UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio and TV Service Data

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > Specific Vintage Equipment > Vintage Test Gear and Workshop Equipment

Notices

Vintage Test Gear and Workshop Equipment For discussions about vintage test gear and workshop equipment such as coil winders.

Closed Thread
 
Thread Tools
Old 28th Jul 2018, 1:53 pm   #1
vintage_8bit
Heptode
 
Join Date: Feb 2013
Location: Rainham, Kent, UK.
Posts: 523
Default STC HT power supply.

Hello again. I have just obtained a Standard Telephones & Cables Ltd HT power supply. Model 94 LU 59. Has any one any information on this? I can't find a reference to it anywhere. It is actually 2 separate supplies in one. 0 to 250V and 0 to 500V.

It looks like its missing a cold cathode thyratron on the 0 to 500V side. I am hoping its the same as the one fitted on the 0 to 250V side which is a 4313C. Has any one any ideas on this. Its not been powered yet. I wondered if the thyratrons were used to energise a couple of relays on the chassis, but according to the valves data sheet they can also be used as a regulated voltage source.
I can't see any other reference source for any error amplifiers in the supply, so may be they are used for this? Please see attached some photos.
Attached Thumbnails
Click image for larger version

Name:	20180722_215011.jpg
Views:	272
Size:	58.2 KB
ID:	166679   Click image for larger version

Name:	20180727_222112.jpg
Views:	292
Size:	101.3 KB
ID:	166680   Click image for larger version

Name:	20180727_222253.jpg
Views:	263
Size:	118.2 KB
ID:	166681   Click image for larger version

Name:	20180722_215528.jpg
Views:	274
Size:	63.0 KB
ID:	166683  
vintage_8bit is offline  
Old 29th Jul 2018, 6:57 am   #2
Diabolical Artificer
Dekatron
 
Diabolical Artificer's Avatar
 
Join Date: Jul 2009
Location: Sleaford, Lincs. UK.
Posts: 7,639
Default Re: STC HT power supply.

Nice, though it needs a good blowout. What are those two black things with the pink wires attached, with a screw/knob on top. There are some very nice looking tfmr's in it, any idea of current capability?

Sorry, no idea re thyratron, according to this video -https://www.youtube.com/watch?v=WX74GoHuwHk&t=909s they are similar to SCR's.

Andy.
__________________
Curiosity hasn't killed this cat...so far.
Diabolical Artificer is offline  
Old 29th Jul 2018, 12:29 pm   #3
turretslug
Dekatron
 
turretslug's Avatar
 
Join Date: Nov 2011
Location: Surrey, UK.
Posts: 4,385
Default Re: STC HT power supply.

Intriguing one there- I wondered if it regulated by some means like PWM or phase angle, there's not a huge amount of anode area relative to the volume of iron, if you get my drift. There seems to be a fair bit of chokery, and some of the iron looks very vintage in style as do the valve envelopes. Having said that, some transformer makers didn't seem to change their house style greatly from the 'twenties to the 'seventies and probably more so for low-run stuff.

PS. Hope I'm not teaching to suck eggs, but if you post more details, it might be prudent to use subterfuge like phonetics or bingo calls for the more "interesting" valve types!
turretslug is offline  
Old 29th Jul 2018, 12:53 pm   #4
Refugee
Dekatron
 
Refugee's Avatar
 
Join Date: Apr 2012
Location: Worksop, Nottinghamshire, UK.
Posts: 5,549
Default Re: STC HT power supply.

I would guess that there should be some kind of cold cathode device that chops the power like a thyristor. There is a special looking two terminal wound component on the bottom left of the second and third photos that may well be a smoothing choke for such a device.
I have got a small one that was used to form a latching relay and indicator all in one by the looks of the circuit. It is going to be tricky getting it out without loosing one of the three caps. There is plenty of places on the web to see the data sheet for the GK40.
Attached Thumbnails
Click image for larger version

Name:	DSCF5323.jpg
Views:	126
Size:	42.2 KB
ID:	166721  
Refugee is online now  
Old 29th Jul 2018, 5:57 pm   #5
vintage_8bit
Heptode
 
Join Date: Feb 2013
Location: Rainham, Kent, UK.
Posts: 523
Default Re: STC HT power supply.

Thanks for your replies.
Andy. The 2 long black things with terminals I belive, are serries resistors to calibrate the volt meters. The one I measured was around 80k which roughly ties up with the 5mA meter. There's no clue to the current available, I expect the limit will mainly be down to the series regulator?
Turretslug. Dont worry about the big glass things, there staying in the power supply where they belong and no mention of the part numbers.

There are some good videos on the web showing the thyratrons glowing away.

