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Granada Television Brochure, 1970s
Long Gone UK TV Shops
Memories of a Derwent Field Service Engineer
PYE Australia Circa 1971
Radios-TV VRAT
Fabulous Fablon
Thorn TX10 Chassis
Crusty-TV Museum, Analogue TV Network
Philips N1500 Warning!
Rumbelows
Thorn EMI Advertising
Thorn’s Guide to Servicing a VCR
Ferguson 3V24 De-Robed
Want to tell us a story?
Video Circuits V15 – Tripler Tester
Thorn Chassis Guide
Remove Teletext Lines & VCR Problems
Ceefax (Teletext)
Suggestions
Website Refresh
Colour TV Brochures
1970s Lounge Recreation
CrustyTV Vintage Television Museum
Linda Lovelace Experience
Humbars on a Sony KV2702
1972 Ultra 6713
D|E|R Service “The Best”
The one that got away
Technical information
The Line Output Stage
The map
Tales of a newly qualified young engineer.
Tales of a Radio Rentals Van Boy
Sanyo SMD
Disastrous Company Rebranding
1969 Philips G22K511
Memories Of The TV Trade
Crazy house
Dirty TV screens
Dual Standard and Single Standard CTV’s
Radios-TV on YouTube
The Winter of 62/63
A domestic audio installation
1979 Ferguson Videostar Deluxe 3V16
Music centre modifications
Unusual record player modification
B&K 467 Adapters
Mishaps In The Trade
1971 Beovision 3200
1971 Bush CTV1120
A.P.T valve stabilised PSU
Hi all,
My next project will be this power supply I have just bought for £80 on ebay. (It was £100 originally). Bearing in mind that a good Mullard GZ34 rectifier can fetch this figure alone, I thought it was a reasonable price with free postage too.
It caught my interest as it is a valve stabilised PSU and will be useful for me playing with valve amplifiers etc.
Judging that it seems to have three EL86 series pass output valves, I am guessing it is able to provide a likely output of 250-300vdc upto 150mA. There is also an ECC83, 81 and an 85A2 voltage stabiliser.
It was made by a company called A.P.T in Surrey and I would guess it dates from the mid 60's.
Here are the vendor's photo's for now....
To understand the black art of electronics is to understand witchcraft. Andrew.
Very nice Andrew and very useful, look forward to it on your bench and the reports.
I have a much more modern affair, weighs an absolute tonne. A Claude Lyon Voltage stabiliser. They sound grand but its basically a motorised variac that maintains a steady state voltage that the user sets. I bought mine to supply my valve tester with the steady state supply. No point trying to test valves with a fluctuating mains input the suppliers deliver us, skews all the readings. Hardly gets used now as I hardly ever test valves anymore.
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Marc said
Good grief ! Are GZ34's really fetching that sort of moneyMarc.
Yes and have been for some years now. My first valve tester had its one stolen when I bought it. I had to slap two silicons as the glass was waayyy too expensive.
CrustyTV Television Shop: Take a virtual tour
Crusty's TV/VCR Collection: View my collection
Crustys Youtube Channel: My stuff
Crusty's 70s Lounge: Take a peek
A Mullard or Philips GZ34 can be rather pricey to say the least, especially if it has a metal band around the base. For some reason, these must be so much better. I'd love to know why
Have a gander on ebay, you'll soon see what I mean about the prices.
To understand the black art of electronics is to understand witchcraft. Andrew.
Marc said
Correct, and they are just as good except for perhaps the most demanding of applications.
As for the PSU, I will try and find some data on it, but until I can see the model number there is little chance. Even knowing the model anyway, it could be difficult.
To understand the black art of electronics is to understand witchcraft. Andrew.
Chris said
Very nice Andrew and very useful, look forward to it on your bench and the reports.
Speaking of benches, I have just bought a used one locally and am collecting it Friday. It is 80cm deep and will be better for TV set's than the 60cm I have at the moment. (I'll put some pic's later in my "new workshop" thread.)
