Fuse kept blowing on my triple recto when I on my power

[shinodax]

hi guys,

Whats the reason causing fuse blowing when I on the power switch ( NOT THE STANDBY SWITCH)? My local voltage is 220v to 240v so I will be using a 1000watt step down transformer. I tried 3 4A slow blow fuse and they just blow when i on my power. It's really frustrating. Btw, it's a 2005 triple recto, tubes not changed before.

Thanks!

 

[mikey383]

It could be a few things.

1) Bad power transformer. This is very unlikely though.
2) Rectifier tubes. One of these could be shorted. Most likely the case.
3) Internal short somewhere.

I personally would try removing the rectifier tubes, switch to diodes, and try it again. The way the 3 channel Rectos are wired, the rectifier tubes are always on, even when switched to diodes. So the only way to take them out of the circuit is to take them completely out of the amp.

If that still doesn't work, come back and we'll try something else.

 

[shinodax]

I actually send to a repair shop to repair. But i wan to know answer earlier =X. I think i damaged the recto by using wrong transformer (150w, 300w) or fuses(quick blow 3.15A, 5A , 6A). Those were recommended by the electrical shop cos they don have some parts. /facepalm ... So now i use a 1000w (i was told by mesa that it use 936w(117v x 4A x2) ) transformer and 4A slow blow fuse. but the fuse just blow. So i send for a repair. =(

 

[mikey383]

Well in that case...

Using the wrong size fuse (as long as it's higher rated) won't hurt anything UNLESS there is something wrong with the amp to begin with. So that wouldn't be the problem.

However, using an underrated transformer could cause problems. The amp would be trying to pull more power than the transformer is capable of, so that would drop the voltage the transformer is supplying, which in turn would cause the amp to draw even more current, which would turn into less voltage and heat, and so forth. It would eventually cause something to blow, either it be the supply transformer, or the amp's power transformer.

 

[shinodax]

/facepalm

Thats the info i needed ! Damn, thats gonna cost a bomb to replace.

 

[mikey383]

I just looked through the schematics, and there is a varistor that is connected after the power switch also. A varistor is like a surge protector, and sometimes they can go bad when underpowered. Some amps have them before the power switch, such as the Mark IIIs, but the 3 channel Rectos have them after the power switch.

You may get lucky and the varistor is the only thing bad, or it could just be a rec tube. Keep your fingers crossed, and come back and post when you get the amp back.

 

[shinodax]

Wow thanks a lot. I hope nothing severe happens to it.

I actually play the recto for 10mins with 3.15A fuse and a 150watt transformer. However it gt cut off due to the heat at the transformer. So they asked me to try the 300watt transformers. Now the problems begins. one of the 300w transformer died with fuse blow and the other just died and cant start anymore. After that, the fuse blowing thing started to happen. :x

 

[shinodax]

Is there a possibility that my recto cant be repair in this case? Im really worried.

 

[mikey383]

I wouldn't be worried that it's something that couldn't be repaired. The only thing that wouldn't be able to be repaired is if the circuit board was melted or cracked in half, and I highly doubt that would be the case. It would take a lot for the circuit board to be fried.

My guess goes to a rectifier tube (they are sensitive to voltage fluctuation also), followed by the varistor, then the amp's power transformer, maybe some filter caps.

Worst case, you're looking at replacing a power transformer, which would be a couple hundred in US dollars, possibly more depending on where you're located (I know it's not the US, since you're using a step down transformer )

 

[shinodax]

Hmm... So there a slight power for 1 second when i on it then it blow the fuse. so there's something wrong with the Transformer or tubes etc etc? Not the circuit board?

I hope it's not serious problem. One of my friend actually fried his amp and im afraid i will be the victim as well. I'm staying at Singapore and if it's really the power transformer fault. I would actually buy it from here. http://www.mercurymagnetics.com/pages/mainframe.htm.

Can i add you on msn so i got someone pro to guide me along with my recto? I'm seriously new to it.

 

[mikey383]

There is probably nothing wrong with the circuit board. I'm just saying that would be the only thing that would cause the amp to not be economically repairable.

Most likely, you're looking at replacing one (or more) of the 2 things I mentioned before...the rectifier tubes, the varistor, or at worst, the power transformer.

Mercury Magnetics make some fine transformers, and that would be the way to go if the power tranny is indeed bad, but only if it's cheaper than a Mesa replacement. Mesa power transformers are tough, and there wouldn't really be any benefit to a MM transformer unless it's cheaper to replace.

I'll PM you my contact details.

 

[shinodax]

Thats good to hear. haha. If it's really the power tranny, i will check the price of the mesa power tranny. Received ur pm and added you

 

[mikey383]

For some reason I can't get MSN to install on this computer....but if you have any questions, just email that same address. I'm on here several times a day and I'll get back to you.

 

[shinodax]

Alright then. Thanks for the information u shared with me. I'm looking forward to hearing news from the repair man. Wish me good luck! haha.

 

[Old BF Shred]

....on the bright side it may just be a shorted power supply filter capacitor. Many Mesa amps have these located before the standby switch......That would not be very expensive at all.

Of course if you knowingly had the wrong transformer in there (for whatever reason).....that would indeed cost much more.

I wish you.....
Good luck!

 

[shinodax]

thanks for cheering me up. Hope the repair don cost a lot. i will call them tmr and ask about
it. btw, retubing the whole recto usually cost hw much?

 

[shinodax]

I called the repair shop and they said one of the power tube shattered. LOL!

 

[mikey383]

That would also do it.

Good thing it's not going to be an expensive repair.

Just make sure you power that thing with an appropriately rated step down transformer from now on

 

[shinodax]

yeah so glad that it's the power tube. Im looking to replace all 6 of the 6L6 instead of 1 pair. Any tube recommendations? I was wondering whats the difference between the 6l6 and el34 in terms of sound etc etc..

 

[mikey383]

EL34s are brighter, have a more aggressive top end, more midrange, and less low end. They're sort of a way of putting a little Marshall into your Recto, although they won't turn it into a Marshall. If you go that route, I'd recommend the JJ E34Ls, since they have more of a low end than a standard EL34, or the Winged Cs. I've heard very good things about them, but never had the chance to try them.

6L6s have more lows, more low mids, and the highs aren't as aggressive. I'm not very informed on 6L6s, but I think the preferred brands are EH and Tung Sol, but don't take my word on that. I'm more of an EL34 type myself.

The JJ KT77s are like a hybrid...they carry the lows/low mids like a 6L6, but have the upper midrange and highs like an EL34. That's what I've been running in my Dual Rec lately and couldn't be happier with the tone.