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Old 2nd Jan 2014, 11:17 pm   #1
Wendymott
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Default Variable HT Voltage Regulator

Hi Peeps. Has anyone got a schematic for a HT adjustable Voltage regulated PSU. Typical variation 200 - 300V DC say 100M/a.... I have 2x 5B255M Valves, but do NOT want to use them in Shunt Mode.... I hate wasting power.
I did have such info years ago, but time has passed and this info has been lost.
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Maybe power fets could be used............
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Old 3rd Jan 2014, 12:02 am   #2
GrimJosef
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Default Re: Variable HT Voltage Regulator

Have you considered modifying the circuit of the Sussex valve tester https://www.vintage-radio.net/forum/...ad.php?t=48853 ?

Cheers,

GJ
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Old 3rd Jan 2014, 10:20 am   #3
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Default Re: Variable HT Voltage Regulator

Hi Wendy, have a look for threads on the Farnell HV power supply in the Forum. That uses 2, EL34's as the series pass elements and the circuit is shown in the thread. I built a modified version foe a friend using 807's. Control electronics are transistor.
Power loss is minimised by using a transformer that has tappings every 50v or so. I wound my own and can let you have details if you wish.
These PSU's do appear fairly often for sale on e-bay.

Ed
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Old 3rd Jan 2014, 10:54 am   #4
Pamphonica
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Default Re: Variable HT Voltage Regulator

Hi Wendy, the Farnell PSU manual with circuit is here.
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Old 3rd Jan 2014, 11:55 am   #5
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Default Re: Variable HT Voltage Regulator

Hi Wendy

This Heathkit circuit may be useful.
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Old 4th Jan 2014, 12:22 pm   #6
Wendymott
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Default Re: Variable HT Voltage Regulator

Thanks to you all for replying...................As it happens I have found one using a H V Fet.........Arghhhhhhhh you are all saying......but its a practical solution and that's what I need............Again thanks to all that replied......
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Old 4th Jan 2014, 1:01 pm   #7
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Default Re: Variable HT Voltage Regulator

Hi Wendy, make sure it has a "crowbar circuit" on it.
Fet's tend to fail s/c and can damage the equip under test. Valve series pass elements will also fail s/c but general have a higher s/c impedance and lower risk of damage to the EUT.

Ed
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Old 4th Jan 2014, 1:30 pm   #8
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Default Re: Variable HT Voltage Regulator

This thread contains the circuit of the Solartron SRS 153.1 power supply.

Rob.
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Old 4th Jan 2014, 1:37 pm   #9
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Default Re: Variable HT Voltage Regulator

Power MOSFETS will allow you to run with less overhead voltage, and less waste energy. Most of the good series-pass valves used in regulated HV PSUs have been latched onto by the audiophiliacs so the prices have gone silly.

I'll second what Ed's said about a crowbar. Based on the principle that what a PSU is powering is worth a good deal less than the cost of the PSU, but can easily be destroyed by a PSU fault, I've always been amazed at how PSUs have always been the poor relative. Make sure that if the crowbar triggers it pops a fuse or opens a breaker without doing any damage.

One parameter everyone forgets with regulated PSUs is bandwidth. What are you powering? Does the current fluctuate (EG RF power amp running SSB or CW, or AM for that matter) You want to make sure the PSU responds nicely. I've seen some which bits of speech can excite into wild overshoots between zero and the full unreg voltage...

Just back from the Christmas break. Is the poly trying to take over Huddersfield?

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Old 5th Jan 2014, 1:26 pm   #10
Wendymott
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Default Re: Variable HT Voltage Regulator

Hi David and Rob and Ed. The HT psu is for general Bench use, rather like my LT PSU...Thanks for all the useful info...the circuit I am going to use has a 22R series resistor as a current sensor to limit at 100m/A....Occasionally.. a HT Supply is useful... I used to have many such items.. "in the past"..now I am coming back to my youth..I am getting "valve-itus".... thus the renovation of Eddystone receivers and such.
David, the University keeps "re inventing" its self....The Tech has moved to a brand new building and the council is erecting a new sports centre on the Ring road...
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Old 2nd Feb 2014, 9:27 pm   #11
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Default Re: Variable HT Voltage Regulator

I followed glowinganodes link to the Solartron HV PSU, are Solartron and Pye connected in any way? Just aquired a Pye 8440 PSU, 500V (in four ranges) at 250mA, uses five EL34s. Not certain I am brave enough to use it, even turn it on, 500V bites. But a circuit or other info is always interesting.
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Old 3rd Feb 2014, 12:01 am   #12
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Default Re: Variable HT Voltage Regulator

Quote:
Originally Posted by woodchips View Post
...... are Solartron and Pye connected in any way?
Unlikely, not as far as I know.
Solartron (Power Supplies) were in Thames Ditton, Pye I assume were around Cambridge somewhere. Both dealing with very different market sectors.
The choice of series regulator valves in kit of this vintage was fairly limited, EL34, 5B/254M / 807, 12E1 and 6080 seemingly most common.
Sounds a nice unit you have there, and would love to see some pictures of it.

Cheers, Rob.
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Old 12th Feb 2014, 5:21 pm   #13
woodchips
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Default Re: Variable HT Voltage Regulator

Rob, some pictures of the Pye PSU.

Does 0-500V @250mA in four ranges, 0 to -250V @ 1mA, -250V @ 30mA and 6.3V CT @ 5A. Valve line up is 5R4GY x2, 85A2, CV492/12AX7 x2, EL81 x2, ECC81, EL34 x5, DSL16 and EF91 x2. All Mullard apart from Brimar 5R4 and STC DSL16. Weight about 30-35kg, just lift it.
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Old 13th Feb 2014, 9:31 pm   #14
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Default Re: Variable HT Voltage Regulator

Thank you for taking the trouble, a fine selection of ironmongery there!

Cheers,
Rob.
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