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

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

Postby czietz » Sat Jan 21, 2017 3:25 pm

I'm actually not sure how the circuit in the PDF would generate a proper CSYNC signal (aren't the diode polarities wrong?), but of course there are circuits which combine HSYNC and VSYNC. This may be an option for you if the composite sync is really broken on your ST. Maybe someone can either confirm that the circuit in the other forum works or recommend an alternative?

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

Postby siriushardware » Sun Jan 22, 2017 11:02 am

I have to agree that - assuming normally high, momentarily low Hsync and Vsync out from the Atari, the polarity of the diodes in that PDF article seems wrong since it will be impossible for either ST sync line to pull the monitor's csync input low through the diodes as shown oriented.

The OP of that original article seems not to have realised that his 1040ST probably already had Csync available on the monitor socket as it was a non-'M' variant.

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

Postby walterg74 » Tue Jan 24, 2017 1:46 pm

siriushardware wrote:I have to agree that - assuming normally high, momentarily low Hsync and Vsync out from the Atari, the polarity of the diodes in that PDF article seems wrong since it will be impossible for either ST sync line to pull the monitor's csync input low through the diodes as shown oriented.

The OP of that original article seems not to have realised that his 1040ST probably already had Csync available on the monitor socket as it was a non-'M' variant.


Unless his was "working" like mine is... :lol:

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

Postby siriushardware » Tue Jan 24, 2017 6:56 pm

walterg74, I don't think anyone has asked you to find out whether the components for Csync output are actually fitted in your STF.

Take a look at the attached diagram - the area ringed in red is the modulator, not fitted in an STF. The area ringed in green is the sync combiner circuit which normally gets fitted when there is no modulator. Are Q12 and its associated components actually present in your STF?

STF_MonitorOutput.png


If yes, you may have a fault on your Csync output circuit.

If not, but there vacant spaces for Q12 etc to go in, consider fitting them. None of the components are hard to find.

If not, and there is no vacant space for them, you could still build the sync combiner circuit on a small piece of stripboard and install it inside the STF.
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Re: Help with Atari STf - RGB - Cannot get video/sync

Postby walterg74 » Tue Jan 24, 2017 9:50 pm

siriushardware wrote:walterg74, I don't think anyone has asked you to find out whether the components for Csync output are actually fitted in your STF.

Take a look at the attached diagram - the area ringed in red is the modulator, not fitted in an STF. The area ringed in green is the sync combiner circuit which normally gets fitted when there is no modulator. Are Q12 and its associated components actually present in your STF?

STF_MonitorOutput.png

If yes, you may have a fault on your Csync output circuit.

If not, but there vacant spaces for Q12 etc to go in, consider fitting them. None of the components are hard to find.

If not, and there is no vacant space for them, you could still build the sync combiner circuit on a small piece of stripboard and install it inside the STF.


Ok bear with me...

Got home and tore it open...

Kinda slow, but I'm not seeing where the components are *supposed* to be... first sight I only see ONE transistor and it's labeled Q1... so first sight *seems* missing but not 100% sure...

Attaching pic of my board.

Edit: Never mind, I guess it's "in the box"..?

Lots of empty space where seems.components should be.. attaching pic of that instead.
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Re: Help with Atari STf - RGB - Cannot get video/sync

Postby czietz » Tue Jan 24, 2017 9:57 pm

Looks like the attachment (photo) wasn't uploaded...

STf board layouts and also component designators differ quite a lot, but in this example http://www.atari-wiki.com/images/c/c9/1 ... d_revD.jpg you can see the CSYNC circuit in the top center part of the PCB, where the modulator would otherwise be: Two diodes (labeled CR10 and CR11), three resistors R49..R51 and a transistor.

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

Postby walterg74 » Tue Jan 24, 2017 10:00 pm

czietz wrote:Looks like the attachment (photo) wasn't uploaded...

STf board layouts and also component designators differ quite a lot, but in this example http://www.atari-wiki.com/images/c/c9/1 ... d_revD.jpg you can see the CSYNC circuit in the top center part of the PCB, where the modulator would otherwise be: Two diodes (labeled CR10 and CR11), three resistors R49..R51 and a transistor.


Yeah sadly I'm on my phone and can't resize them (file too big error) but I just edited the post and added a different pic of the relevant area.

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

Postby walterg74 » Tue Jan 24, 2017 10:04 pm

czietz wrote:Looks like the attachment (photo) wasn't uploaded...

STf board layouts and also component designators differ quite a lot, but in this example http://www.atari-wiki.com/images/c/c9/1 ... d_revD.jpg you can see the CSYNC circuit in the top center part of the PCB, where the modulator would otherwise be: Two diodes (labeled CR10 and CR11), three resistors R49..R51 and a transistor.


