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[Sticky] Non destructive Tube Reactivation, Updated!

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(@irob2345)
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The back story to that label was that Astor was by this time owned by Philips, who were to use the new, expansive Astor plant in a few years to make colour TVs. So if you are upgrading the test plant, you'd install colour, right? That was the tenuous rationale for the "Colour Compatible" claim. And wouldn't it be nice if the mug buyer assumed that it was an Astor exclusive?!

 
Posted : 17/05/2025 9:27 am
(@nuvistor)
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@irob2345 Similar to the Pye adverts that they were supplying the transmitters for colour so Pye was the best choice for a receiver. I don’t think they supplied all the transmitters but that’s advertising.

I must say the the first dual standard Pye CTV’s did perform well, but so did some of the other makes.

 
Posted : 17/05/2025 9:45 am
(@irob2345)
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Yes AWA used that line in the early days of B&W TV here. And at one stage it was true.

 
Posted : 17/05/2025 11:00 am
(@nuvistor)
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Pye Brochure, scroll down for the transmitter info. The Pye CT70 and its Ekco stablemate were their first dual standard sets introduced in 1967, on the whole they were good CTV’s. Dual standard being 405 mono, 625 colour or mono depending on the programme.

https://www.radios-tv.co.uk/pye/

 
Posted : 17/05/2025 11:33 am
(@irob2345)
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Thanks for that Frank.

Interesting to see the switch to Philips chassis happened about the same time as it did here, and at least initially it was a step backwards.

Also interesting to see what we called the KL9 chassis, which Philips Clayton developed from the KT3 to replace the expensive to build and unreliable K12.

 
Posted : 18/05/2025 12:33 am
(@irob2345)
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Well I've just killed two CRTs in completely different ways!

First one was in a 12" Pye T25. A Philips A31-20W, 90 degree thin neck B7A base.

When I was given this set I was told the CRT was stuffed. Obviously when he tested it he didn't realise that it has a 12 volt heater. When I tested it I got 98% emission.

The PCB was covered in a carpet of dust, grass clippings, mouse poo and little pieces of what looked like shredded chocolate wrapper foil. So I dipped it in a solution of washing detergent and hosed it down.

While I was setting it up to catch the rays of the afternoon sun to dry, I bumped the tube socket board with the back of my hand. There was an ominous "tink" sound.

Sure enough, when it had dried and I fired it up, the tube was down to air. Bu@@er!

One down, one to go.

I have a completely knackered AWV CRT that I'd pulled from an AWA P5 portable. It had spent many years running with 14 volts on its heater due to a fault in the chassis and had been the test mule for my CRT tester. It was 110 degree but otherwise compatible, so I thought I'd try it in the Pye T25. Turn all the lights off, we might see something.

So I fitted it to the chassis and ran it up. 11 volt rail sitting on 13 volts due to a rotted lead on a zener. Replaced that, got the 11 volts back. With no signal, CRT cathode was on 45 volts, G1 on 43, G2 on 300. EHT normal. No light on the screen, after running for about 10 minutes.

CRT back on the tester. 12 volts on the heater, zero emission. Zip!

So I upped the heater to 15, still zip.

Up to 30, about 2% and slowly climbing. After about 5 minutes, it jumped to 95%. Back to 15, falls away rapidly. At 12 volts, zero again. Back to 30, goes to 2%. Let it run for an hour, no change.

2nd CRT down!

I'm not doing real well today!

Although I recall that, back in the B&W days, AWV tubes were the only brand that would not respond at all to reactivation attempts. Philips tubes would, but you had to be gentle with them. Thomas tubes would always respond and would generally give 6 months to a year of service. Small shop reguns were, as might be expected, variable. I don't think I ever needed to attempt a reactivation on an Anodeon tube, until recently that is.

 
Posted : 18/05/2025 4:36 am
(@nuvistor)
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@irob2345 We all have days like that, hopefully not quite as depressing.

 
Posted : 18/05/2025 3:50 pm
(@irob2345)
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Thanks. It was depressing!!

Maybe my experience might highlight for others the vulnerability of the 7 pin thin neck CRTs, where the exhaust tube is a close fit and passes through the middle of what is basically just a B7A valve socket with no protection.

During the chassis clean, in amongst the crud mat, I found a few pieces of broken neck glass that looked like they may have come from an earlier accident with a broken tube.

 
Posted : 19/05/2025 9:37 am
(@irob2345)
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Posted by: @irob2345

Here is one example, a 25" Thomas CRT in my HMV Y2:

The emission came up, as expected, to about 80% and stabilized. But then, after about 30 seconds to a minute, it suddenly jumped to 95%! This 95% reading remained when the heater was switched back to 6 volts.

Even better, after a 5 minute cooldown, switching the tester on again set to 6 volts, the emission rose rapidly to 95%. This from a tube that only got to 25% before and took 10 minutes to get there.

Plugging it back into the chassis, it looks almost as good as a new tube.

I'm wondering - does this parallel the way the cathodes were activated in new tubes?

I'll let the Y2 sit for a week, then power it up and see if the tube still looks good.

Well, it's been nearly 2 weeks and I just powered up the HMV Y2-D3

CRT first light after a week off   smudged camera lens

Look at that! What a pleasant surprise! It's come up like a new tube!

Sorry about the smudged lens and the bad angle, I was in a hurry to get the shot within seconds of the picture appearing. And frankly I didn't expect it would be so good!

 

 

 
Posted : 25/05/2025 9:37 am
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