Strange part connected to flyback of Atari SC1224

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sandord
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Re: Strange part connected to flyback of Atari SC1224

Post by sandord » Mon Jan 07, 2019 12:20 pm

exxos wrote:
Mon Jan 07, 2019 11:29 am
Dielectric = insulation..

That is, it would take for example over 7,500 volts for it to arc though the insulation to whatever its next to ( such as anything metal etc). So you really want that figure as high as possible.

I don't know the voltages on those lopt's though, they can be as high as 30,000 volts, though generally around 18-22KV I think.. Don't exactly remember.

EDIT:
Though as it has a trippler, the lopt output voltage isn't likely going to be higher than 10,000 volts. So 7,500V (7.5KV) is probably OK between the lopt and tripler..

Though I don't really recommend splicing HV cables..
Thanks, that opens up some more possibilities.

I don't really want to do splicing but I'm afraid I have no choice, no way I'm going to find a new LOPT+tripler set that's pre-wired like the original.

By the way, triplers don't have the fine wiring that LOPTs do, don't they? I suspect that may mean that triplers don't wear as fast as LOPTs do... At least so I hope. That would justify not replacing the tripler a bit more.

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Re: Strange part connected to flyback of Atari SC1224

Post by exxos » Mon Jan 07, 2019 12:46 pm

sandord wrote:
Mon Jan 07, 2019 12:20 pm
By the way, triplers don't have the fine wiring that LOPTs do, don't they? I suspect that may mean that triplers don't wear as fast as LOPTs do... At least so I hope. That would justify not replacing the tripler a bit more.
They are just a few diodes and capacitors..

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Re: Strange part connected to flyback of Atari SC1224

Post by PaulJ » Mon Jan 07, 2019 2:12 pm

I wouldn't cut any of the high voltage wiring, everything should be connectorized or it all comes as one piece. When your dealing with high voltage and you solder connections anything that comes to a point is a spot where arc's can occur.`

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Re: Strange part connected to flyback of Atari SC1224

Post by sandord » Wed Jun 24, 2020 5:16 pm

Out of fear of electrocution I kept delaying this project. But suddenly a question popped up: what if the replacement LOPT (which I already have in my possession) has a built-in tripler? I read that some LOPTs do, so why not in this case? Imagine bolting a tripler to the replacement LOPT and think of the resulting voltage... The explosion would've been HUGE :o

I'm SO glad I didn't try that!

Then I went looking for more evidence and found this: https://www.electro-tech-online.com/thr ... er.156254/

Apparently, the 'tripler' is not a tripler but a simple RC, bleeder resistor+capacitor that "helps regulate the high voltage supply by placing a minimum load on it."

So, as they say in that post, it shouldn't make much difference.

Well, I couldn't have hoped for a better outcome because it seems I won't have to do anything about it, just install the new LOPT :D

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Re: Strange part connected to flyback of Atari SC1224

Post by sandord » Wed Jun 24, 2020 5:22 pm

This quote from the post nicely sums it up (at least I hope so):
Performance wise the only differences if those components are not inside the transformer are:

1 - the CRT will stayed charged up - this is extremely common anyway.

2 - without the capacitor the picture may experience more 'blooming' (picture size varying with brightness).

Most CRT sets didn't include either of those two components, relying on the CRT capacitance (between aquadag and final anode) to provide enough.

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Re: Strange part connected to flyback of Atari SC1224

Post by exxos » Wed Jun 24, 2020 5:52 pm

Not sure I've seen that before , though I'm not a monitor expert.. Ones I've seen are just from the lopt to CRT. Nothing else there. Though these were internal doublers in them. I half recall seeing ones with a external triplers longgg ago. Even so, I don't think you can assume the lopt pinouts are the same, or what voltage they output.
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Re: Strange part connected to flyback of Atari SC1224

Post by sandord » Mon Jun 29, 2020 12:54 pm

sandord wrote:
Sun Jan 06, 2019 8:36 pm
Okay, so the manual actually does mention the tripler as an H.R.T. but no specs are listed.
I just saw that the parts list in the service manual actually lists it as H.D.T. under Coil & Trans.
Maybe that rings a bell for somebody?

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Re: Strange part connected to flyback of Atari SC1224

Post by Tomswork » Mon Jun 29, 2020 3:22 pm

I seem to remember that Phillips used a similar part in there tv sets for instant on. These are very reliable parts. I would start at the beginning if you have a signal generator.

Tom

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Re: Strange part connected to flyback of Atari SC1224

Post by sandord » Mon Jun 29, 2020 4:56 pm

Tomswork wrote:
Mon Jun 29, 2020 3:22 pm
I seem to remember that Phillips used a similar part in there tv sets for instant on. These are very reliable parts. I would start at the beginning if you have a signal generator.

Tom
You mean that those TVs kept their tubes charged at all times to make the TVs turn on quickly?

I don't have a signal generator, I wish I did! Actually, I've been looking for an affordable one, but haven't found one yet...

I don't understand what you mean by 'start at the beginning'. Did you mean analyzing and measuring the circuit?

Back to the part, in the forum linked earlier, someone posted a schematic, marking the HDT in green. If that's what it is, it certainly can't be a tripler as this couldn't increase the output voltage in any way.
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Re: Strange part connected to flyback of Atari SC1224

Post by Tomswork » Mon Jun 29, 2020 6:47 pm

Oh sorry if you have a signal generator you can just feed a horizontal signal in and check along the test points to just before the fly back. Will reveal weak parts. And yes some of those flyback could stay charged for years and still burn a probe tip. Samsung and Philips loved them. Must of the time you were just waiting for the tube to heat things. The part your showing looks like it charges the tube before the horizontal signal starts. The power supply is the spot with the capacitors and the regulators. That take the beating the do not cool well.

These can be got and ebay they work jds6000
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Tom

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