Ahhh just.looked at your pic.. if it's *exactly* where the modulator goes then yes, I have nothing there contrary to your pic....
Numbering on the previous diagram threw me a bit off...

Attaching here.
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Re: Help with Atari STf - RGB - Cannot get video/sync

Postby czietz » Tue Jan 24, 2017 10:17 pm

OK, this of course explains why there is no CSYNC on your STf. I wasn't aware that there even were STfs without this circuit. Good call by siriushardware!

Probably if you simply fit the missing components, it'll work.

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

Postby walterg74 » Tue Jan 24, 2017 10:52 pm

czietz wrote:OK, this of course explains why there is no CSYNC on your STf. I wasn't aware that there even were STfs without this circuit. Good call by siriushardware!

Probably if you simply fit the missing components, it'll work.


Awesome, mystery solved :D

I actually talked to my co-worker today, he was willing to use the scope, just had to see how since he commutes.to work and I didn't want him to carry the heavy ST. Glad he won't have to! :P

Ok, I can give soldering these a go, just since there are no holes, will I just have to stand them up on the pad and solder?

More importantly, what values/part numbers do I need?

Side question 1: While it will be of course more elegant to install them there, technically could I also do it on the cable directly from the outside? I mean, the schematic shows the signals are pulled from vsync and "sync/composite" anyway? (Or would that just be a chicken and egg thing?) Just curiosity anyway.

Side question 2: Since I already opened this.. should I bother upgrading TOS? Seems to have 6 chip 1.0 socketed...
Last edited by walterg74 on Tue Jan 24, 2017 11:37 pm, edited 1 time in total.

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

Postby siriushardware » Tue Jan 24, 2017 11:33 pm

At least we're getting somewhere. Sorry the component numbers don't match those in the csync circuit in that diagram I included earlier but the Csync circuit is, as has been pointed out, usually where the missing modulator would be.

So the equivalent components in your hardware are Q8, R49, R50, R51, CR10 and CR11.

We can say that
Q8 = 2N3904
CR10 and CR11 are 1N914 diodes

The resistors are
10K ohms
100 ohms
150 ohms

If you can show us a clear picture of the other side of the PCB in that area we should be able to work out which of those values corresponds to R49, R50 and R51.

Or, if you can use the ohms range on your multimeter:

The 10K resistor is the only one which has one end connected to the +5V rail
The 150R resistor is the only one which has one end connected to ground / 0V
The 100R resistor is the only one which has one end connected to the monitor socket pin 2.

A little bit of investigation with your multimeter should tell you which resistor goes in which physical position.

In your photo, it looks to me like the right hand end of R51 goes to the large 0V / earth plane on the top side of the PCB. If so, R51 = 150R. You'll have to work out the other two.

Yes, you should be able to get away with tack-soldering the components to the upper pads on the PCB, as the through-hole connections to the other side are made by copper sleeves which line the insides of the holes.

If you do that, keep the component leads very short and don't let them sink more than a couple of mm into the depth of the PCB otherwise they will stick through out of the underside and may fold over and short to each other or other nearby pads. Just to be clear: The holes are actually there, they are just filled with solder. If you want to fit the components properly, use a desolder pump to clear the holes, then fit the components in the conventional fashion. You might want to fold some masking tape over the inner and outer faces of the plastic enclosure nearby while you're soldering the components - when working that close to plastic enclosures, it's very easy to be so focused on the tip of the iron that you don't realise the barrel of the iron is melting something nearby.

Edit: You could build the Csync circuit externally, but the +5V supply that it requires is only available inside the STF, not on the monitor socket. Since you've already been provided with a ready made place for the components to go, you should take the opportunity to fit them there.
Last edited by siriushardware on Wed Jan 25, 2017 12:11 am, edited 1 time in total.

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

Postby walterg74 » Wed Jan 25, 2017 12:05 am

siriushardware wrote:At least we're getting somewhere. Sorry the component numbers don't match those in the csync circuit in that diagram I included earlier but the Csync circuit is, as has been pointed out, usually where the missing modulator would be.

So the equivalent components in your hardware are Q8, R49, R50, R51, CR10 and CR11.

We can say that
Q8 = 2N3904
CR10 and CR11 are 1N914 diodes

The resistors are
10K ohms
100 ohms
150 ohms

If you can show us a clear picture of the other side of the PCB in that area we should be able to work out which of those values corresponds to R49, R50 and R51.


Ok, disassembled and took a pic. Is that good enough?

