Why did my TX Burn out Help

pre65 · Post by **pre65** » Fri Mar 02, 2012 12:20 pm

Colin, how many ma do you need ?

colin.hepburn · Post by **colin.hepburn** » Fri Mar 02, 2012 12:47 pm

Don't know really it depends on what valve I want to use like EL34 5881 6L6 or 807s and how hard I want to drive them at

A new TRA 400 TX was intended to be use across different amps and valve types As I can't afford to buy a Main TX every time I want to build an amp
that's why I took the TX to be 200mA CT or 400mA in parallel which would have covered most

Paul Barker · Post by **Paul Barker** » Fri Mar 02, 2012 12:49 pm

colin.hepburn wrote:Here's the extract form the email Ask Jan sent me his words not mine I was under the impression each winding was 200mA giving me 400mA in parallel but it appears not
Jan said
The current rating of the transformer (200mA) is for ohmic load ac
given, this is how its done in Germany.

I know that the Amercians rate the transformers as DC after the
rectifier. Which means that 200mA AC result in about 120mA DC rating.

Please take care of this.

It is quite unclear, but what I am interpreting this to mean is that with your various secondaries all joined and full wave rectified your DC output must not exceed 120mA total, and that leaves nothing for filaments.

Transformer not very powerful therefore.

ed · Post by ed » Fri Mar 02, 2012 12:54 pm

Nick wrote:I may be missing something, but I assumed that the winding rating was a measure of the current the winding will supply. They can't assume what follows, it might be a full wave reg, it might be a voltage doubler and so on.

I normally use the equations on Sowters site

http://www.sowter.co.uk/rectifier-trans ... lation.htm

There will always be international interpretations of the same thing. I believe it's just the way these things are presented that causes dificulty......

e.g here is the Hammond equiv of the sowter doc.....hammond chose to make x the missing variable to be calculated, because we know all the other details...Sowter chose to make x a variable we already know from the transformer spec, and approach the problem from the point of view 'this is what I want so which transformer fits'.......

re the ask jan spec, the rating seems well explained in the red section at the top of the transformer page....I might be misunderstanding, but are we saying this is wrong?

ed · Post by ed » Fri Mar 02, 2012 1:29 pm

Colin,

does this help?:

http://sound.westhost.com/xfmr2.htm#s8

colin.hepburn · Post by **colin.hepburn** » Fri Mar 02, 2012 1:30 pm

I really do not understand this is all double Dutch never mind German each post is making this more complicated I am not referring to heated filament just the HT
If we buy a Hammond 200VA} TX 640CT@200mA DC we take that to be the true current 200mA
So here is the spec for the Ask Jan coped from his site http://www.die-wuestens.de/eindex.htm
200 VA
Secondary's:
2*270 V 0,2 A
2* 50 V 0,2 A
6,3 V 2 A
5 V 3,5 A
6,3 V 7 A

B+ secondaries can also be connected in parallel for use with a rectifier bridge. The 50 V secondaries can be used for biasing or in series wit hthe 270 V secondaries to get a 320 V plate supply.
Right so I am thinking its 200mA same as the Hammond so looks like a reasonable usefully TX until he said the 200mA is AC making this TX only 120mA DC i don't get this

Paul Barker · Post by **Paul Barker** » Fri Mar 02, 2012 2:25 pm

Yes that's it. It's 120mA DC.

pre65 · Post by **pre65** » Fri Mar 02, 2012 2:34 pm

Colin, if you don't need a 5v winding (for rectifier) you might like to look at the Antek range of toroidal transformers.

http://www.antekinc.com/

They come from USA but even with shipping they are good value.

I've got 5 of theirs (so far) and they are well made.

PS

the voltage is per winding so 400v is two 400v windings and could be 800v with a centre tap.

pre65 · Post by **pre65** » Fri Mar 02, 2012 2:44 pm

Something like this perhaps ?

http://www.antekinc.com/details.php?p=710

Two 320v secs at 630ma each and two 6.3v secs at 4A each.

I think that would meet your requirements.

And it's $57 (US dollars) + shipping.

Mike H · Post by **Mike H** » Fri Mar 02, 2012 3:28 pm

colin.hepburn wrote:200 VA
Secondary's:
2*270 V 0,2 A
2* 50 V 0,2 A
6,3 V 2 A
5 V 3,5 A
6,3 V 7 A

I could be wrong, and I hope not else the way I've been thinking about it for years is all wrong, but to me that says e.g. 270V AC r.m.s., and 0.2A r.m.s., multiply by 1.414 for peak values

Although ideally you probably wouldn't want to run it flat out all the time, hence I can see the logic of 120mA max. as a 'safe region'

2 in parallel, 240mA

But, you're running EL34 and suchlike single-ended, so I can't see two amps in stereo being too much over 100mA total, going by your descriptions of it so far

Incidentally, if you are using this to power 2 off of these SE amps, why not use a separate 320V winding for each amp? Just because you can

pre65 · Post by **pre65** » Fri Mar 02, 2012 3:35 pm

My 832a PP amp needed a 200v transformer, so I got a 200v antek and used one 200v secondary for each channel.

Works a treat.

colin.hepburn · Post by **colin.hepburn** » Fri Mar 02, 2012 4:09 pm

Mike H wrote:
colin.hepburn wrote:200 VA
Secondary's:
2*270 V 0,2 A
2* 50 V 0,2 A
6,3 V 2 A
5 V 3,5 A
6,3 V 7 A
I could be wrong, and I hope not else the way I've been thinking about it for years is all wrong, but to me that says e.g. 270V AC r.m.s., and 0.2A r.m.s., multiply by 1.414 for peak values

Although ideally you probably wouldn't want to run it flat out all the time, hence I can see the logic of 120mA max. as a 'safe region'

2 in parallel, 240mA

But, you're running EL34 and suchlike single-ended, so I can't see two amps in stereo being too much over 100mA total, going by your descriptions of it so far

Incidentally, if you are using this to power 2 off of these SE amps, why not use a separate 320V winding for each amp? Just because you can

Yep mike I see your points

But when using the KT66s for example I have an idle current of 55mA x2=110mA plus 6SL71.5mAx2 =3mA I think so total ide current 113mA

The ask Jan TX was wired CT full wave given me 400vHT@200mA or so I thought but in reality is was only 120mA so a safe working point would be say 60/70mA I had a 113mA on it
Same for parallel 240mA yes but safe use would say 100/110mA so I see this as not man enough

Mike H · Post by **Mike H** » Fri Mar 02, 2012 4:55 pm

N-no, 113mA is still less than 120mA, so, should be OK?

Even if it were full-wave, 320 - 0 - 320 @ 200mA

colin.hepburn · Post by **colin.hepburn** » Fri Mar 02, 2012 4:58 pm

pre65 wrote:Something like this perhaps ?

http://www.antekinc.com/details.php?p=710

Two 320v secs at 630ma each and two 6.3v secs at 4A each.

I think that would meet your requirements.

And it's $57 (US dollars) + shipping.

yep seen these on ebay as well that looks good about £67 quid with shipping then

colin.hepburn · Post by **colin.hepburn** » Fri Mar 02, 2012 5:09 pm

Mike H wrote:N-no, 113mA is still less than 120mA, so, should be OK?

Even if it were full-wave, 320 - 0 - 320 @ 200mA

no but its at 320-0-320@120mA not 200mA thats what i am trying to say the German way for some reason is calculated AC current not DC

current you wouldn't want to run a TX that close to it limits would you

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