Power transformer fails

[martin manning]

I don't see any mention on Weber's site that this transformer can be used with 50 Hz power. It only mentions "US voltages Power Transformer," which implies 60 Hz.

[Roe]

I don't see any mention on Weber's site that this transformer can be used with 50 Hz power. It only mentions "US voltages Power Transformer," which implies 60 Hz.

they have been seeling some export transformers but it is exactly these export transformers that often overheat with 50hz AC power

[Stevem]

For 50 hz usage the iron core would need to have at least 17% more mass to get the same energy transfer.

[Oddvar R]

I don't see any mention on Weber's site that this transformer can be used with 50 Hz power. It only mentions "US voltages Power Transformer," which implies 60 Hz.

This is the INT version, made for 240v

[Roe]

I don't see any mention on Weber's site that this transformer can be used with 50 Hz power. It only mentions "US voltages Power Transformer," which implies 60 Hz.

This is the INT version, made for 240v

the problem is not 240v but 50hz AC

[Oddvar R]

Weber answer, the one I got:"The 50/60 Hz should not be a problem at all of it working/not working/working. Normally if a transformer goes bad, one of the windings will either open (most common) or short."

Ad the mA, seems lik 200mA should be enough?: https://thesubjectmatter.com/calcptcurrent.html

[martin manning]

A quick and dirty estimate of the current required: 50W/330V = 0.152A, At 50% efficiency, that's 300 mA.
It won't be running at 50W 100% of the time, so 66% efficiency might be more realistic, for 230 mA.
I would say the Weber unit is right on the edge. A better bet is this 270 mA Hammond Bassman replacement: https://eu.mouser.com/ProductDetail/Ham ... 3P7Q%3D%3D

[bepone]

I have bought three Weber W022798 power transformers to put in a Dumble 50w ods. The amp itself sounds great, and the transformers works great for a awhile, the it starts blowing fuses. I have tried to search for every possible reason, but the 100w bulb limiter lighst up even when all the secondaries ar disconnected. I have tried to contact Weber, but they never answer anything. Strange that it happens 3 times, works for a while, one month, two months, and the goes the fuse. What can cause a PT to blow fuses. I have done almost anything I can think of, following the advice on robrobinette site on PT failure. I am not an pro amp builder, but I have buildt more than 20 amps that all works great. Anyone shedding a little dimmer bulb light on this?

Did you measure temperature on the transformer during operation?
Transformer can blow anytime, depending how good are internals (insulation between the windings) and how thin is the wire inside. Nobody can say here what is inside. If is blow several times, this means transformer are not OK made. If wire is too thin, then wire will just blow and disconnect secondary, but here you have short circuit, means not ok wound.

Specifications are OK for 50w i dont know what all people here are speaking about, all standard specs.

[bepone]

is it possible to measure this dimension?

w022798sch.JPG

[bepone]

parameter what is important is core magnetic flux - and this is ofcourse not stated anywhere and this can cause overheating of transformer if the primary turns are too low (too high flux), and can be estimated by measuring temperature of transformer during operation (my question above) or do roughly reverse engineering via mechanical parameters (stack - my second question)

[Oddvar R]

is it possible to measure this dimension?
w022798sch.JPG

It's 48 mm.

[bepone]

It's 48 mm.

I put values in tables..with this dimension, it is possible to wind normal transformer (which will be in normal temp in use) with specs from datasheet - for 120VAC and 60 Hz primary. But for 230V and 50 Hz not, stack must be at least 55cm or lamination one size bigger (EI115-120).

So i didnt change my conclusion. If the temp is normal, can be clumsy wound.. if its too high temp, then primary turns are too low for dedicated application and trafo melt the insulation and made short circuit between the windings (insulation for low temp).

All those answers can be found in dissasembling one broken transformer and will be clear what is inside. Dont be surprised to find wild windings style often found in modern (cheap?) trafos with bad insulation.

[Oddvar R]

It's 48 mm.

I put values in tables..with this dimension, it is possible to wind normal transformer (which will be in normal temp in use) with specs from datasheet - for 120VAC and 60 Hz primary. But for 230V and 50 Hz not, stack must be at least 55cm or lamination one size bigger (EI115-120).

So i didnt change my conclusion. If the temp is normal, can be clumsy wound.. if its too high temp, then primary turns are too low for dedicated application and trafo melt the insulation and made short circuit between the windings (insulation for low temp).

All those answers can be found in dissasembling one broken transformer and will be clear what is inside. Dont be surprised to find wild windings style often found in modern (cheap?) trafos with bad insulation.

Great info there, maybe not so strange Weber doesn't answer. What transformer would you suggest?

The first one I had, started smoking. I got 10% off the next one.

[Roe]

Great info there, maybe not so strange Weber doesn't answer. What transformer would you suggest?

try tube-town, for great value 50hz transformers

[martin manning]

Tube Town lists the same Hammond 290EEX as I linked at Mouser EU above at nearly the same price. Don't know about shipping cost.