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Using Telefunken "Tank" transfomers for a single ended el84 amp?

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Using Telefunken "Tank" transfomers for a single ended el84 amp?

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:

www.decware.com/se84cschematic.pdf

http://macjoejr.home.att.net/84c_kit/tranformerfolder/transformerlayout.html

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!!!
 

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diyAudio Senior Member
Joined 2002
Hi,

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.

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

177V
0,4A

7,2V
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.
 
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
 
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?
 

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diyAudio Senior Member
Joined 2002
Hi,

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.
 

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diyAudio Senior Member
Joined 2002
Hi,

Quote from Glassware:

The Voltage Doubler power supply configuration allows the creation of a power supply whose output voltage far exceeds the peak transformer secondary voltage. Two diodes, two capacitor--that's all there is to it. Only one half of the voltage cycle is used in each leg of this circuit, that is, one diode conducts, then the other--each builds up a voltage in its associated capacitor, which are in turn stacked one above the other, thus, doubling the voltage.

So what you need is 2 * 1N4007s , a cap of say 470µF/250VDC that goes inbetween the tiepoint of the diodes and finally another cap of say 47µF/400VDC to build your basic supply.

It will yield a voltage much higher than you require for the EL84s and the input tubes but at least you can now smooth further by either RC filtering or better still choke filters.

Keep in mind that the total current available is only half of what the xformer could have delivered without the voltage doubler.

Cheers,;)
 
Thanks. That's very interesting.
I have a filter choke someplace:
(CHICAGO TF1A04YY Filter Choke. 5HY 400ma. 60 ohm DCR)
Too big?

That will knock the voltage down a bit right?

I'm wondering now: where do I rectify to DC then?
Before or after the Diode doubler?

I still really want to use a tube rectifier if only for aesthetic reasons.
 
diyAudio Senior Member
Joined 2002
Hi,

That will knock the voltage down a bit right?

The 5H will be fine, bigger is even better but since this is what you have...

The 60 Ohm DCR won't bring the voltage down enough, you'll only need about 250VDC and you're looking at about 400VDC coming from the doubler.

Actually if you'd had about 10VAC more from the xformer a bridge rectifier would have worked fine....
There are tricks to add another xformer to the secondary but I'm no big fan of those stunts.

I'm wondering now: where do I rectify to DC then?

Reread the quote I pasted in the previous post; it's done...finito, simple as that.

I still really want to use a tube rectifier if only for aesthetic reasons.

Stick a candle on top of it...??
Seriously, do whatever you fancy but you can't have your cake and eat it too...so it's either the diodes as doubler or a totally different project altogether.
A preamp iso an amp for example, even so B+ will inevitably on the low side of good.

Cheers,;)
 
frugal-phile™
Joined 2001
Paid Member
For EL84s (better yet SV83s), i'd just bite the bullet and put a diode bridge on the 177V... you should get somewhere around 240 V -- maybe a bit low (you won't get quite as much power), but still fine. Use the choke in a CLC to get as little voltage drop as possible... the 6DJ8 will be more than happy with what you get.

dave
 
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