Transformer for Tube Amp - Gold or Junk?

[Shadetree Mechanic]

We are dismantling an old production line at work, and one of the pieces of equipment had these neat transformers. They are step down to provide power to control circuits and motor power. They have a 600v primary and I was wondering if I could power the secondary with line voltage to use as a step up transformer? Even the little one is heavier than it looks.

 

[Shockwave]

You can use any tap as a primary as long as you do not apply more than the rated voltage or, draw more current than that winding is rated for.

 

[nomadradio]

A step-down transformer makes a perfectly-okay step up transformer. It won't care.

73

 

[Amperex]

600 volts powers 30 to 40 watt plate sweep tubes.

 

[Cable Guy]

Id venture a guess of gold to folks like us, probably scrap price to the average Joe (assuming copper, and not copper-clad alum windings).

 

[nomadradio]

600 VAC into a bridge rectifier circuit will get you about 850 Volts DC. Might be safer to use the 550 tap and be happy with about 820 VDC. A pair of 450-Volt electrolytic filter caps in series will be happier at 820 than 850. General rule is not to apply more than 9/10 of the rated voltage to electrolytic caps with no load. The bleeder resistor across each of two caps will set how the voltage is evenly divided between them. Unless you use 1 percent-rated bleeder resistors, the 90 percent rule tends to make filter caps last longer. If they don't split the voltage in an even 50/50 one of them could get more voltage than its rated to take.

73

 

[nomadradio]

scrap price

I scrapped a literal half ton of old transformers a few years back. The scrap guy said they're classified as "motors" at 50 cents a pound. Wasn't profitable, but it got them out of the way.

73

 

[unit_399]

Great looking shop. Love the polished concrete floor.
-J. J.