Phonoland

specifically testing transformer on a 1426 rockola.
it uses a 5u4g rectifier tube.
what should ohm readings be on pins 4 to ground, 6 to ground?
also pins 2 and 8?

i basically have 55 ohms on 4 to ground
60 ohms on 6 to ground
115 to 120 on 4 to 6.

pins 2 to 8 read .1 to .3 ohms? is this normal?

thanks

George

I can't speak of that specific machine, but based on standard connections to a 5U4 the 2&8 are the filament winding and thus very low impedance

Pins 4 & 6 should have approximately the same reading to the center tap which goes to chassis ground. A dozen, or so ohms either way is to be expected on older transformers.

Based on your readings I'd pronounce the transformer OK and ready for a careful power up.

Do check for excessive leakage to chassis ground by measuring from the chassis to an outlet ground. reverse the plug and read again. You probably will see some leakage but it should not be enough to cause a short if the chassis is then grounded and should essentially go away if a 1 megohm resistor is connected between chassis and external (outlet) ground.

Rob/NYC

Thanks for info Rob, will proceed with caution.

Another question, this amp calls for a 1000ohm 10 watt
Candohm resister. Can I use a 1000ohm 10 watt
Wire wound resistor in its place?

Is the candohm just an outdated type of
Resistor or did it have a more specific function.
They're hard to find.

George

Raven,
Do a web search--lotza info on them--- Ron Rich

George, in a word "yes". In a few more words, there is noting special in these old amps -just arcane and obsolete. Replace it with similar value(s) on a terminal strip.

Rob