Hopefully someone out there will have a circuit to save me some hard work. The missing thyratron I hope is the same as the other one which is readily available. I don't know how many different types there are that would fit the 4 pin base, hopefully none which would make it easy.

Colin
vintage_8bit is offline  
Old 29th Jul 2018, 10:21 pm   #6
WME_bill
Octode
 
Join Date: Oct 2007
Location: Exeter, Devon, UK.
Posts: 1,553
Default Re: STC HT power supply.

STC power supply.
I suspect the 4313 is acting as a reference voltage, as the maximum current rating is 20ma. The missing valve I suggest is a power thyratron, with phase control of when it fires to regulate the voltage.
Can you look at the output ratings of the unit. The 250v may be a negative, at low current, for bias, while the main output positive is to 500v at 500ma perhaps.
Please tell us more about what the front panel says.
A quick look at the wiring to the base socket of the missing valve will suggest the heater and other connections. What is heater voltage. Then tell us the type of base, probably large UX4.
Philips have published a lot upon industrial use of thyratrons for power switching and regulating. Try Industrial Electrical Handbook, Kretzmann 1959 for ideas. Nothing directly helpful.
Their industrial thyratrons include PL5557 and PL1607 families. The 2D21 / PL2D21 /EN91 on B7G base is the smallest and is not beefy enough for the current. Look at Frank Philipse Tube data.
STC valves will be similar to an American type and Philips tended to make similar.
The Ferranti GK40 you picture is a very low power thyratron, really used for driving counter tubes.
wme_bill
WME_bill is offline  
Old 29th Jul 2018, 10:49 pm   #7
vintage_8bit
Heptode
 
Join Date: Feb 2013
Location: Rainham, Kent, UK.
Posts: 523
Default Re: STC HT power supply.

I will have a look tomorrow now and report back on what I find. The base of the missing valve is the same as the 4313C as you rightly said a UX4. There is no clue on front panel as to the current available.
vintage_8bit is offline  
Old 30th Jul 2018, 10:57 pm   #8
vintage_8bit
Heptode
 
Join Date: Feb 2013
Location: Rainham, Kent, UK.
Posts: 523
Default Re: STC HT power supply.

Its quite difficult to check the wiring of the missing valve. There is no room between the base of the second UX4 socket, with the missing valve, and mains transformer. But it looks to me like both sides are very similar, just using different o/p (series regulator) valves. I think each side has its own rectyfier, error amp, reference, and output valve. The thyratron has only 2 connections and so I assume this can only be used as a reference. From what I can see the missing valve appears to be wired in a similar way. So not sure about phase control? There's no heater as the thyratron is a cold cathode device. So I'm still hoping the missing valve will be an identical thyratron. I will get round to powering it but a few suspect caps and r's to investigate first.
vintage_8bit is offline  
Old 31st Jul 2018, 9:19 pm   #9
turretslug
Dekatron
 
turretslug's Avatar
 
Join Date: Nov 2011
Location: Surrey, UK.
Posts: 4,385
Default Re: STC HT power supply.

Maybe not as high current/power as I'd assumed then- with linear regulation, the series regulator input would likely need to be 600V (preferably 650V?) under load for headroom with a 500V output. Even at a gentle 80mA output, that would imply 50W+ anode dissipation in the series valve when turned down to worst-case 0V output. All the same, it looks like a sturdy and well-made device and the dual-channel provision could be very handy. There have been times when I've been impressed by 250mA+ variable HT supplies but that's getting very large and hernia-risking. Not to mention wasteful.

Good luck with it.
turretslug is offline  
Old 31st Jul 2018, 11:30 pm   #10
vintage_8bit
Heptode
 
Join Date: Feb 2013
Location: Rainham, Kent, UK.
Posts: 523
Default Re: STC HT power supply.

I see "watt" you mean about the power. One of the chokes at the rear of the supply is huge. Maybe it is switching but I can't see how just now. My plan is with valves removed from the 0 to 450V side (not 500V as I incorrectly said), is to do a variac controlled power up on the 0 to 250V side and see where we are with it. I have only found one high value r so far. I'm in the middle of a radio job at the moment but can't resist a look at this supply. Will report back soon.
vintage_8bit is offline  
Old 1st Aug 2018, 6:09 am   #11
Diabolical Artificer
Dekatron
 
Diabolical Artificer's Avatar
 
Join Date: Jul 2009
Location: Sleaford, Lincs. UK.
Posts: 7,639
Default Re: STC HT power supply.

