irkutsk: Temperature of mains transformer

Hello!

I have one Rekord 53 from the Berdsk Radiofactory that had a completely burned power transformer as I got it.

I now got one made in Irkutsk with a good looking transformer.

I replaced some bad components on that chassis and it is working fine now (at 220V from isolation transformer). All voltages are as shown in the schematics.

Problem is the power transformer gets hot. After like 20 minutes it has 75°C on the bottom and the wax is melting...

Could someone who owns one of these please check the temperature on his device?

I'm just curious if this is normal or if I have another failed transformer.

 

regards

Markus Zluwa

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Ave!

75°C is too hot. Could you check primary current, and then with 6Ц5С removed? Maybe there is problem with mail filter capacitors? Have you checked them? If the transformer will get hot after tubes was remowed it may be cused by interturn short circuit. If ths happen the transformer should be rewound.

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I had checked the power consumption of the whole device which was ~130mA@220V which would be OK for that device.

But... with no tubes or dial lamps it already draws 90mA@220V.

I will check for some unwanted connections once more later but I guess this is another failed transformer.

Maybe I'm just in bad luck or these factories really made some crappy transformers back in the day...

I can not wind transformers and this device is not worth the money to pay someone to do it. I will just dig through my stash and put another transformer in.

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Some mains transformers are indeed quite tightly dimensioned. If these are designed for 220V, the magnetising current then rises relatively steeply at 235V. Compare the examples in "Mains transformer magnetising current: increase at 235V".

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Manche Netztransformatoren sind in der Tat ziemlich knapp dimensioniert. Wenn diese für 220V ausgelegt sind, steigt der Magnetisierungsstrom bei 235V dann relativ steil an. Vergleichen Sie hierzu die Beispiele in "Netztrafo Magnetisierungsstrom: Anstieg bei 235V".

MfG DR

 

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As neither me nor the guy that sold the radio to me powered it on at normal mains voltage I guess this is more likely a failure of the insulating materials used in these transformers.

The device was unused for decades from its look.

But good to post this in here Mr. Rudolph as this is really a big problem.

I had checked everything twice and even tested the transformer after removing it from the chassis which made no difference. It has some shorted windings.

I have found a slightly larger transformer with useable output voltages and currents and a 240V rated primary that I will use now. Not original but good enough for a 20€ radio and it will look like someone repaired it back in the 1970s in the GDR.

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