4v for rectifier tube

[camotecue]

a silly question: what will happen if i use a 4v supply for a 5v specified rectifier like a 5y3 or 5u4g tube?

larry

[Sheldon]

You can probably get away with it, but only if you are drawing well under the maximum current for the tube.

Sheldon

[camotecue]

thanks.

[Miles Prower]

If you under power the filament of a power diode, you will lose Isurge capability, and increase Vf. It's not a good idea, especially if your design is bumping against the max ratings.

It'd be better to get a proper filament xfmr for the type.

[sorenj07]

A small 5V 2A transformer (only 10VA) is worth it for a 5AR4/5Y3 type.

[camotecue]

thank you guys. i better ask my winder for a new transformer.

[kevinkr]

Originally posted by camotecue
thank you guys. i better ask my winder for a new transformer.

Or possibly use a 4V rectifier tube... (Some rare German and English types, look on eBay)

[Sheldon]

Originally posted by camotecue
thank you guys. i better ask my winder for a new transformer.

If you are not pushing the rectifier to its current limits, don't worry, try it. Your 4V winding may give you something a little higher than 4V, and virtually all tube are rated at least +/_ 10%, so 4.5V on the filament would be within normal rating anyway. You don't have to try your best tube - 5U4G's are cheap and readily available.

Sheldon

[Geek]

A pair of unloved 3V damper tubes with resistor in the heater would also work if you're concerned.

Cheers!

[Klimon]

You don't have to try your best tube - 5U4G's are cheap and readily available.

Better not to use it; 5u4g has excessive heater current draw (3A vs. 2A for e.g. gz32 and gz34) which will further decrease your voltage under load.

Simon