Strange part connected to flyback of Atari SC1224

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sandord
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Strange part connected to flyback of Atari SC1224

Post by sandord » Sun Jan 06, 2019 6:37 pm

I've just opened up my beloved Atari SC1224 monitor to make a revision parts list. I'm going to replace all electroylic caps, the HOT, VOT, the rectifier, PSU switching power regulator and the LOPT (flyback).

When inspecting the latter, I found that, to my surprise, there's strange part connected to it. I haven't seen any of these before. Anyone know that it is?

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PaulJ
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Re: Strange part connected to flyback of Atari SC1224

Post by PaulJ » Sun Jan 06, 2019 6:44 pm

My guess is its a triple : A string of diodes and capacitors designed to boost the output of the flyback
transformer to the level required for the picture tube.

Just a guess though. :?: :?: :?:

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Re: Strange part connected to flyback of Atari SC1224

Post by exxos » Sun Jan 06, 2019 6:50 pm

Tripler.
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Re: Strange part connected to flyback of Atari SC1224

Post by sandord » Sun Jan 06, 2019 6:58 pm

Okay, thanks guys.

I was looking to fix up the monitor with a fresh flyback but now I'll have to find a tripler replacement as well... that is, if I want to give this baby a chance of a long life ahead.

Either way, I think it'll be difficult to connect the new flyback to the tripler. The wire that runs from the flyback to the tripler and from the tripler to the suction cup are very tightly mounted. It doesn't look like there's a way to get them off (let alone replace them) without causing damage.

I guess I should have looked for a flyback that has the tripler integrated in it :roll:

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Re: Strange part connected to flyback of Atari SC1224

Post by sandord » Sun Jan 06, 2019 7:43 pm

So I think I'm going to have to find a suitable replacement for the tripler. I've seen some of those around, just need to find the specs of the original one but sadly it doesn't have any writings other than OT4 and the service manual doesn't mention it as far as I can tell.

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Re: Strange part connected to flyback of Atari SC1224

Post by exxos » Sun Jan 06, 2019 8:05 pm

Keep the same tripler and replace the flyback if you must ?
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Re: Strange part connected to flyback of Atari SC1224

Post by sandord » Sun Jan 06, 2019 8:12 pm

exxos wrote:
Sun Jan 06, 2019 8:05 pm
Keep the same tripler and replace the flyback if you must ?
I'm afraid that the tripler might have worn off, as they tend to. Replacing just the flyback is kind of like going half way.

But eventually, if I can't find a suitable tripler replacement, that's just how it's going to have to be.

But not yet :)

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Re: Strange part connected to flyback of Atari SC1224

Post by sandord » 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.

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Re: Strange part connected to flyback of Atari SC1224

Post by sandord » Mon Jan 07, 2019 9:47 am

For now, I'm aiming at replacing the flyback and leaving the tripler in place.

Since I'll need to cut the anode cup from the new flyback and connect the new flyback to the tripler, I'm going to have to connect the two HV wires while maintaining proper insulation.

I found these instructions today: https://rimstar.org/equip/hvwiring.htm.

Looking for high voltage butt splice connectors I can only find stuff like this: https://uk.rs-online.com/web/p/crimp-bu ... s/0533667/

But of course this won't suffice since its only rated for 600V (what does the "Dielectric Strength 7.5kV" mean though?).

Any tips?

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Re: Strange part connected to flyback of Atari SC1224

Post by exxos » Mon Jan 07, 2019 11:29 am

sandord wrote:
Mon Jan 07, 2019 9:47 am
But of course this won't suffice since its only rated for 600V (what does the "Dielectric Strength 7.5kV" mean though?).
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..
4MB STFM 1.44 FD- VELOCE+ 020 STE - 4MB STE 32MHz - STFM 16MHz - STM - MEGA ST - Falcon 030 CT60 - Atari 2600 - Atari 7800 - Gigafile - SD Floppy Emulator - PeST - HxC - CosmosEx - Ultrasatan - various clutter

https://www.exxoshost.co.uk/atari/ All my hardware guides - mods - games - STOS
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