If not I don't mind the multimeter but two very niob/stylid questions:

1) I assume I measure with the ST powered on...
2) red lead against the test point, but blac/gnd lead against what?
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Re: Help with Atari STf - RGB - Cannot get video/sync

Postby walterg74 » Wed Jan 25, 2017 12:18 am

Ok so of I read this correctly, inverted, left is right and viceversa. So the "three component" side of the transistor has the 2 diodes and R49.
Since according to the traces R49 is connected between the transistor's base and collector, according to the schematics you showed mean that would mean R49 is the 10k one.

The other two both have one end connected to the emitter, with the one closest to the transistor, R50, seeming to be connected to a pin on the DIN connector, making it the 100 one, and the one farthest away, R51 seeming to go to a pad that I don't know what it is but I guess it's GND and that's the 150 one?

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

Postby siriushardware » Wed Jan 25, 2017 12:39 am

That's a good picture, so I can tell you that

R49=10K
R50=100R
R51=150R

For future reference, you always do resistance measurements with the power OFF. For this purpose you would use the lowest ohms range your meter has, or a 'Buzzer / Continuity' setting if it has that.

I'm happy to talk you through how you would use your meter to work out which was which, but if you just wanted to know which resistor value goes where, your most recent picture provided enough information for us to be able to work it out without having to trace with a meter. In any case you seem to have done a good job tracing by eye.

Ignore what I originally posted (and since edited out) about the inversion / non inversion of the Hysnc / Vsync signals: My brain was switched off when I wrote that and your original hypothesis was actually correct. As stated in the edited version of my previous post, the main problem with trying to use the Csync circuit externally is the lack of a 5V supply for it on the monitor socket.

You've done a good job working out the resistors by yourself.

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

Postby walterg74 » Wed Jan 25, 2017 12:58 am

siriushardware wrote:That's a good picture, so I can tell you that

R49=10K
R50=100R
R51=150R

For future reference, you always do resistance measurements with the power OFF. For this purpose you would use the lowest ohms range your meter has, or a 'Buzzer / Continuity' setting if it has that.

I'm happy to talk you through how you would use your meter to work out which was which, but if you just wanted to know which resistor value goes where, your most recent picture provided enough information for us to be able to work it out without having to trace with a meter. In any case you seem to have done a good job tracing by eye.

Ignore what I originally posted (and since edited out) about the inversion / non inversion of the Hysnc / Vsync signals: My brain was switched off when I wrote that and your original hypothesis was actually correct. As stated in the edited version of my previous post, the main problem with trying to use the Csync circuit externally is the lack of a 5V supply for it on the monitor socket.

You've done a good job working out the resistors by yourself.


Well... couldn't have gotten here without the guidance of you guys! :D

Regarding measuring, I knew that about measuring resistance, but my confusion was because in the above part, I didn't actually have to measure resistance, mine are not there. Or at least I thought that what you wanted me to do was to measure to see where I had the 10V point and the 0V point to know where to fit the resistors, and not measure resistance. I guess I just didn't understand what you wanted me todo with the multimeter?

I guess now also the hard part is control the anxiousness of running out tomorrow to get the parts and do it with a cheap dollar iron, or wait till next week when I will receive my recently purchased Hakko FX-888D... :|

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

Postby siriushardware » Wed Jan 25, 2017 1:24 am

You understood correctly that I meant you to use your meter to find out which of certain pairs of points were directly connected together, in other words to find out which ones had zero resistance between them.

In the old days ... (I am pretty old school) meters only had volts, ohms, and amps on them so you would use the resistance range to search for direct connections between two points, even though what you would actually be looking for in that instance was zero resistance.

More recently, meters have tended to come with extra ranges including 'continuity', which basically sounds a buzzer whenever the probes are connected together either directly, or via a wire or PCB track. That would have been fine to use for this purpose as well. But you got there anyway by working it out logically by tracing the tracks by eye, which is exactly the same way that I did it.

Your STF has already survived largely unharmed for more than three decades now, so my instinct would be to let it be for one more week until you have improved soldering gear available - but if you can't wait you could always tack-solder the parts temporarily to the upper pads to see if it works and then fit them neatly and permanently when you receive your 'good' iron.

Whatever you do, let us know how it works out. We love a happy ending.

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

Postby walterg74 » Wed Jan 25, 2017 2:03 am

siriushardware wrote:You understood correctly that I meant you to use your meter to find out which of certain pairs of points were directly connected together, in other words to find out which ones had zero resistance between them.

In the old days ... (I am pretty old school) meters only had volts, ohms, and amps on them so you would use the resistance range to search for direct connections between two points, even though what you would actually be looking for in that instance was zero resistance.

