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Non destructive Tube Reactivation, Updated!

Pre War 240/405, Post War 405 Line, B&W Dual Standard, Colour Dual Standard, B&W S/S 625, Colour S/S 625 line, Hybrids. Standards converters & modulators, video recorders.
 
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Re: Non destructive Tube Reactivation, Updated!

Post by rob t » Mon Dec 08, 2014 6:52 pm

hi Rebel Rafter.
do you know that there is a low value resistor in series with the crt heater on this set, you could try a lower value or just short it out.
Rob T

 
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Re: Non destructive Tube Reactivation, Updated!

Post by Red to black » Mon Dec 08, 2014 7:33 pm

Hi RR, as far as I can recall I never had much (if any) success boosting the A56/66 540X CRTs, they almost always fell flat shortly afterwards, sometimes in minutes :bbd , at best over a few hours/days.

 
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Re: Non destructive Tube Reactivation, Updated!

Post by Rebel Rafter » Mon Dec 08, 2014 8:05 pm

Hi folks, thanks for your replies so quickly. Yes I know about the series resistor in the heater supply line, R729. For some reason thorn didn't seem to be able to make up their minds about the value, anywhere between 1R8 and 2R7, with 2R2 sometimes being fitted, with an extra 0R22 on the tube base panel if an S4 tube was fitted. My chassis is the 1560 series, that's the one with the plastic frame and revised layout and field timebase. I have the manuals for the three versions of the main chassis and for the remote control and teletext systems in the stereo versions, as well as the diagrams for the stereo sound system. The RGB input is easy to fit, and that works, but there is no sync., which I think is hardly surprising when the video preamp, according to the article in the magazine has a gain of 2.5, when apparently it should be three. My manual says that the output from TDA2540 is 3volts peak to peak and the input to the scart socket has to be the industry standard 1volt pk.-pk., so I think it would be interesting to see what kind of circuit thorn designed for the same purpose. Thanks, RR.

 
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Re: Non destructive Tube Reactivation, Updated!

Post by sideband » Tue Dec 09, 2014 12:49 am

I've moved the latest posts here with a new topic heading seeing as they were nothing to do with tube reactivation!

 
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Re: Non destructive Tube Reactivation, Updated!

Post by peter scott » Wed Sep 07, 2016 2:45 pm

I was chatting to an ex-tv-repair man recently and he said that he had had a lot of success with reactivation but he stressed that it was important to place the CRT with the screen uppermost and neck pointing vertically downwards. Aparently this reduces sparking and also ensures that the cathode surface (which becomes molten) is spread nicely rather than off to one side. He had been using a B&K 467.

Peter

 
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Re: Non destructive Tube Reactivation, Updated!

Post by rob t » Wed Sep 07, 2016 5:15 pm

never heard of that before. only ever reactivated tubes in situe
testing some times done with tube face down because not installed in set
Rob T

 
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Re: Non destructive Tube Reactivation, Updated!

Post by peter scott » Wed Sep 07, 2016 6:07 pm

Here's his advice:

I forgot to mention an important detail about reactivating CRT's, you'll remember I said do it with the screen uppermost, what I also should have added, but forgot, was don't take the crt out of cabinet, leave it all as it is, just get two chairs side by side, spread them apart so that they are a few inches narrower than than width of the cabinet, and then rest the TV between the chairs with the base of crt facing the floor.
Couple up your tester( on the floor next to you) and check it all out.
I've done it hundreds of times, providing you take care, the chairs must be the same, and be firm, its a doddle. Should the TV slip then all will be ruined, your reputation as well, so no "that will do" its got to be 100% safe, watch out for flimsy plastic cabinets, they can be nasty, as I said, only 100% is good enough, be warned.

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