Help with OT

[spoontex]

Hi,

I need a pair of output transfomers for this project, but they don't tell the specs. It's a 30w push-pull amp. Anybody can help me?

thanks!

 

[huggygood]

Something like 5.6k UL 40 a 50 w should do the trick.
seems like an old pattern seen all over the place .

 

[LinuksGuru]

Any 30W 3.0 - 4.0K push-pull transformer with UL taps 20-40% will do the job.

 

[huggygood]

😆

 

[huggygood]

Write these values on a few balls, turn, predict and you will have your values.

 

[spoontex]

https://www.tube-town.net/ttstore/hammond-1650h.html?language=en

I don't find any 5.6k with 40 or 50w

 

[tikiroo]

The Mullard 5-20 has a similar looking output stage and uses either a 7k with 20% taps or a 6.6k with 43% taps for a Vak of about 400V.

 

[huggygood]

Something in the middle of it all will do.
and yes, it's 6.6k and not 5.6k (my tired eyes)

 

[spoontex]

https://edcorusa.com/collections/tu...w-6-6k-ohms-push-pull-tube-output-transformer

this one looks can fit.

 

[grovergardner]

Can we assume you have an oscilloscope and other tools for testing the amp? Any old transformer is not going to drop into the circuit without changing the feedback compensation networks. Without any changes the amp could be unstable.

 

[6A3sUMMER]

I do not see any Bleeder Resistor to discharge the B+ capacitor.
Ouch!
Prevent "The Surviving Spouse Syndrome".

Do not rely on the power tubes to discharge B+ capacitors, Because if there is something wrong with the output tube circuit . . .
Then YOU will be discharging the capacitors. Ouch!

 

[tomchr]

It looks like an EL34 output stage with ultra-linear (UL) taps. See the EL34 data sheet or google "EL34 UL transformer impedance".

Of course, looks like and is are two different things. The usual disclaimers apply.

Tom

 

[oemcar]

Hammond 1650 HA has single output winding which matches up to your schematic:

https://www.hammfg.com/electronics/transformers/classic/1608a-1650a?referer=790

I prefer the multiple windings of the 'H' version- I use second windings to power different speaker banks, instead of wiring together for single output...
But thats whole different topic
Jim

 

[jcalvarez]

Hammond 1650 HA has single output winding which matches up to your schematic:

I vote for that one too, using it on an Eico HF-89 variant, sounds very good.