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Old 7th Mar 2018, 4:36 pm   #1
rsedwards1
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Default Partridge Transformers

I have acquired these Transformers one is Mains and the other is Output anyone recognise what these was for or what Amplifier has them
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Old 7th Mar 2018, 6:19 pm   #2
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Default Re: Partridge Transformers

They look seriously industrial-strength.

What are the ratings on the secondaries? [photos are indistinct].

Don't assume they were intended for an amplifier - they could just as easily have come from a 1950s/1960s private-mobile-radio VHF 'base-station' two-way-radio transmitter/receiver, an amateur transmitter/modulator or similar.
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Old 8th Mar 2018, 7:43 am   #3
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Default Re: Partridge Transformers

Nice C core tfmr's but the secondary HT is a bit mad for your average OP valves - is that 500 450 0 450 500? That'll give you over 1400v solid state rectified.

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Old 8th Mar 2018, 8:48 am   #4
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Default Re: Partridge Transformers

Didn't the Williamson Amp use 450-0-450 ?
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Old 8th Mar 2018, 9:26 am   #5
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Default Re: Partridge Transformers

I think mine is 400-0-400 but perhaps a KT88 / PX25 version?
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Old 8th Mar 2018, 9:46 am   #6
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Default Re: Partridge Transformers

The EL34 datasheet indicates operation with HT voltages of 500-800V (!) for the highest output powers.

Cheers,

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Old 8th Mar 2018, 10:18 am   #7
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Default Re: Partridge Transformers

I have a Philips 70watt amp here that has 2xEL34 in push pull with 800v HT derived from a voltage doubler circuit with two AX50s. Stand well back! The amp cover and chassis is made from a die cast alloy, so any explosion is contained
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Old 8th Mar 2018, 10:35 am   #8
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Default Re: Partridge Transformers

The presence of taps for two HT voltages is interesting. 450-0-450 is still too high for drivers and early stages.

Fitting with the AM base-station transmitter suggestion, they could be for a choice of two transmitter output powers. Licences came in all sorts of power levels for different areas of coverage and such transmitters had arrangements to set the max power. Alternatively, the two different HTs could be used for PA and modulator. If the transformer happens to have two well insulated 5v secondaries for rectifiers, that would be a clue that both voltages were in use at once.

Those are very high quality transformers, and there isn't often the budget in hifi amplifiers to afford them. Factory PA, ditto. Some user who wanted serious reliability and had the funds to pay for it... Aviation ground transmitter? They have back-ups and still go for top quality. The military would have stock numbers all over them.

The ratios of the other transformer would give clues about what it's to do.

To get any further needs either photos with the markings all legible, or else a diagram.

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Old 8th Mar 2018, 11:13 am   #9
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Default Re: Partridge Transformers

Quote:
Originally Posted by G6Tanuki View Post
What are the ratings on the secondaries? [photos are indistinct].
I have just measured the windings and have made a drawling up in paint see pictures
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Old 8th Mar 2018, 12:48 pm   #10
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Default Re: Partridge Transformers

The noted numbers appear to be factory build sequence numbers - Partridge sometimes show them for what seems to be commercial batches to equipment manufacturers. I've seen sequential numbers applied to the power, output and choke parts of an amplifier for one manufacturer (the parts typically also have known model numbers such as WWFB for Williamson output).

However the meaning of the letter at the start is certainly not clear to me after looking at many transformer examples. So far I have seen them as one letter then four numbers (and sometimes with another letter at end) - and have photos of examples with C, D, F, G, H. Some of the commercial model ranges are also one letter and then 4 numbers (eg. the P range of output transformers).

That power transformer is similar to the H500/350T in the 1965 catalog. It's a nice rating for a sizeable power amp, given the bias winding, and separate windings for B+ and screen supplies.

The turns ratio of the output transformer would need to be measured to guess the likely impedances.

