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ark 3rd March 2004 11:13 PM

Using Telefunken "Tank" transfomers for a single ended el84 amp?
2 Attachment(s)
Dear friends,

I've got these Telefunken Power transformers - They weigh a ton!<br>One is marked 177v 0,4 A (whats a comma mean?) and 7.2V 20uA?

The other just: 6.3V 3.7A

I was wanting to use them for a little integrated single ended el84 style amp - like the decware zen se84cs.

I've already got some telefunken tubes and suitable output transformers....

Schematic here:

I am a complete beginner at these things but one (or both) of them ought to work. Right?

As best as I can figure out:

I need 6.4V secondary out for the heater circut on the input and output tubes.

???V AC secondary for the rectifier. then feed that back in to somehing for the ???Volt B+?

I read in the decware schematic above:
"Your B+ voltage should be between 320~350 vdc. The Bias Voltage on your output tubes should be between 9.5 ~12 vdc when refenced to ground."

I pretty much have everything but this transfomer worked out.
Only two sets of outputs... Ugh. Can advise to help make this match up in a simple way? Any Ideas if these transformers will be acceptable?

Thanks a bunch!!!

fdegrove 4th March 2004 12:48 AM



One is marked 177v 0,4 A (whats a comma mean?) and 7.2V 20uA?<br>
Strange figures...

177V 0,4A should mean .4A so 400mA
7.2V 20uA??? 7 Volt and 200 mV at 20 micro ampere? I wonder what that one's for...


The other just: 6.3V 3.7A
That would be the heater supply for god knows what...Useful to have anyway.


I need 6.4V secondary out for the heater circut on the input and output tubes.
6.3 V is pretty much the norm.


ark 4th March 2004 01:15 AM

Thank you for your input.
These were German military transformers I think?

"177V 0,4A should mean .4A so 400mA
7.2V 20uA??? 7 Volt and 200 mV at 20 micro ampere? I wonder what that one's for..."

I wonder too. I still vaguly understand this stuff but does this rating of 7.2V 20uA (7 Volt and 200 mV at 20 micro ampere) mean this transformer would be unsuitable for anyhting? the microampere measures how much power is allowed out?

Thank you.

analog_sa 4th March 2004 06:23 AM

I would go as far as suggesting you haven't read right the 7.2v rating. 20uA is so absurd as not to be even funny. 20mA?

ark 5th March 2004 02:06 AM

Please see the picuture. This is what I am trying myself to decipher.
It reads:


20uA (with a strange little backwards 'u' character someone here might understang but i don't.)

on the bottom I also see: 1500 Veff 50Hz 120V 50-60hz

What on earth would 177V 0,4A be good for?
This is a titanic looking tranny. Weighs a ton. much bigger than the 6.3v 3,7A one I have.

Thank you for you input! You all are great.

SHiFTY 5th March 2004 02:31 AM

In Europe, the role of a comma and a decimal point is reversed.

So you have a classy filament tranformer (6.3V @ 3.7A max) and B+ transformer (177V @ 400mA max) And even with the telefunken logo! With diode bridge rectification,you would be able to get ~240VDC with this, a little low but not too bad. With a voltage doubler type power supply and a tube rectifier, maybe 360V?

I don't know what the 7.2V @ 0.00002A would be any use for! :bigeyes: ("backwards u" = mu = micro = 1*10E-6 = 0.000001 or one millionth)

For the power supply, you will need to use a 6 volt heater tube rectifier with an indirect heater. On all the 5 volt rectifiers (5Y3, 5U4 etc), the B+ (high voltage DC) is taken directly from the filament, which is on their own 5V winding.

So use a 6-volt rectifier tube like EZ81 instead, and you can use your telefunekn filament transformer for all tubes in the amplifier. Or you could use a $2 diode bridge. :P

ark 6th March 2004 03:02 AM

ShiFtY is cool
thanks ShiFtY! Thats what I hoped to hear.
Thanks to everyone. I'll post pictures of the end result.

ark 8th March 2004 08:08 PM

2 Attachment(s)
So here is where I'm at now.

I have all the parts to assemble a se84cs like amp with a bunch of old telefunken parts... but I need to make these ol transformers work. I want a simple solution with a pretty telefunken tube or something like that.

Shifty says to use the big one with an EZ81 and a voltage doubler for the B+ then use the other straight? for a heater supply?

what exactly do i need to buy to finish this? I don't know how to make a voltage doubler.

someone want to scribble me a diagram to complete this? pleeese. :)

A Parts list anyone? :)

Thanks a bunch. I can't wait to finally get this hooked up and see some kinda fire and squonk.

You all are great.
anyone listen to Mark Kozalek?

fdegrove 8th March 2004 10:00 PM

2 Attachment(s)

Forget the EZ81...Even the best Telefunken can't perform a miracle.

You need some higher voltage and have 177VAC at 400mA available so: a voltage doubler using diodes is the easy way out.

You get about twice the volts at roughly half the current:

Cheers, ;)

P.S. Ignore the component values, I borrowed from an existing diagram.

ark 8th March 2004 10:42 PM

what parts would i need to make the voltage doubler?
i can't find any articles explaining how this works or how to construct one. I need specifics parts so i can order them up and glue em together. :)

thanks agian

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