Dukes & Briggs P5B2 Power Supply

[Colin]

I came across this rather small, but useful looking PSU and was wondering if anyone had any information or documentation on it.

Better still, does anyone actually have one that they would be willing to send me some detailed pics of as I'd quite like to build a similar unit.

Thanks
Colin

[Radio_Dave]

Hi Colin,

Yes I have one of these and so does (or did) forum moderator Chris_C. Between us we drew a circuit diagram because we both had problems with too much voltage! Mine was throwing out over 600V ... One day I'll sort it out!

Anyhow here's the circuit diagram that Chris finally came up with.

Regard
David

[Colin]

This forum never ceases to amaze ... That was quick.

Thanks Dave the curcuit is really useful. Do you happen to know what the voltage at the HT secondary outputs of the mains TX is? Also, is the lower of the two 50k pots used to set 0v?

You don't happen to have any pictures handy do you?

Thanks again
Colin

[Radio_Dave]

Hi Colin,

Unfortunately it's been in the garage for about a year and it'll need a good couple of weeks in the airing cupboard before I dare take any voltage measurements!

I've been looking at the circuit, that I posted, and I have to say that I don't understand it and I'd also like to mention that I'm making no claims that it's been drawn correctly

I do remember that the smoothing electrolytics were rated at 500V and I had to change them because the voltage to them was around 560V Whether this was due to the 8 metal rectifiers complaining or a fault somewhere else, I'm not sure .

I'm also not sure if that lower pot sets the 0V or calibrates the variable 0-300V

Anyhow, I think I can be more helpfull with pictures... what do you need

David

[Colin]

Dave & Chris,

Thanks for being so helpful. I was hoping to get hold of one of these because they look really handy. It's the small size that I like as most High Voltage regulated PSU's are much bigger.

I just missed out on the one in the picture (forgot about the auction ending and was outbid), and as I've never seen another I thought I'd have a pop at building a 'replica'.

So, from a pictures point of view, anything that'll help me fabricate one. Chassis top and bottom showing component locations, etc. and a good picture of the facia would be useful too. Oh, and some measurements would come in handy - just the basic L x W x H.

The voltages would be nice too, but not essential I suppose as I could work backwards from the output voltages.

Thanks again, your help is really appreciated.

Regards
Colin

[Radio_Dave]

Hi Colin,

It measures around 10.5" x 8.25" x 4.25" .

I've taken several picture of it, please PM me you email address and I'll send them to you.

Regards
David

[mark_in_manc]

Thanks to Mike T for re-opening this old thread. I just found one of these units in a bin at work, and this thread seems to be the only source of information on the whole internet! So, as it is a useful thing, and a product of a little-known outfit kind-of local to where I live (they also made decade resistance boxes - I have one somewhere), I thought this might be a thread worth re-opening. I'll provide a pic in a bit, and perhaps some pics of the inside, and I'll have a go with the circuit diagram helpfully provided above and see if mine is the same. And if some clever person wants to explain how it works to me using that diagram, that will help too!

(I've got as far as measuring the o/p on mine and it appears to work. That's a great start.)

[lesmw0sec]

I'd be inclined to add a fuse in the HT feed from the transformer. A bit of flash-over from the series reg. can do wonders. I speak from experience with a similar set I built in the late 50's using an 807.

[PJL]

Very similar to the HT regulator in the Mullard Valve Tester but I guess there are not too many ways to design a series regulator.

Not sure the drawing is correct as the EF86 cathode seems to be taken to an unregulated -ve supply. The Mullard design takes it to 0V but this unit needs to be able to run the EF86 anode at -ve voltages to achieve the low output voltages. If the cathode is connected to the regulated -150V then then that raises concerns that the EF86 anode voltage can far exceed the 250V specification.

[mark_in_manc]

I have started tracing my way through the (very useful!) circuit diagram, but even on something this simple it is taking me a while. So far, on my unit the first discrepancy is that the 15k resistor shown between the regulator valve GD150M cathode and the -150v o/p, is instead in the line from said cathode to the output adjusting potentiometer - the GD150M cathode is directly connected to the -150v o/p. I expect more odds and ends will come to light.

Perhaps it would be useful to add that the 50k pot in the negative part of the circuit, whose wiper goes to the EF86 cathode, is a 'normal' pot with a locked-off shank, used as a trim pot. I imagine it is set to get the output to more or less align with the scale printed on the front panel - on mine the wiper sits at -84v, so about half way through its travel. The other pot is the one connected to the knob on the front panel. When this one is rotated fully anti-clockwise, the o/p is at -12v, only rising to 0v somewhere around the start of the dial markings some 45 deg further clockwise. I guess drifting resistors will be why the scale alignment is a bit off all through the range.

From the date codes on the valves in mine, it appears to date from 1967.

