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Test Equipment Video Circuits 'Tripler Tester' V15

Vrat Founder Admin
Posts: 10842

This is a piece of test equipment I've been looking for, for a very long time. I had thought the chances were next to nil, to ever encounter one. I've not seen another in all the years I've been looking, and I only found one reference in a Television magazine from the 70s.

Normally I wouldn't touch anything coming out of the 'Video Circuits' stable, especially not their CRT tester/rejuvenator. However, the Tripler tester is something that has intrigued me and as far as I know, unlike CRT testers, nobody else had ventured into providing an instrument to test triplers.

The V15, if you've not already worked out from the thread title, is an EHT tripler tester. It tests drive absorption and final output on load. It produces pulses of around 800V pk-pk at 625-line frequency. There are five buttons, mains, 1-3 for DUT and the test button. Efficiency results are displayed on a meter, as a percentage. In fact, it tests not only triplers, but doublers and quadrupler's too, though I only know of one set that used a quadrupler.

  1. Single/Doubler
  2. Tripler
  3. Quadrupler


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I doubt many, if any, of these have survived, there's certainly nothing online. Thus, as far as I'm aware, this is an exclusive to VRAT. I will document as usual, with lots of photos, and put through its paces. The first thing to note is just how tiny it is. From the only photo I had from the TV mag, I assumed it was a large piece of kit. In fact, it only measures 8" wide x 3.5" at its uppermost height and 3.5" deep. Inside, there's not a lot to report, a TX, a switch bank, a couple of diodes, two electros, a few caps, resistors, pot to the meter and a single Brimar 12AU7 (ECC82).

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As you can see from the internals it looked to be in remarkable condition, throwing caution to the wind, powered it up, no dramatics. Now to give it something to test.

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Obviously no manual, so no operating instructions or circuit data. Connectivity although appearing to be simple, I'm a little uncertain of one of the connections. Red to EHT is self-explanatory, Blue to drive, I believe would be to the triplers input? Black to neutral, this is the one I'm unsure of, any thoughts? For example, here is a Granada Tripler of unknown state I'd like to test.

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Hmmmm not sure Yellow ? Grey is easy EHT, so connect that to Red, Green is Ground? The middle tag is Focus, The back tag ?

Topic starter Posted : 16/06/2022 2:46 pm
Lloyd, malcscott, Marconi_MPT4 and 2 people liked
Vrat Founder Admin
Posts: 10842

Looking at the picture on the back of the tripler, I connected the V15 blue drive connection to the back spare tag of the Granada tripler, which I believed to be input (drive). I then connected the V15 black neutral connection to the green wire on the Granada tripler which is GND. Finally, the V15 red EHT to the Granada triplers EHT.

I set the V15 to tripler, powered on, and pressed test, the meter read 100%. That indicates the line frequency pulses introduced into the tripler, produced 100% efficiency, thus the Granada tripler is good, and the V15 is working.

I think I kept a duff 8500, I'll see if I can find that now, to see what it produces.

D.U.T. Granada Tripler

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Topic starter Posted : 16/06/2022 4:12 pm
Noble V-Ratter Registered
Posts: 1631

Rare indeed, in fact that is the first I've ever seen other than pics in TV mag. I have a faulty tripler I kept from one my ITT FT110 sets, it generates EHT but has obvious tearing at high beam currents. I wonder if it would pick that up as a drop in efficiency on the meter? 

Re quadruplers, the only sets I know that used them were the Baird 700 series and later versions of the RBM dual standard hybrids. 

Posted : 16/06/2022 10:53 pm
Vrat Founder Admin
Posts: 10842
Posted by: @jayceebee

I have a faulty tripler I kept from one my ITT FT110 sets, it generates EHT but has obvious tearing at high beam currents. I wonder if it would pick that up as a drop in efficiency on the meter?

Hang on to that, we can test it next time you're over this way. I thought I'd kept a few of my failed ones, but it looks like I only kept one, and that's de-potted with parts removed, ready for rebuilding.

Topic starter Posted : 16/06/2022 11:10 pm
Noble V-Ratter Registered
Posts: 1493

Nice bit of kit. Only ever seen one before. Cap dated April 1972.

Posted : 17/06/2022 9:54 am
Trusted V-Ratter Registered
Posts: 166

At a glance it looks as if the mains is voltage doubled for the HT. At least the case is earthed!

Posted : 17/06/2022 10:21 am