output transfo kaputt

[Tirol29]

Hello,

while playing at max volume on my diy amp (cf:  https://el34world.com/Forum/index.php?topic=25354)
suddenly there was a big noise . i stop everything when i retry no sound at all.
After look out on the bench,  it occurs that the output transformer, a classictone 40-18031, was sparkling, i dismounted it and found burn wires

do you know what could be the cause ?
i am ont the way to buy a hammond 1750B i think that's correct.

[shooter]

do you know what could be the cause

EXCESS current at the other end of those wires most likely the cause
so the PA tubes bias, the tubes themselves, and surrounding parts in the PA

[Tirol29]

tks shooter,
i have another 6v6GT (old mazda Belvu) i will put in place when i will have wired the new transfo, in case it was the cause (which is the most likely)

[sluckey]

while playing at max volume on my diy amp

This is most likely the cause.

[Tirol29]

while playing at max volume on my diy amp

This is most likely the cause.

and maybe another related cause : friday evening and big muff 

[dude]

and maybe another related cause : friday evening and big muff 

What's Big Muff..

[bmccowan]

What's Big Muff?

BYOC has a diy version named Large Beaver.
https://buildyourownclone.myshopify.com/products/large-beaver-rams-kit

[shooter]

since you said "I have another 6V6GT..."  is this a PP or SE amp?  Got a schematic?  might help so you don't repeat.
my builds like the Big Muff and everyone on 10, but I take that in consideration when I by Iron, how I bias the amp, and what size ah-sheet fuse to use

[scstill]

What's interesting is that in reply #10 of your earlier post on this amp (btw this link shows SE with schematics), the 8k red lead looks to be connected to the terminal strip without a corresponding connection, yet that is the wire that seems most fried. Seems that somehow high current flowed through red. When I have unused transformer leads I will just heat shrink  the ends and tuck away in the chassis.

https://el34world.com/Forum/index.php?topic=25354

[PRR]

The power tube shorted. Happened on a VT-40. Smoked the irreplaceable OT and stunk-up the room.

So replace your power tube before you burn your new OT.

[Tirol29]

What's interesting is that in reply #10 of your earlier post on this amp (btw this link shows SE with schematics), the 8k red lead looks to be connected to the terminal strip without a corresponding connection, yet that is the wire that seems most fried. Seems that somehow high current flowed through red. When I have unused transformer leads I will just heat shrink  the ends and tuck away in the chassis.

https://el34world.com/Forum/index.php?topic=25354

at that time of picture it was not yet 100% completed. Since then unused wires have been soldered to free terminal tags before first power on 

[Tirol29]

The power tube shorted. Happened on a VT-40. Smoked the irreplaceable OT and stunk-up the room.

So replace your power tube before you burn your new OT.

thanks PRR,
that's what i said in answer #2. For the actual and suspicious tube i'll contact on OM who has several tube testers. At first sight i don't see any trace of overheating but that  means poor i guess.
Do you agree with Hammond 1750B choice ?

[mresistor]

Uncle Doug used a 15w classic tone OT   the1750B is 10w.  A Hammond 125ESE is 15w with lots of hookup options.


If you are only using a 6V6 then the 1750B would work and it's half the price of a 125ESE.

[66Strat]

Hello,

while playing at max volume on my diy amp (cf:  https://el34world.com/Forum/index.php?topic=25354)
suddenly there was a big noise . i stop everything when i retry no sound at all.
After look out on the bench,  it occurs that the output transformer, a classictone 40-18031, was sparkling, i dismounted it and found burn wires

do you know what could be the cause ?
i am ont the way to buy a hammond 1750B i think that's correct.

My bet would be square wave induced fly-back voltage spikes. You may want to consider implementing fly-back voltage protection diodes.

[PRR]

that's what i said in answer #2.

Sorry.

....i don't see any trace of overheating but that  means poor i guess.

Last year the muffler fell off my car. I think the same thing sometimes happens in vacuum tubes: parts come loose. Except the other electrodes and the glass bottle keep them from falling out on the road.

[Tirol29]

that's what i said in answer #2.

Sorry.

no no you don't have to ! i didn't express any frustation or what so ever.   

[PRR]

_I_ get frustrated when people do not read the thread.

I am sorry to be guilty of this myself. I will give myself 12 lashes with a stale cheesecake. (Long story........)

[mresistor]

oh   stale cheesecake   ummm     what a waste

[Tirol29]

hi,
received and replaced OT with 1750B : all fine 
Boys are back in town
another success for the working class