[Electrical]

I have just noticed this thread and I have realised that this PSU is similar to the Briggs PSU I have, the exception being that the PSU I have has a variable 0 to 15 volt negative supply.
Please see attached PDF copy of my hand drawn diagram and some photo's of the unit. It looks like I must have completely rebuilt it as it is full of new resistors, capacitors and rectifiers.
Regards Stan.

[mark_in_manc]

Thanks for adding that Stan - it looks a lot like mine, and a lot like the one up the thread in post #2, with the correction I noticed in post #10.

The 33k resistor had me scratching my head. I have not come across body-tip-spot resistors in the wild before, so the one which was just 'all orange' had me wondering until the penny dropped

[David G4EBT]

I've got one of these.

I bought it about 20 years ago - a lucky find from a car boot sale for a fiver.

As the logo on the front panel 'Regulated Power Supply B' looks like the outline of a power transistor such s the 2N3055, I mistakenly assumed it was solid state. When I took it out of its case, I was surprised to discover that it had three valves, one of which was a 150V stabiliser. As it has four finned selenium rectifiers and a selenium contact cooled rectifier, along with three carbon rod 'body tip dot' resistors, a wire-wound resistor and a couple of tubular 1 Watt ones, I guess it would date from the early 1960's. The 50k wire-wound chassis-mounted variable resistor seen on the underside of the chassis isn't user externally adjustable - it's pre-set.

All of the components appear to be original, but unfortunately, there are no date codes on any of the capacitors to enable me to date it. I've not used it often, but have just checked its accuracy at the 18 Voltage steps from 10V to 300V and it's spot on.

The construction is robust and to a high standard.

Presumably it was meant for use when servicing radio equipment, but forgive my ignorance, why the -150V? output sockets?

I didn't have a circuit, so thanks to Radio Dave and to Stan.

I've been able to find out little about this enigmatic company.

There's a mention of it in Grace's Guide here:

https://www.gracesguide.co.uk/Dukes_...Engineering_Co

The company also has a 'CAGE' Code. 'K' in the code number means 'Item meets government specifications'.

CAGE Code: Stands for “Commercial and Government Entity”. It is a unique five-character alphanumeric identifier that is required for a company to do business with the government. International use is performed through the NATO Codification System, or NCS, and those are NCAGE codes.

K7483 CAGE code - DUKES & BRIGGS ENGINEERING CO LTD

Read more at: https://www.cage-codes.com/cage-code...neering-co-ltd

A few pics attached.

Hope that's of interest.

[mark_in_manc]

That's the same as mine, David - thanks for posting. I dated mine based on the date codes on the valves - I doubt they have been changed - perhaps this would work for you too, given the absence of dates on anything else. I wonder whether 'Urmston' meant the works were in the small SW-Manc suburb of that name, or whether it was an attempt at an upmarket address for premises in Trafford Park!

Edit - while we're collecting info about this company in one place, here's a brief biog of Mr Briggs himself which I stumbled over.

https://prabook.com/web/philip_harold.briggs/642959

[David G4EBT]

Originally Posted by mark_in_manc

Edit - while we're collecting info about this company in one place, here's a brief biog of Mr Briggs himself which I stumbled over.

https://prabook.com/web/philip_harold.briggs/642959

That was well spotted Mark!

What a gifted and industrious man he was: BSc, MSc, PhD, LLB, and what a fulfilling life he had on so many fronts, including serving in the REME in North Africa from 1942 (age 21) until 1947, then from '47 to '51 back with Ferranti, where he was Chief Design Engineer, Domestic Products, which I guess was mainly radios?

Presumably, as joint managing director of Dukes & Briggs Engineering Ltd. and Flow Control Ltd., Trafford Park, Manchester, from 1951-1953, along with 'Mr Dukes', (as the other joint managing director?), they were the co-founders of the company? He then left and went into academia, so whether the company ceased to exist or continued in business after he left, I guess we'll never know. However, Mark's valve date codes suggest they they were in business in the mid 1960s.

I don't ever recall seeing the power supply advertised in any magazines such as PW or WW.

Maybe they were marketed to colleges and universities rather than the wider general public?

Back to the Power Supply, mine has the 400mA re-settable trip on the transformer primary, but doesn't have the 0-15V (adjustable) addition as Stan's version does. I wonder that the purpose of that was? EG, for equipment with different heater voltages: 1.4, 2, 7.5V etc, or grid bias? Likewise, why the -150V stabilised?

Pic shows the re-settable trip.

[mark_in_manc]

Seems to have done a lot, doesn't he! I had assumed that a -ve fixed v_ref was needed to index the bias conditions to something, and since it was there they decided to make it available to lab users from which to derive a grid bias supply for their valve experiments. Stan's one takes that a step further by providing a pot with a useful (0 to -15v) range, internal to the device.

As it's unlikely to ever feature in a thread of its own, here is the resistance box I have which was made by the same people.