Transformer specs

[macula56]

is it possible to find out the amperage specs for a power tranny without having a model # to reference?

[FYL]

You can guesstimate them by looking at the core size, measuring windings Rs and output Vs.

For example if you measure 5.7 V unloaded at a YEL/YEL winding, you can be pretty sure it's a 5 V. If R = .5R or so you can presume it's probably sized for 2 A, if R < .25R it's a 3 A or more.

[macula56]

thanks FYL.  i am more concerned about the overall amp rating and the 6.3 filament tap.

[PRR]

Look at Hammond's tube-type transformers, find something of similar weight and width. Your unit will probably have a similar Total VA.

The balance of VA between HV and heater windings is not fixed, true. But if you are looking at POWER amp supplies in the 250V-500V DC range, there's a strong trend. Plate power will be significantly more than total power-tube heater power and somewhat more than total preamp/poweramp heater power. (If looking at 120V plate supply, you can't get much Power until you go to big cathodes which means big heaters and heater-power greater than plate power.... that's why we like to work at 250V and up.)

[FYL]

i am more concerned about the overall amp rating and the 6.3 filament tap.

Same method: guesstimate according to the core size, then measure the filament winding.

[RicharD]

You can measure the unloaded secondary voltage and them measure the primary DC resistance and plug the data into Duncan's PSU Designer II and it'll hazard a guess for you.  Ultimately once the circuit is built and loaded, measure the secondary voltages.  If there is excessive voltage drop or the transformer is getting too hot to touch, you're overloaded.  I'm guessing you have a "total" mystery transformer.  If you have something hijacked out of an old PA or whatnot, look at the previous tube complement and try to stick to something around that current draw.

[macula56]

it's not a mystery transformer. it's the PT in my Route 66. they come with an EF86 and a 12AX7A but the chassis has holes for 2 more tubes. i was wondering if the PT would support 2 more tubes without problems. as expected the good Dr. is not giving me that info.

[FYL]

it's not a mystery transformer. it's the PT in my Route 66. they come with an EF86 and a 12AX7A but the chassis has holes for 2 more tubes. i was wondering if the PT would support 2 more tubes without problems. as expected the good Dr. is not giving me that info.

The original Route 66 used a Cin-Tran 3439, built to Mike Z. specs. Really good iron, well sized, OK with two more preamp tubes drawing 300 mA ea.
Dunno about the current version.

[macula56]

thanks FYL. i haven't opened it up yet to look at anything. i like the way it sounds but i would like a little extra clean as well.