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-   -   Mains transformer help needed please (http://www.diyaudio.com/forums/tubes-valves/141303-mains-transformer-help-needed-please.html)

newtube 27th March 2009 08:21 PM

Mains transformer help needed please
 
Hi guys, this is my first post after lurking for a while :)

I'm collecting the parts for one of Georges simple se amp boards and i could do with your help on transformers. . .
I have these as output trans-
http://i20.photobucket.com/albums/b2...nce300BOPT.jpg

http://i20.photobucket.com/albums/b2...TSchematic.jpg

they are from a consonant 300b set amp and the only thing i know about them is they are single primary winding, no ul tap and are 60-70ma.

I'm going to be using them with 6l6gc (chinese) in a simple se amp.

Would this mains trans be suitable-
http://cgi.ebay.co.uk/Hinchley-Vinta...1%7C240%3A1318

ANY help is apreciated,
Cheers
Darran.

rkevans 27th March 2009 10:16 PM

Re: Mains transformer help needed please
 
Quote:

Originally posted by newtube
Would this mains trans be suitable-
ebay link to: Hinchley-Vintage-Power-Supply-Transformer-Valve-Amp
ANY help is apreciated,
Cheers
Darran.

Almost suitable.

5.0V @ 2.0A for rectifier (Need 1.9A for a GZ34) -- OK.
6.3V @ 3A (Need 0.9A for each 6L6GC) -- OK
6.3V @ 3A
380 - 0 - 380 @ 100mA (Need about 150 mA here) -- Not enough current for a Simple SE board. Voltage is about right.

Sorry,
Rick

azazello 27th March 2009 10:32 PM

You can use this output transformer with 6L6, but only in triod mode
/Ri=apr. 1,2 kom with transf. 3,5 kom !! OK!/, with Ia=40-45 ma.
You must connect Grid2 and plate with resistor 200-300 ohm.
And You can use this main transf. only with rect,, GZ34 ! I don't
prefer You with rect. diodes. /90 ma for 2 x 6L6, and 10-15 ma for
preamp. ECC85, 81, 82, 80...for both channels /. /Pa each 6L6 = 415 v after rect. x 40-45 ma = 18,67 wts....OK!/.
Don't worry if You adjust Ia=50 ma for 6L6 and Ia=7-8 ma for preamp triode for each channel ! I= 120 ma it's OK /20% more - OK!/ for both channels.

boywonder 28th March 2009 03:41 AM

Quote:

Originally posted by azazello
You can use this output transformer with 6L6, but only in triod mode
/Ri=apr. 1,2 kom with transf. 3,5 kom !! OK!/, with Ia=40-45 ma.
You must connect Grid2 and plate with resistor 200-300 ohm.
And You can use this main transf. only with rect,, GZ34 ! I don't
prefer You with rect. diodes. /90 ma for 2 x 6L6, and 10-15 ma for
preamp. ECC85, 81, 82, 80...for both channels /. /Pa each 6L6 = 415 v after rect. x 40-45 ma = 18,67 wts....OK!/.
Don't worry if You adjust Ia=50 ma for 6L6 and Ia=7-8 ma for preamp triode for each channel ! I= 120 ma it's OK /20% more - OK!/ for both channels.


But you would have zero headroom left for any transients, and may risk overheating the transformer and shortening it's lifespan. If you already owned this, perhaps you could experiment, or if you had a pair, you could build P2P monoblocks, but you are designing yourself into a bit of a corner.

I would also imagine that you may want to experiment with other tubes and other configs than triode 6L6's (like KT88's running "hot").

If it were me, I'd find a transformer with more ma.

newtube 28th March 2009 08:27 AM

Bugger. . .
Thanks for the info mate.

I don't suppose anyone can point me in the right direction for a suitable one?

Cheers.

boywonder 28th March 2009 02:13 PM

Quote:

Originally posted by newtube
Bugger. . .
Thanks for the info mate.

I don't suppose anyone can point me in the right direction for a suitable one?

Cheers.


Keep looking on ebay, the trading post here, or pick up the recommended Allied P/N that Tubelab George recommends from Mouser or Digikey or a new Hammond from Angela Instruments, Antique Electronic Supply, etc. Since you are across the pond the US suppliers may be cost prohibitive due to shipping

There is also no downside to posting a wanted-to-buy ad in the trading post.

You can always start assembling everything else while you continue to troll for a suitable used one if that's your fancy.

azazello 28th March 2009 05:12 PM

Thanks for the info mate.

I don't suppose anyone can point me in the right direction for a suitable one?


Newtube,
I'm sure what I talk....but the choice is Yours..../All main transf, have
reserve min. 10 -20 % for normal work....I've used output transf.
Hammond 125 FSE - 90 ma whit GU50- 150 ma for some days and transf. worked OK without preheating. All good firms produce transformers with 20-30-50% more quality./ :cheers:


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