More recently, meters have tended to come with extra ranges including 'continuity', which basically sounds a buzzer whenever the probes are connected together either directly, or via a wire or PCB track. That would have been fine to use for this purpose as well. But you got there anyway by working it out logically by tracing the tracks by eye, which is exactly the same way that I did it.

Your STF has already survived largely unharmed for more than three decades now, so my instinct would be to let it be for one more week until you have improved soldering gear available - but if you can't wait you could always tack-solder the parts temporarily to the upper pads to see if it works and then fit them neatly and permanently when you receive your 'good' iron.

Whatever you do, let us know how it works out. We love a happy ending.


Thanks, will do!

It was in fact, surprisingly nice except for a few bits of dust here and there.

The only bad thing was the rust patches on the top side of the top metal shielding and the top shielding of the floppy drive as well... now that I'd like to get rid of... (and why on earth does that happen anyway and why only to the top side? (Althouh great it's not on the "inside side" as well...
Any elegant solutions before I dremel them to hell..? :roll:

What about TOS? Worth upgrading it?

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

Postby czietz » Wed Jan 25, 2017 5:52 pm

I'm just curious, particularly so as if never seen a board without the CSYNC circuit. Could you tell us the part number and revision? Usually it's printed somewhere on the board in the vicinity of an Atari logo: The part number is a "C" followed by several digits and it says "Rev. X" for the revision number.

walterg74 wrote:What about TOS? Worth upgrading it?


TOS 1.00 has some nasty bugs. I'd upgrade to 1.04. (TOS 2.06 is also possible on an STf, but requires some hardware modifications.) But whether it's really worth the upgrade of course depends on what you will do with your ST.

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

Postby walterg74 » Wed Jan 25, 2017 6:14 pm

czietz wrote:I'm just curious, particularly so as if never seen a board without the CSYNC circuit. Could you tell us the part number and revision? Usually it's printed somewhere on the board in the vicinity of an Atari logo: The part number is a "C" followed by several digits and it says "Rev. X" for the revision number.

walterg74 wrote:What about TOS? Worth upgrading it?


TOS 1.00 has some nasty bugs. I'd upgrade to 1.04. (TOS 2.06 is also possible on an STf, but requires some hardware modifications.) But whether it's really worth the upgrade of course depends on what you will do with your ST.



You mean the general board number and rev? I don't think it's anything strange, I have seen it mentioned in other threads. It is:

C070523-001 REV.D

Regarding TOS, will only do games. Heard comments about uograding from 1.02 to 1.04 or keep 1.02, but not about the same for 1.00...

Also what about "bad dma"? Is that something I should be concerned about ir does it only affect STe machines?

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

Postby siriushardware » Wed Jan 25, 2017 6:34 pm

If you intend eventually to use a modern 'Hard drive' like a CosmosEx or Ultrasatan (other HDD solutions also exist) then I would upgrade to TOS 1.4. My original ST, which I used with an external HDD, had TOS 1.0. When I updated it to TOS1.4 the increase in the speed of HDD access was astounding.

If your TOS is a 6-chip TOS then you can program your chosen TOS into 6 * 27C256 eproms and drop them straight in.

If you still want to be able to use TOS 1.0 as well, the simple / cheap way to do that is to program the code for the old TOS into the lower halves of 6 27C512 eproms, and the code for the new TOS into the upper halves of the same six eproms.

Fit these in the sockets with the highest address pin (Pin 1) on each 27C512 bent straight out sideways so it does not go into the socket, wire all those pin 1s together and then wire a switch which can be used to take all the interwired pins 1s either to 0V or to 5V.

With a switching method this crude the machine will crash instantly if you switch TOS while it is running, so you have to put the switch in the required position before powering the machine on, or switch it over while holding down reset.

One thing at a time, though: Sort the Csync problem first.

On the subject of the DMA, there are some strongly held opposing views about this especially with respect to the STe: But the majority of people (myself included) have never had reason to change the DMA IC in a 'Normal' ST so I would just leave well alone.

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

Postby czietz » Wed Jan 25, 2017 6:39 pm

walterg74 wrote:
You mean the general board number and rev? I don't think it's anything strange, I have seen it mentioned in other threads. It is:

C070523-001 REV.D


So, by coincidence, it's the same board number and revision as the one that I already linked previously:
http://www.atari-wiki.com/images/c/c9/1 ... d_revD.jpg

You can see that in the photo the components for CSYNC are fitted. Very interesting!

walterg74 wrote:
Regarding TOS, will only do games. Heard comments about uograding from 1.02 to 1.04 or keep 1.02, but not about the same for 1.00...


