5y3gt tube turns red

Hello

I've got some troubles with my tube amp
The 5y3gt turns red even when i remove all the other tubes
the 5y3 stays red
Is the tube broken or is the someting else?

Please help!!

5Y3 is a rectifier tube. If it glows red, you've got a short circuit somewhere after the tube or the tube itself has an internal short circuit. In both cases it should be possible to measure this short circuit.
Have you checked the filter capacitor after the tube?

Hello timroy

A red-hot rectifier tube indicates an excessive current draw. Your amp should be repaired by a professional if you do not even have the necessary knowledge. You should no more turn on the power until the fault has been corrected, otherwise the tube and additional components can be damaged.

Best regards - charly49

I replaced al the the caps and resistors as Always
So i thought that can't be the problem
I thought that the tube was bad
But gues what,the new filter cap after the the tube was bad
I thought that they didn't make bad caps anymore

Who has the same problems with new caps?

Hello timroy

New electrolytic capacitors are usually not bad. But it must be observed different things, so they are not destroyed. This is one of the reasons why I always advise not to perform such work itself if the expert knowledge is lacking.

Incorrect polarity of the applied voltage will destroy the electrolytic. This can happen if the capacitor is installed incorrectly or if the rectifier tube is shorted. The applied voltage must never exceed the rated voltage. This can happen if the load is too low. The power tubes take longer to heat up than the rectifier tube, so the voltage is initially much higher. The same happens when you remove the tubes. For very old amplifiers (I think, yours with 5Y3 is a very old), it is also important that the field coil of the speaker is connected (and not interrupted), otherwise the voltage is also increased. Electrolytic capacitors that were on stock for many years, must be reformed before they are used. This means that they must be charged for a long time with limited charging current.
There are further things, such as temperature and ripple current, which must also be observed, so that the capacitor is not destroyed.

Best regards - charly49

Thank you

For example for a 63v cap i use a 100v cap
so this can't be wrong

High voltage electrolytic capacitors are sold not so often. So, if you buy them in regular electronic shops, that are not specialised in tube or vintage equipment, it's not a bad idea to reform the capacitors. It's possible that the "new" ones have spent a few years on the shelf.

Hello timroy

Install a 100 volt capacitor instead of a 63 volt is certainly not wrong. Filter capacitors have neither 63 nor 100 volts, but at least 450 volts. In many cases this is still not enough, even though the voltage is only about 400 volts during operation. For the reasons already mentioned, the voltage can initially be much higher. The old caps could withstand this for some time, but often not the modern (and cheap) ones. I therefore use only high quality components with suitably high values. The repair costs are, even though I use expensive components, not very high, because I renew only the components that are really defective.

Best regards - charly49

Anyway i bought a new filtercap(500v)
from a guy that repairs stage tube-amps
Repalces the filtercap and the 5y3 tube to make sure
and eveything works great again
The guy said the same thing that my (new) filter cap was not used for a long time