Last edited by trobbins; 8th Mar 2018 at 1:01 pm.
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Old 8th Mar 2018, 1:21 pm   #11
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Default Re: Partridge Transformers

May last drawings have made a mistake got them in wrong diagram i have re done these
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Old 8th Mar 2018, 1:35 pm   #12
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Default Re: Partridge Transformers

The mains transformer looks like it could usefully power up a Radford STA100 clone. Whether the output transformer would suit remains to be seen- what are its turns ratios?
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Old 8th Mar 2018, 5:11 pm   #13
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Default Re: Partridge Transformers

2 5v windings would suggest 2 rectifiers which would tend to date the power transformer to late 50ies or early 60ies, when C cores took over. Early VHF transmitter base stations (PYE F27 for example) used Laminated cores with single HT windings for a semiconductor bridge built onto an octal base [465v]. Earlier military systems used standard E & T lamination's which produced larger and heavier units. The attached example shows an admiralty transformer with 2 heater windings to take advantage of the tapped HT secondary.

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Old 8th Mar 2018, 5:57 pm   #14
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Default Re: Partridge Transformers

Quote:
Originally Posted by Diabolical Artificer View Post
Nice C core tfmr's but the secondary HT is a bit mad for your average OP valves - is that 500 450 0 450 500? That'll give you over 1400v solid state rectified.
er no Andy, you'd theoretically get 630 or 700v, using the CT for 2 diode use.

Which might be ok to run a KT88 at, but i wonder if the modern varieties are as robust as the original MO/GEC jobs?

be ok for a 211 or 813 though.............. if you are mad enough and have a fair bit of disposable cash.

If you valve rectified with something like a 5U4G etc you would likely get a usable HT for something like a KT88, should you really wish to do such a thing.

I guess a few years ago there would be a fair few Amateur radio enthusiasts interested in 'em?
A.
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Old 8th Mar 2018, 6:24 pm   #15
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Default Re: Partridge Transformers

Hi all,
The power tx would certainly suit the GEC 88/50 in their grey book as that requires 500V HT.
I have built a pair of these for myself using Hammond transformers and GEC run the KT88 at top whack dissipation of 42Watt, I didn't think modern KT88 could/would handle that, so I experimented with KT120 and finished up with KT150 which are seriously under run.
Anyway back to the txs. It would be interesting to find out what the optx ratio is.
As it has several secondaries simplest way is to connect all in series, connect the two primaries together, then feed 10Vac across secondaries and measure across the primaries. The will give you the voltage ratio so the impedance ratio is that number squared then related to 16R or 8R whatever.
e.g. 10V in = 100V out = 10:1 voltage ratio therefore impedance ratio is 100:1. relate that to 8R = 800R primary impedance anode to anode.
I would hazard a guess that it is a5k or 10K a-a type.
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A very good modern valve rectifier is a 6D22S which although is a 6.3V heater runs exceptionally well off of 5V and is virtually bomb proof and even better dirt cheap! Snag is you need 2 for fullwave rectification but even so I think a pair will set you back about £10.00

John

Last edited by John Caswell; 8th Mar 2018 at 6:28 pm. Reason: Added info
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Old 8th Mar 2018, 6:31 pm   #16
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Default Re: Partridge Transformers

The power transformer would be handy for an old style velodyne servo amplifier using 807 type valves to drive the motor field windings.
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Old 8th Mar 2018, 8:44 pm   #17
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Default Re: Partridge Transformers

Remember you can get the dc ht down to less stratospheric levels (nearer to the voltages on the TX) by using choke input filtering. The output voltage will be more stable with a varying load, too.
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Old 8th Mar 2018, 10:44 pm   #18
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Default Re: Partridge Transformers

That's my bet too.

Partridge started using that C-core arrangement with the CFB style output transformers that come out in 1951 for Williamson amp application.
https://www.dalmura.com.au/static/Pa...datasheets.pdf
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Old 8th Mar 2018, 11:33 pm   #19
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Default Re: Partridge Transformers

With the choke input filter, the voltage will still go high if the load current drops to zero, so you need to rate things to handle the case of some valves being pulled out without there being any surprise sound effects.

David
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Old 9th Mar 2018, 7:36 am   #20
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Default Re: Partridge Transformers

"er no Andy, you'd theoretically get 630 or 700v, using the CT for 2 diode use." Yes it is tother Andy; bridge full wave rectified, no center tap used. Anyhoo, tfmr wasn't designed to be used that way, but it would power a pair of 813's.

It all depends what the OPT's Z ratio is really if one was to use these as a pair. Do you know their provenance resedwards1 and what do you intend to do with them?

Andy.
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