

[fluff191]

Wow. Sounds like that guy bought himself a Mesa Boogie Triple Rectifier.

 

[domct203]

Wow. Sounds like that guy bought himself a Mesa Boogie Triple Rectifier. S

+1

You break it, you bought it.

Dom

 

[cheameup]

I'm no expert but if its not completely fucked I'd say it wil be a major rebuild. tubes and transformers I'd guess and whatever the transformer burnt in its path

+1 to fluff and dom. he's the new owner of the problem if its my amp

 

[ifailedshapes]

My vote is this: the guy pays for the repairs, but if the repair cost exceeds the value of the amp, he gets to buy the amp he fried.

 

[Dave G.]

Where in Ireland are you based? If you are near Dublin take the amp out to XMusic. They have a good repair centre there as far as i know and are also Mesa dealers so they will give you a good quote on a repair. As mentioned if the repairs are dearer than the amps worth that guy just bought himself the amp!

 

[ducktape182]

Ya im bringing it to xmusic next saturday to get a quote i explained it all to him and he just said hopefully the power transformer aint gone!

 

[94Tremoverb]

The usual failure modes when you do this are either that the amp blows its own fuse - no damage except for the fuse - or that it blows the primary winding of the amp's power transformer. A blown fuse in the amp gives an open circuit, so after that it simply doesn't power up.

It's not hopeful if it blows the fuse in the step-down transformer. That means the amp has a short inside, not an open circuit. The most likely reason for that is a damaged transformer. If you're lucky (although that's debatable at this point) the primary winding shorted before it fried anything else in the amp's circuit, but even that isn't a certainty.

If you need to get it fixed yourself, fit a European voltage transformer. It will cost a lot, Mesa parts in Europe are very expensive.

 

[ducktape182]

When you say get a European transformer do you mean that the internal transformer will be European removing the need for the external step down transformer? I am bringing it to a repair man at the weekend. I took a look at the back of the amp and took out tubes and no sign of burns of smell of singed metal so that must be a good sign but yes It could well be circuitry broken. hopefully its only a small capcitor blown, i work at analog devices so hopefully they have loads a cheap parts lying around

 

[94Tremoverb]

Yes - if the power transformer is blown, get a UK/Euro voltage one fitted not a US one, and you won't have this problem again.

It's unlikely to be any kind of small capacitor that's blown - if there is a short in the amp (pretty much the only thing that would blow the fuse in the stepdown transformer), the only type of cap that could be blown and do that is a main filter cap.

If you're lucky, it may be a rectifier diode (1N4007) or more than one of them, since that would produce a near-short that could blow the transformer fuse but not the one in the amp (which is also a clue that the stepdown transformer isn't really heavy enough for the job, by the way!).

I wouldn't bet on anything at this point though. Mesa transformers are tough and it's rare to blow one - I've never seen one personally, in a couple of decades repairing amps - but slamming it with double the designed voltage is about the best way to do it.

 

[ducktape182]

Thats for all the help. I will update the information after I get it checked on saturday it might be interesting to know.


The step down transformer only blew on an attempt to plug in the amp with the American lead after the EU lead was plugged in so The transformer defiantly didn't cause a problem during the time I used it. It has a safety spec up to 300 watts and I think my amp is 150w correct me if im wrong but I will ask the repair guy when I meet him saturday.

 

[domct203]

Thats for all the help. I will update the information after I get it checked on saturday it might be interesting to know.


The step down transformer only blew on an attempt to plug in the amp with the American lead after the EU lead was plugged in so The transformer defiantly didn't cause a problem during the time I used it. It has a safety spec up to 300 watts and I think my amp is 150w correct me if im wrong but I will ask the repair guy when I meet him saturday.

300W is not big enough. Following Ohm's law, the amp could draw almost 500W before the amp's 4A fuse would blow (120(v) X 4(a) = 480W). The 150W you mention is the output power of the amp, not the wattage draw of the power supply.

Good luck with your troubles, and please do post the result from your tech.

