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Burning out an intermittant heater-cathode short in a CRT

I can't seem to find one. But I think it is indeed just a spare pin, especially because the neck board also connects them together.

What I meant was, that most repair guys aren't really interested in delivering a perfect monitor. They just want their paycheck and be done with it. I have experience with the repair service in question (the only company in The Netherlands that is authorized by Eizo), and I know what shabby calibration they can do. On the other hand, I can't do any at all (the correct way), so for that matter...

BTW, I found something on impregnated cathodes, which is what Sony Trinitron tubes use:

are

I guess this depositing is what's been happenning. Can someone tell me if the cap-discharge method, or professional rejuvenation, is perhaps particularly dangerous? (just trying to rule out damaging this monitor...)

Reply to
Wiebe Cazemier
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I meant, for this type of metal build-up?

Later on in the repair FAQ, it says this:

So, I guess with impregnated cathodes I run less risk of burning them out.

Reply to
Wiebe Cazemier

I'm going to build my own K-G1 zapper. I thought I'd put my idea up for comments here.

- Get 325Vdc by rectifying 230Vac mains (provided by 1:1 isolation tranny).

- Charge 2.2 uF up to that DC potential.

- Discharge through two 400 Ohm resistors in series (to limit current to 400 mA. The repair FAQ has a comment in it, saying that if you need more than 400 mA, the cathode is usually toast. Two resistors because one resistor has a max voltage of 250V. I found that Sencore's CRT regenerators use a current limiting resistor [1], but I don't know which value (or which value cap).

- Increase value of cap step by step should the short not go away.

[1] Also says that it turns the heater off before attempting the discharge, to protect the cathode. Is this really a problem, seeing as how the short does not register without the heater on in my case?

Comments about resistor and cap value are most particularly requested.

Thanks in advance, as always :)

[1]
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Reply to
Wiebe Cazemier

I've had mixed results with a stun-gun. Lotsa volts, but not enough current to break much. I just arc'd it between all combinations of pins until I got bored with the light show. No idea where the short was, but it worked afterwards. YMMV.

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Reply to
mike

Haha, I like that :). Using any kind of tesla coil would do about the same, I guess. I'm working on constructing a device which gives me a current limited jolt at 325V (described in another post in this thread). Let's see how that works out. 350V is the amount a Sencore rejuvenator uses, so that seems pretty safe to me.

But about your stungun method: if it worked afterwards, what are the mixed results you speak of?

BTW, I've always wondered, what does an arc look like in a vacuum. In air, the air ionizes, giving the thunderbolt like arc. But in a vacuum, this can't happen. So, will the arcing be invisible when the short has been completely blown out?

Reply to
Wiebe Cazemier

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