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Old 27th March 2009, 08:21 PM   #1
newtube is offline newtube  United Kingdom
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Default 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-
Click the image to open in full size.

Click the image to open in full size.

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.
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Old 27th March 2009, 10:16 PM   #2
rkevans is offline rkevans  United States
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Default 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
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Old 27th March 2009, 10:32 PM   #3
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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.
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Projects: OTL-OCL 6AS7 Gen. Electric, SEs 2A3 RCA, 300B JJ, 6S4S, 4P1L, EL11 Telefunken, 6AS7 RCA, 6S33S, 6S41S, 6S19P, E84L Siemens, E236L Telefunken, headphone ampl. OTL Loftin White 6AS7 RCA,... PPs 6005 Gen. Electric, EL34 Mullard, 6L6....
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Old 28th March 2009, 03:41 AM   #4
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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.
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Old 28th March 2009, 08:27 AM   #5
newtube is offline newtube  United Kingdom
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Bugger. . .
Thanks for the info mate.

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

Cheers.
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Old 28th March 2009, 02:13 PM   #6
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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.
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Old 28th March 2009, 05:12 PM   #7
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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./
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