Dom

 

[94Tremoverb]

The step down transformer only blew on an attempt to plug in the amp with the American lead after the EU lead was plugged in so The transformer defiantly didn't cause a problem during the time I used it. It has a safety spec up to 300 watts and I think my amp is 150w correct me if im wrong but I will ask the repair guy when I meet him saturday.

No - 150W is the power *output* of the amp. The stepdown transformer needs to be able to supply the power *draw*, which for a tube amp is typically 3-4 times higher than the output, ie around 500W for that amp - that's why I said that a 500W transformer is the minimum you should use and 1000W is better (for safety margin and to avoid 'sag' under load). But, this is only if you crank it, so you will get away with a lower-rated one as long as you don't - at low volume the amp will be drawing a lot less power, probably only around 200W*, so it will work with a 300W transformer. Still not a good idea really.

The fact that the stepdown transformer now blows its fuse when it didn't before does show that there is a fault with the amp though.

(*The output section is around 50% efficient, so out of that roughly 500W draw, about 300W is the *extra* power used when the amp is running hard. At low volume you're down at the 'background' draw, which is the power for all the tube filaments, the idle current and the low-voltage supply for the channel switching.)

 

[ducktape182]

good news i got the amp fixed for free.

He opened up the amp and saw a component fried before the transformer, Its a failsafe device i think he said he will email me the part number on monday, but basically the 240v blew this failsafe which acted as a short, all he had to do was cut it out and it was an o/c again. now the amp works perfect but if a irish plug goes into it again its the amp that will be fried. but aparently the part only costs about 5€ so better to be safe than sorry and all i have to do is solder it in.

So great news

 

[94Tremoverb]

Excellent. That's the surge suppressor which blew. Surprising, since I'm pretty sure they're rated for 250V even in US amps (it's the standard voltage) and they usually fail open circuit! That's why I didn't suspect it. But there you go... shows how tough the transformers in Mesa amps really are - it survived when the component designed to protect it didn't .

 

[ducktape182]

HE told me that the mesa transformers are like 200$ but they charge $400 in the europe for them. aparently scotland distribute them which is really **** but aparently they dont want people buying an amp cheaply (relative to europe) in the us making it eu freindly

 

[ducktape182]

One final thing guys, how much would you value this amp at?

Here is a link to it. Its the amp I had to get fixed.

http://www.adverts.ie/amps/mesa-boogie-triple-rectifier-original-2-channel/446940

 

[94Tremoverb]

At €1,100 for the head and €2,200 for the whole rig, you have the head underpriced and the cab maybe slightly overpriced, even with the case. Two-channel Triples are rare and quite desirable.

Not sure about Irish prices but in the UK the head should sell for around £1,200 (GBP, not €), even with the wrong footswitch and what we know about its history . The cab would be more like £500, plus the case at about £100. It's really hard to sell a box with four speakers in it for a lot of money, no matter how expensive Mesa cabs are new in the EU.

You really do need to either upgrade the stepdown transformer or sell it without and insist the buyer gets his own though - if he cranks the amp fully, he will blow the transformer fuse (if it's the correct value) and then you'll be having to explain why to an annoyed customer.

Put a matchstick and some white glue (if you have any) in the stripped screw hole, it's a lot more professional than Blu-Tac . Put a drop of glue in the hole, pack in a couple of bits of matchstick (enough to just fill the hole, but not really tight) and put the screw back in while the glue is wet.

 

[ducktape182]

Cool thanks, ya I fixed the tube protector with a screw since I took the photos.

Ok I was checking ebay and the price is similar to 1,100EUR. Ya the cab and head package was a little over priced on purpose I was happy to hold on to the cab unless I got a great deal.

The guy who broke it was offered the same amp for €1,000 but said seen as he screwed up mine he would buy mine for 1,050 to split the difference from what i wanted €1050.

I will just have to think about it.

Thanks again for all the help. The repair man emailed me and said its a MOV that blew and recommends getting a new one.