Help with Atari STf - RGB - Cannot get video/sync

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walterg74
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Re: Help with Atari STf - RGB - Cannot get video/sync

Postby walterg74 » Wed Jan 25, 2017 10:17 pm

czietz wrote:You'd have to ask the person that took the photo if there were any non-original mods done to the Atari. However, there indeed seem to be differences in regard to that capacitor on different Rev. D boards. (Also note: different PCB manufacturers.)

http://www.atari-wiki.com/images/6/62/S ... _exxos.jpg
http://www.atari-wiki.com/images/c/c9/1 ... d_revD.jpg
http://www.atari-wiki.com/images/9/91/S ... _D_Dio.jpg (this probably is what you have?)

So I guess a 1.00 to 1.04 wold be a good choice?


Personally, I would definitely do the upgrade; however -- as I already wrote -- the bugs in TOS 1.00 might not be that critical if you use the machine for games only.

EDIT: An old Atari technical note recommends increasing that capacitor, particularly if a certain type of power supply is installed. This may be the reason for different caps on boards of the same revision.



Yeah, that's pretty much what I have with the differences of no modulator (or Csync circuit :lol: ), full med instead of half, and less components inside the center box (I guess those are for the composite/rf output?).

siriushardware
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Re: Help with Atari STf - RGB - Cannot get video/sync

Postby siriushardware » Thu Jan 26, 2017 12:25 am

There were a few games for which the original release (working on TOS 1.0) was broken by later TOS versions. Arkanoid was one such, as it read the mouse X position from a system variable which moved to a different memory location in later TOS versions.

In theory all software written to be compatible with TOS 1.4 should also have been written to maintain compatibility with all earlier TOS versions. Software written when TOS 1.0 was current may fail on later, at the time still unknown TOS versions. For that reason at least, keeping your old TOS in one of your small fleet of STs may not be a bad idea.

When I was running TOS 1.0 and a HDD originally, it all just worked and I was never aware that TOS 1.0 supposedly had some bad bugs including some relating to HDD access. It was only when I upgraded to TOS 1.4 that I noticed what a huge difference it made to HDD access times. but upgrading also broke some of my software which had previously worked, like the aforementioned Arkanoid.

So to summarise: For maximum commercial (game) software compatibility, run the earliest TOS. But if there are specific features or fixes in a later TOS which you know you need, use a later TOS. Or in your case, just keep both in different machines.

walterg74
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Re: Help with Atari STf - RGB - Cannot get video/sync

Postby walterg74 » Thu Jan 26, 2017 12:35 am

siriushardware wrote:There were a few games for which the original release (working on TOS 1.0) was broken by later TOS versions. Arkanoid was one such, as it read the mouse X position from a system variable which moved to a different memory location in later TOS versions.

In theory all software written to be compatible with TOS 1.4 should also have been written to maintain compatibility with all earlier TOS versions. Software written when TOS 1.0 was current may fail on later, at the time still unknown TOS versions. For that reason at least, keeping your old TOS in one of your small fleet of STs may not be a bad idea.

When I was running TOS 1.0 and a HDD originally, it all just worked and I was never aware that TOS 1.0 supposedly had some bad bugs including some relating to HDD access. It was only when I upgraded to TOS 1.4 that I noticed what a huge difference it made to HDD access times. but upgrading also broke some of my software which had previously worked, like the aforementioned Arkanoid.

So to summarise: For maximum commercial (game) software compatibility, run the earliest TOS. But if there are specific features or fixes in a later TOS which you know you need, use a later TOS. Or in your case, just keep both in different machines.


Thanks for sharing the info. I will have to re-check just in case, but I believe my PAL 1040 STFM was running 1.02, if that's the case I have both versions (no 1.04). Also I believe the 520STE had 1.62.

strygo
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Re: Help with Atari STf - RGB - Cannot get video/sync

Postby strygo » Sun Jun 10, 2018 2:26 pm

Hi there! I may have the exact same problem as the OP.

I recently picked up a 60hz Atari 1040STF and have been wracking my brain trying to figure out why I couldn't get a signal to display on my TV, even though I see one just fine on my SC1224. I tried two different SCART cables without success. I have not yet verified the absence of a sync circuit - that's my next step.

walterg74: did you have any success adding a sync circuit to your board? And for others: are we both just unlikely? If I were to pick up a second system, what are the odds it will have this same problem?

Thank you for your time.

- Steve
Last edited by strygo on Sun Jun 10, 2018 5:19 pm, edited 1 time in total.

walterg74
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Re: Help with Atari STf - RGB - Cannot get video/sync

Postby walterg74 » Sun Jun 10, 2018 5:17 pm

strygo wrote:Hi there! I may have the exact same problem as the OP.

I recently picked up a 60hz Atari 1040STF and have been wracking my braining trying to figure out why I couldn't get a signal to display on my TV, even though I see one just fine on my SC1224. I tried two different SCART cables without success. I have not yet verified the absence of a sync circuit - that's my next step.

walterg74: did you have any success adding a sync circuit to your board? And for others: are we both just unlikely? If I were to pick up a second system, what are the odds it will have this same problem?

Thank you for your time.

- Steve



Hi Steve, unfortunately I just didn’t grt to it as I didn’t yet have the tools then and then also have a lotnof machines in my collection and a few to fix something or other.

However, having said that, I’m convinced that adding the few
Missing components will solve the issue.

strygo
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Re: Help with Atari STf - RGB - Cannot get video/sync

Postby strygo » Sun Jun 10, 2018 6:54 pm

Thanks walterg74. I did a little more digging:

Upon opening both SCART plugs, I discovered that the one I got from Retro Computer Shack has a resistor on the sync line and the other from kabelheinz does not (SCART pin 20). I would assume that a resistor is necessary for converting TTL csync to 75ohm csync on the STF model.

I also opened up my STF and it looks a bit different than walterg74's. It is a Rev. C1 and similar to his, the area where the RF Modulator is on the STFM is completely empty. Photos of both are here: https://imgur.com/a/foyZElX

Does anyone know if mine is also missing csync based on this photo? Thank you for your help!

- Steve

czietz
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Re: Help with Atari STf - RGB - Cannot get video/sync

Postby czietz » Sun Jun 10, 2018 7:04 pm

strygo wrote:Does anyone know if mine is also missing csync based on this photo? Thank you for your help!


It is missing. The circuit to generate CSYNC consists of transistor Q12 and the adjacent resistors and diodes -- all unpopulated on your board. You can see here, albeit on a Rev. B board, how it looks when CSYNC is present: https://www.exxoshost.co.uk/forum/downl ... hp?id=2210

strygo
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Re: Help with Atari STf - RGB - Cannot get video/sync

Postby strygo » Sun Jun 10, 2018 7:22 pm

Doh! If I were to pick up another STF, what's the likelihood of it also missing this circuitry? I'd like to think I can populate the board, but I've not had a ton of success any time I attempt to use a soldering iron. :)


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