To understand the black art of electronics is to understand witchcraft. Andrew.
https://www.radiomuseum.org/dsp_hersteller_detail.cfm?company_id=15204
Just some company information, no circuit.
There are some valve regulator designs in WW or the Practical Wirelss/TV, probably very similar. Worth a search.
Frank
Thanks Frank,
Reading the info could mean that the PSU was made just prior to 1960, on account of the company moving to Reading in that year and the PSU label stating "Byfleet, Surrey".
That's a bit confusing.... Am I reading in Reading, or Reading in reading ?
To understand the black art of electronics is to understand witchcraft. Andrew.
Hi all, the PSU arrived safely and well packed today and the model is IVC 250. (Nothing on Google about it that I can find).
Once I have some bench time, I'll have a look at it 🙂
To understand the black art of electronics is to understand witchcraft. Andrew.
As usual, I couldn't wait, and had more than a quick peek.
The transformer is ok, the main smoothing caps are 4x 100uf 450v and are reading nicely between 99 and 104 uf. They are being re-formed at the moment. I applied mains, all valves in place except the GZ34 rectifier which is fine fortunately, and checked the AC voltages. All ok heater voltage wise and the HT secondary is approximately 320-0-320 vrms. So good, so far. 🙂
To understand the black art of electronics is to understand witchcraft. Andrew.
This is just going to work, especially with the slow warm up you are giving it.
Frank
Posted by: PYE625As usual, I couldn't wait, and had more than a quick peek.
I would expect nothing less from you 😉
Marc.
Marc
BVWS member
RSGB call sign 2E0VTN
This evening I have been sketching out the circuit. One odd thing for me is that two 100uf 450v capacitors are wired in series for main smoothing and again on the set output voltage. From what I can see, HT is not going to be much greater than 375 volts at most, so what the point of this is, I have no idea.
Here is my attempt at circuit drawing.... On paper it looked ok, but now on here it's hard to read so I will re-draw it sometime. 🙂
To understand the black art of electronics is to understand witchcraft. Andrew.
Some pics of the capacitors being reformed en-mass and of the unit itself.
To understand the black art of electronics is to understand witchcraft. Andrew.
Presume they have used two to reduce the amount of heat in each on for long term reliability. 60uf is the max reservoir cap for a GZ34 so that will be the reason for them using 100uf.
Its also possible that in the design stage that found some anomaly and decided this was an easy way around it.
It not a consumer item so perhaps they built it a bit better.
All guess work as usual on my part.
Frank
Thanks Frank, whatever the reason is I won't be changing the design. There are some large green wire-wound resistors marked APT and have custom values eg. 10.4 k, 17k, 8.75k and a 5.63k. They are marked as 1 %. Fortunately, these are ok. There are some bog standard carbon resistors too, and the values are out of spec on some so they will be replaced....namely the 150k's across the 100uf capacitors.
The electrolytics have reformed very well and the unit is now working, but one or two resistors and paper capacitors will need to be replaced. (I have replaced the valves that were broken, 1x EL86 and an ECC83).
PS....I have spotted at least one error in my circuit above, so please don't treat it as gospel.
To understand the black art of electronics is to understand witchcraft. Andrew.
In re-forming the electrolytic capacitors pictured above, I cheated and split off the HT through four individual 27k resistors for each capacitor. This way, I was able to do them all at once. I achieved a HT source of 380vdc in a slightly naughty way, I used the 320v output from my capacitor reformer in series with an additional isolated 60v psu. The reason for this was to get nearer to the 450v rating of the capacitors. Whether I really needed to do this, I don't know, would 320v have been sufficient to properly reform 450v capacitors?
To understand the black art of electronics is to understand witchcraft. Andrew.
Who knows, at the price of GZ34 I think you need to do everything to protect the one you have.
I didn’t realise they were selling for that money.
Frank
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