TOS 1.00 is much more buggy than 1.04 or even 1.02. For example, using a harddisk with 1.00 is not recommended -- should you ever plan to do this.
However, (floppy based) games are probably less affected by TOS bugs.

walterg74 wrote:
Also what about "bad dma"? Is that something I should be concerned about ir does it only affect STe machines?

[/quote]

Imho this "bad DMA" thing is a little over-hyped. It affects some (but by far not all!) STe machines with a certain version of the DMA chip and usually only when used together with a modern harddisk replacement such as UltraSatan. But to my knowledge it has never been conclusively proven that it's really the DMA chip that is "bad" per se. The most detailed investigation in this matter was done by exxos: http://www.exxoshost.co.uk/atari/last/DMAfix/. He also advises things that can be done to a STf DMA if required.

Of course all ICs and all circuits age, so there might be some chips in your STf as well that don't have the same specs as they had 30 years ago. However, I haven't heard of any particularly problematic ICs (DMA or others) in STfs in general.

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

Postby walterg74 » Wed Jan 25, 2017 6:50 pm

siriushardware wrote:If you intend eventually to use a modern 'Hard drive' like a CosmosEx or Ultrasatan (other HDD solutions also exist) then I would upgrade to TOS 1.4. My original ST, which I used with an external HDD, had TOS 1.0. When I updated it to TOS1.4 the increase in the speed of HDD access was astounding.

If your TOS is a 6-chip TOS then you can program your chosen TOS into 6 * 27C256 eproms and drop them straight in.

If you still want to be able to use TOS 1.0 as well, the simple / cheap way to do that is to program the code for the old TOS into the lower halves of 6 27C512 eproms, and the code for the new TOS into the upper halves of the same six eproms.

Fit these in the sockets with the highest address pin (Pin 1) on each 27C512 bent straight out sideways so it does not go into the socket, wire all those pin 1s together and then wire a switch which can be used to take all the interwired pins 1s either to 0V or to 5V.

With a switching method this crude the machine will crash instantly if you switch TOS while it is running, so you have to put the switch in the required position before powering the machine on, or switch it over while holding down reset.

One thing at a time, though: Sort the Csync problem first.

On the subject of the DMA, there are some strongly held opposing views about this especially with respect to the STe: But the majority of people (myself included) have never had reason to change the DMA IC in a 'Normal' ST so I would just leave well alone.



Thanks for the suggestion. I don't think I'll do other things on *this* Atari at least besides games. I do have an HxC floppy emulator ready to be tested as well.
In any case besides this machine I also have two other PAL ones. A 1040STFM, and a 520STE upgraded to 4MB.

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

Postby walterg74 » Wed Jan 25, 2017 7:01 pm

czietz wrote:
So, by coincidence, it's the same board number and revision as the one that I already linked previously:
http://www.atari-wiki.com/images/c/c9/1 ... d_revD.jpg

You can see that in the photo the components for CSYNC are fitted. Very interesting!



Ha! True.. we could have also (sort of) figured out which R is which from that pic :)

One difference I see besides that is my machine does not have that huge-ass capacitor above the memory... not sure what it's for but the ine in that pictute has that cap between a point above the memory and the other leg on JP4, to the left of the glue shielding, right below the PSU connector, with the red and blue intertwined cables hooked up to where a cap goes (C35?).

On my board I have no such thing, and the red cable goes to JP4 and I think the blue is on JP5, on that place marked C35 I actually have a small cap.

Is that any type of mod on your linked one or what?

czietz wrote:TOS 1.00 is much more buggy than 1.04 or even 1.02. For example, using a harddisk with 1.00 is not recommended -- should you ever plan to do this.
However, (floppy based) games are probably less affected by TOS bugs.


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

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

Postby czietz » Wed Jan 25, 2017 7:41 pm

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.

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

Postby ijor » Wed Jan 25, 2017 9:29 pm

walterg74 wrote:So I guess a 1.00 to 1.04 wold be a good choice?


With all due respect to my friend Christian and others, I beg to differ a little with the recommendation. I used (and still use) TOS 1.0 with hard disk for years without any problems. Yes, it is buggy and it's not the fastest, but with the right drivers and as long as you limit yourself to small partitions, then it should be ok. If you do want to use big partitions, then upgrading TOS is a must.

On the other hand, if you have the tools and the knowledge to upgrade without problems, and you don't care too much about compatibility with older original programs, then there is no reason to not upgrade. And if you can install some kind of dual selectable TOS versions as suggested already, then, of course, that's the ideal setup.


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