Atari STE Power Up

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friijy2001
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Atari STE Power Up

Post by friijy2001 » Fri Jun 11, 2021 7:41 am

Not sure but this looks like a reset cap issue, any thoughts? This is one of my STE's I am trying to get back to health.

I have done the main fixes except the reset cap fix but wanted to see if it could be anything else video related. I have also tried two recapped PSU's too. I can post pics of the board if needed later :)

Via RF I get this screen first (moving)

IMG_6402.JPG
IMG_6402.JPG (365.52 KiB) Viewed 138 times

It then does this

IMG_6403.JPG
IMG_6403.JPG (357.31 KiB) Viewed 138 times

And then this, image is stable and as you would expect from rf a little fuzzy.

IMG_6401.JPG
IMG_6401.JPG (503.38 KiB) Viewed 138 times

However the main problems starts when I plug in the RGB Scart cable into the monitor socket, it sometimes boots and goes to desktop.
Other times it works and then shortly after the image starts wobbling
Other times I get a rolling picture
Other times it will be off screen
Other time I get this

IMG_6406.JPG
IMG_6406.JPG (132.31 KiB) Viewed 138 times

I plug in the RF I get the above again.
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friijy2001
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Re: Atari STE Power Up

Post by friijy2001 » Fri Jun 11, 2021 9:07 am

Oh also to add, everything else works fine the drive and it even loads software in the background.

If it was an STFM I would look at video recap or inspecting around the shifter so a little puzzled :?:
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exxos
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Re: Atari STE Power Up

Post by exxos » Fri Jun 11, 2021 9:24 am

What RGB cable are you using ? Doing to reset caps doesn't take long, so just get it done and save some headaches.
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viewtopic.php?f=17&t=1585 Have you done the Mandatory Fixes ?

friijy2001
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Re: Atari STE Power Up

Post by friijy2001 » Fri Jun 11, 2021 9:27 am

It’s an RGB to scart cable from cool novelties, found them to be the best tbh. Are you thinking to try another cable?
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Re: Atari STE Power Up

Post by exxos » Fri Jun 11, 2021 9:33 am

I half recall someone else having this issue recently but can't remember the outcome :( have you taken the large chip out from under the PSU and cleaned it, maybe resolder the socket..
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Re: Atari STE Power Up

Post by rubber_jonnie » Fri Jun 11, 2021 9:55 am

I'm quite surprised that you even got a signal via RF on that modern TV!

If you've done all the other fixes, then I would just do the reset caps to cover all bases. It sounds like power isn't a problem, but IIRC, not all RGB SCART cables are created equal so it may be worth also trying a different one. Similarly some modern TVs don't play nice with older scart.

I have a Coolnovelties cable and it works just fine.

BTW, have you pulled the mainboard and checked the solder under the video out connector to make sure it is good? You could also try a VGA adaptor, see if you get a different result on a VGA display, providing it supports 15Khz.
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Steve
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Re: Atari STE Power Up

Post by Steve » Fri Jun 11, 2021 10:03 am

You mentioned you have other Ataris? I assume this TV picks up SCART RGB from those other units using the same cable OK? (Just to rule out any TV issue)
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Re: Atari STE Power Up

Post by tzok » Fri Jun 11, 2021 10:13 am

Some TV doesn't support RGB over SCART, but even if they do, there are several problems.

1. STfm doesn't have a composite sync signal used by SCART RGB, instead composite video signal is used.
2. Some TV, have support for RGB mode, but make only automatic switching between composite and RGB. In RGB mode, the composite sync signal is supplied by the same pin, as composite video signal is supplied in composite mode. There is another pin for switching between composite and RGB, but Atari doesn't have appropriate voltage on the monitor output to correctly switch the SCART to the RGB mode. The current output of 12V pin is far too low to do that.

friijy2001
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Re: Atari STE Power Up

Post by friijy2001 » Fri Jun 11, 2021 10:29 am

exxos wrote:
Fri Jun 11, 2021 9:33 am
I half recall someone else having this issue recently but can't remember the outcome :( have you taken the large chip out from under the PSU and cleaned it, maybe resolder the socket..
I will give that a try :)
rubber_jonnie wrote:
Fri Jun 11, 2021 9:55 am
BTW, have you pulled the mainboard and checked the solder under the video out connector to make sure it is good? You could also try a VGA adaptor, see if you get a different result on a VGA display, providing it supports 15Khz.
I went one further than that and replaced the video out connector, still the same issue.
Steve wrote:
Fri Jun 11, 2021 10:03 am
You mentioned you have other Ataris? I assume this TV picks up SCART RGB from those other units using the same cable OK? (Just to rule out any TV issue)
The cable works with the other machines so its not the cable, this is fun :)
tzok wrote:
Fri Jun 11, 2021 10:13 am
Some TV doesn't support RGB over SCART, but even if they do, there are several problems.

1. STfm doesn't have a composite sync signal used by SCART RGB, instead composite video signal is used.
2. Some TV, have support for RGB mode, but make only automatic switching between composite and RGB. In RGB mode, the composite sync signal is supplied by the same pin, as composite video signal is supplied in composite mode. There is another pin for switching between composite and RGB, but Atari doesn't have appropriate voltage on the monitor output to correctly switch the SCART to the RGB mode. The current output of 12V pin is far too low to do that.
This is a Plasma TV and works great with RGB.

Thank you for all the suggestions guys, I'll do the reset cap fix and try the big chip under the PSU. (out of curiosity what is that chip?) I may have a spare so will give that a go too.

It is weird as it work fine via RGB Scart but after a short time it starts playing up, maybe the chip has been damaged by a bad PSU over time etc...
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friijy2001
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Re: Atari STE Power Up

Post by friijy2001 » Fri Jun 11, 2021 10:40 am

Another screen over RGB scart just to add to the library :)

3A2F36F3-B099-4787-979A-237387A721E6.jpeg
3A2F36F3-B099-4787-979A-237387A721E6.jpeg (898.25 KiB) Viewed 100 times

This is static but sometimes it rolls
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