Just a thought, it wouldn't be a primitive switching supply would it? My big 500v 3A variable PSU uses two big SCR's, could yours be doing similarly with the thyratrons? But yours only uses one?? See here - http://jlandrigan.com/files/GRID%20C...ILE%20UNIT.pdf

Actually, thing about it, I have a STC booklet on VS valves that has a few PSU's in it, not sure if it has any PSU's with thyratrons, will look.

Andy,
__________________
Curiosity hasn't killed this cat...so far.
Diabolical Artificer is offline  
Old 1st Aug 2018, 10:59 pm   #12
vintage_8bit
Heptode
 
Join Date: Feb 2013
Location: Rainham, Kent, UK.
Posts: 523
Default Re: STC HT power supply.

I have now powered the 0 to 250v side. I'm not sure of its current capabilities but it can't supply 100ma. I will have a good look tomorrow now. Looking at the spec for the rectifier and o/p valve I don't think I can expect more than around 50mA? The 0 to 450v side though has quite a bit more
Capacity looking again at the valve specs. I found that the lowest it would adjust to is 100V going up to just over 250V The thyratron has 2 x metal semi circles when looking from top. Only one side is glowing? Never seen one lit before so not sure what to expect. Andy it might be interesting to see some circuits from that booklet. Colin.
vintage_8bit is offline  
Old 2nd Aug 2018, 11:19 pm   #13
vintage_8bit
Heptode
 
Join Date: Feb 2013
Location: Rainham, Kent, UK.
Posts: 523
Default Re: STC HT power supply.

I have now had each side powered individually. The 100 to 250V side stops regulating above 25 to 32ma. Around 5 to 6 watts. The 225 to 450v side with the larger O/P valve and rectifier could not manage any more than 70mA at the lower end (225v) which is around 16W. There is an overcurrent relay in the circuit which latches off if you demand to much.The regulation seems good up to its current limits on both sides.The same applies if you vary the mains supply.
The supply looks like it should be capable of more specially with the size of those transformers. Colin
vintage_8bit is offline  
Old 3rd Aug 2018, 6:51 am   #14
Diabolical Artificer
Dekatron
 
Diabolical Artificer's Avatar
 
Join Date: Jul 2009
Location: Sleaford, Lincs. UK.
Posts: 7,639
Default Re: STC HT power supply.

Interesting Colin, but tfmr size can be deceiving. I have a really nice big tfmr polygonal in shape, about 6" cubed, 80mA is all it can muster and for a lot of uses, useless. Are you happy with it's power OP, you could redesign it uses the bits.

BTW, what are the regulator valves?

I've looked for the booklet to no avail; will keep looking.

Andy.
__________________
Curiosity hasn't killed this cat...so far.
Diabolical Artificer is offline  
Old 3rd Aug 2018, 11:27 pm   #15
vintage_8bit
Heptode
 
Join Date: Feb 2013
Location: Rainham, Kent, UK.
Posts: 523
Default Re: STC HT power supply.

Re last para in post 3, I'll PM you the full line up. I have now another Thyratron so I will power up tomorrow with the full set of valves and take a few measurements.
vintage_8bit is offline  
Old 4th Aug 2018, 10:34 pm   #16
vintage_8bit
Heptode
 
Join Date: Feb 2013
Location: Rainham, Kent, UK.
Posts: 523
Default Re: STC HT power supply.

Now I have a complete set of valves the PSU seems to be working. I think for my purposes the limited output current will be sufficient. I did get it more to save it than to use it. But I'm sure it will be useful.
The output from the rectifier for the low HT side is 400V the hi HT side is 500V. The thyratron has 63V across it. It draws 500ma from the mains with no load on the outputs. Colin.

Last edited by vintage_8bit; 4th Aug 2018 at 10:36 pm. Reason: Extra info added.
vintage_8bit is offline  
Old 5th Aug 2018, 10:33 pm   #17
vintage_8bit
Heptode
 
Join Date: Feb 2013
Location: Rainham, Kent, UK.
Posts: 523
Default Re: STC HT power supply.

Just a footnote. I wondered how the overcurrent relays worked. Looking on the low HT side, I think it works like this. The relay has a 50 and 4000 ohm coil.
The 50 ohm coil with a 60 ohm resister in parrallel appears in the anode load of the output valve. When energised the 4000 ohm coil is used to latch relay.
vintage_8bit is offline  
Closed Thread

Thread Tools



All times are GMT +1. The time now is 4:38 pm.


All information and advice on this forum is subject to the WARNING AND DISCLAIMER located at https://www.vintage-radio.net/rules.html.
Failure to heed this warning may result in death or serious injury to yourself and/or others.


Powered by vBulletin®
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
Copyright ©2002 - 2023, Paul Stenning.