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Author Topic: 807  (Read 678 times)

Apocalypse Boy

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807
« on: April 22, 2011, 05:39:39 pm »
So I picked these up today....I've spent R200 on a lot less :)





Now the problem starts.

5 of the 807 are NOS'ish, they look in good shape, the other 3 are a bit miff, but good for testing, So I blow them up.....Big Whoop.

The Tranny is where I'm stumped. It's marked at 15W....REALLY....It's huge. I tested the primary ( Labled 10000 Ohm) at 219 Ohm, Weird or am I a Banana.

Do you guy's know more about these , they are Savage Transformers, England, Code : 2B36B.

PS. I got a WHOLE lot of Octal chassis mount bases and a WHOLE lot of other valves with it, will post some pix later )
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ludo

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Re: 807
« Reply #1 on: April 22, 2011, 06:26:48 pm »
Bigger core is better. In output transformers especially. The 10k Ohm is the Impedance of the primary when loaded by 8 ohm (or whatever it is specced for) on the secondary. Your meter measures only the Resistance of the winding at DC, not the reactive component at audio freq.

Pretty. Very pretty. And I'm sure it will get prettier :)
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Jazzy

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Re: 807
« Reply #2 on: April 22, 2011, 06:38:26 pm »
Got excited when I saw the 2 valves on the top left corner, thought it was the RCA 76 type...
Looking for a pair!
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Family_Dog

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Re: 807
« Reply #3 on: April 22, 2011, 06:42:50 pm »
Pretty,... very pretty!   :)


-F_D
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Apocalypse Boy

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Re: 807
« Reply #4 on: April 22, 2011, 09:28:45 pm »
Gents

Thank for the reply.

@Jazzy

Not sure what there is, but 75's ring a bell, there are some 80's I know....And in keepimg with the forum, If you have a task for them, They are you'rs....For free :)

@ludo

They measure that no matter what.... If I compare them With the numbers I have for my EL34's....5 times the size. I'll make it too Pretty :)
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Ampdog

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Re: 807
« Reply #5 on: April 23, 2011, 01:35:20 am »
A B,

I thought for a moment that the transformer was for a Williamson amplifier, but that would have had 8 secondary sections instead of 5. Savage was one of the top British transformer companies of the time. I tried the number but there is no reference to it any longer.It could still be used with p.p. EL34, KT66, 6L6GC. Pity there were not two units!
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Apocalypse Boy

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Re: 807
« Reply #6 on: April 23, 2011, 07:58:57 am »
Quote from: Ampdog on April 23, 2011, 01:35:20 am
A B,

I thought for a moment that the transformer was for a Williamson amplifier, but that would have had 8 secondary sections instead of 5. Savage was one of the top British transformer companies of the time. I tried the number but there is no reference to it any longer.It could still be used with p.p. EL34, KT66, 6L6GC. Pity there were not two units!

There are two :) . I just dont know how to configure the secondaries, was hoping for some info but my web search has come out empty thus far. I wonder how much one can get out of these, the 807's in PP might be a bit much for it
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handsome

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Re: 807
« Reply #7 on: April 23, 2011, 09:17:07 am »
you (briefly) apply mains voltage to the primary and measure the resulting voltage on the secondaries, thus establishing the voltage ratio from primary to secondary. from that you should be able to work out the rough impedance of the secondaries. you know that the primary is a 10k impedance (it says so) so you can work backwards to find out the secondary impedance. the turns ration is: mains voltage (on primary) / secondary voltage. the impedance ratio is this ratio squared. the secondary impedance is therefore the 10k divided by the impedance ratio. it appears there are several secondaries and they can be paralleled or seriesed or a combination of both to get 4R, 8R and 15/16R.
dont apply the mains for too long as it may saturate the transformer due to the low frequency (50Hz) and large signal (220V) which will give you inaccurate results.
also make sure you measure the mains as well at the time to get an accurate calculation.
measure the resistance of all the secondaries to establish which are connected to which.

@jazzy: very, very nice tube the 76, what are you planning to use them for?
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Schalk

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Re: 807
« Reply #8 on: April 23, 2011, 09:26:37 am »
And on the mention of the venerable 6L6 series....

http://youtu.be/aHimn20w32I
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Jazzy

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Re: 807
« Reply #9 on: April 23, 2011, 09:34:47 pm »
@ Apoc Boy
Thanks for the generous offer, unfortunately I do not have a use for the 75 & 80s
@ Handsome (feels weird calling you that)
I use a pair of RCA 76s in the input/1st gain stage of my SET amp, I do have a spare set but they are not as quite (slight hiss) as the main set.
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handsome

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Re: 807
« Reply #10 on: April 23, 2011, 11:43:08 pm »
@ jazzy: i lashed up a channel of a 300B SET once with a 76 feeding an 85 and it sounded magnificent. mine was modification of the JE Labs design. i have noticed 76s are now not as easy to get as they used to be about 6 years ago, i never realised this tube was so popular.
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Jazzy

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Re: 807
« Reply #11 on: April 24, 2011, 06:13:15 am »
Yep, the 76s are now more than $50 a pair if you can find them new! Used / loose ones are not a problem.
Don't know much about the 85s, I'll read up on them. So what happened to your 300B amp?
Mine goes 76 > 6J5 > 300B > 572-10 (interstage transformer between the 300B and the 572-10, similar to Andy Grove's Audionote Ankoru design, in fact using the same transformer)

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handsome

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Re: 807
« Reply #12 on: April 24, 2011, 08:44:54 am »
what happened to my 300B was the usual laziness/procrastination. The latest (ahem) plan is to use the 76 feeding a 31 which is a DHT originally intended for battery use so low filament current & voltage. but i do have a lundahl interstage and a couple of 5842's as well....which was the last plan.
the 85 has a mu of 8 & Ra of ~8 - 10k sort of a low gain 6J5 - they very cheap and have the ST bottle with grid cap. I used it cos i didnt want too much gain in the power amp and it matched the looks of the 76.
what kind of heater/filament arrangements do you have on your amp? and how much hum do you have? also do they still make SV852-x/SV811-x? I had heard that they stopped.
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Apocalypse Boy

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Re: 807
« Reply #13 on: April 24, 2011, 08:45:52 am »
Quote from: Jazzy on April 23, 2011, 09:34:47 pm
@ Apoc Boy
Thanks for the generous offer, unfortunately I do not have a use for the 75 & 80s
@ Handsome (feels weird calling you that)
I use a pair of RCA 76s in the input/1st gain stage of my SET amp, I do have a spare set but they are not as quite (slight hiss) as the main set.

Oops, I read 75, Not 76 :)
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Apocalypse Boy

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Re: 807
« Reply #14 on: April 24, 2011, 09:08:03 am »
Now for the next stage, I'm looking for some bases, 4-pin (for the 80's) and 5-pin and top caps for the 807. I have a bag full of octals ( 30 + ) to swop :). I know mr Valve has, but dont want to spend 100's on bases for just testing now
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