Search found 48 matches

by walterg74
Sun Jun 10, 2018 5:17 pm
Forum: Hardware
Topic: Help with Atari STf - RGB - Cannot get video/sync
Replies: 85
Views: 27381

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

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....
by walterg74
Thu Jan 26, 2017 12:35 am
Forum: Hardware
Topic: Help with Atari STf - RGB - Cannot get video/sync
Replies: 85
Views: 27381

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

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 compatibl...
by walterg74
Wed Jan 25, 2017 10:17 pm
Forum: Hardware
Topic: Help with Atari STf - RGB - Cannot get video/sync
Replies: 85
Views: 27381

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

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/ST_Motherboard...
by walterg74
Wed Jan 25, 2017 7:01 pm
Forum: Hardware
Topic: Help with Atari STf - RGB - Cannot get video/sync
Replies: 85
Views: 27381

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

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/c9/1040stf_motherboard_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) fi...
by walterg74
Wed Jan 25, 2017 6:50 pm
Forum: Hardware
Topic: Help with Atari STf - RGB - Cannot get video/sync
Replies: 85
Views: 27381

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

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. I...
by walterg74
Wed Jan 25, 2017 6:14 pm
Forum: Hardware
Topic: Help with Atari STf - RGB - Cannot get video/sync
Replies: 85
Views: 27381

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

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&...
by walterg74
Wed Jan 25, 2017 2:03 am
Forum: Hardware
Topic: Help with Atari STf - RGB - Cannot get video/sync
Replies: 85
Views: 27381

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

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 th...
by walterg74
Wed Jan 25, 2017 12:58 am
Forum: Hardware
Topic: Help with Atari STf - RGB - Cannot get video/sync
Replies: 85
Views: 27381

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

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 throu...
by walterg74
Wed Jan 25, 2017 12:18 am
Forum: Hardware
Topic: Help with Atari STf - RGB - Cannot get video/sync
Replies: 85
Views: 27381

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

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 woul...
by walterg74
Wed Jan 25, 2017 12:05 am
Forum: Hardware
Topic: Help with Atari STf - RGB - Cannot get video/sync
Replies: 85
Views: 27381

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

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, R5...
by walterg74
Tue Jan 24, 2017 10:52 pm
Forum: Hardware
Topic: Help with Atari STf - RGB - Cannot get video/sync
Replies: 85
Views: 27381

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

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 willin...
by walterg74
Tue Jan 24, 2017 10:04 pm
Forum: Hardware
Topic: Help with Atari STf - RGB - Cannot get video/sync
Replies: 85
Views: 27381

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

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/c9/1040stf_motherboard_revD.jpg you can see the CSYNC circuit in the top center part of the PCB, where the modulator would...
by walterg74
Tue Jan 24, 2017 10:00 pm
Forum: Hardware
Topic: Help with Atari STf - RGB - Cannot get video/sync
Replies: 85
Views: 27381

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

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/c9/1040stf_motherboard_revD.jpg you can see the CSYNC circuit in the top center part of the PCB, where the modulator would...
by walterg74
Tue Jan 24, 2017 9:50 pm
Forum: Hardware
Topic: Help with Atari STf - RGB - Cannot get video/sync
Replies: 85
Views: 27381

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

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 normall...
by walterg74
Tue Jan 24, 2017 1:46 pm
Forum: Hardware
Topic: Help with Atari STf - RGB - Cannot get video/sync
Replies: 85
Views: 27381

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

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 tha...
by walterg74
Sat Jan 21, 2017 2:04 pm
Forum: Hardware
Topic: Help with Atari STf - RGB - Cannot get video/sync
Replies: 85
Views: 27381

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

For the VSYNC pulse it's best to use pulse triggering, i.e. letting the scope only trigger to pulses of a certain duration. Other than that there's nothing challenging in measuring the composite sync signal. Ok, sounds good! Crossing fingers I'll be able to find something... As a curiosity (since I...
by walterg74
Sat Jan 21, 2017 1:20 pm
Forum: Hardware
Topic: Help with Atari STf - RGB - Cannot get video/sync
Replies: 85
Views: 27381

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

OK, measurement done on my European 1040STf, directly at the monitor connector, pin 2. This is the horizontal timing -- an entire line (including HSYNC) takes 64 µs, the HSYNC pulse itself is about 5 µs long: NewFile26.png Note: Horizontal timing will vary slightly with an US model. This the the VS...
by walterg74
Sat Jan 21, 2017 12:27 pm
Forum: Hardware
Topic: Help with Atari STf - RGB - Cannot get video/sync
Replies: 85
Views: 27381

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

If I can get someone with a scope, what should I tell them to measure/look for on pin 2? Voltages and timings, basically. Also whether there is any ripple or over-shoot/under-shoot in the signal. The composite sync signal should be high most of the time, with a regular sequence of short low pulses ...
by walterg74
Sat Jan 21, 2017 11:49 am
Forum: Hardware
Topic: Help with Atari STf - RGB - Cannot get video/sync
Replies: 85
Views: 27381

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

I still think the most probable cause is that there is something wrong with the composite sync signal. Sorry, but after all this time I don't fully remember what you already did to locate the problem. If I recall correctly, the SCART cable and TV work with another ST, so they are confirmed to be go...
by walterg74
Sat Jan 21, 2017 2:25 am
Forum: Hardware
Topic: Help with Atari STf - RGB - Cannot get video/sync
Replies: 85
Views: 27381

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

Yes, the SM124 works with separate sync lines, see for example page 9 in the service manual http://dev-docs.atariforge.org/files/SM124_Service_Manual_MT-21.pdf . So the H and V sync lines are fine. (One could of course think of very exotic faults in the GLUE chip that cause H and V sync only to fai...
by walterg74
Fri Jan 20, 2017 11:04 pm
Forum: Hardware
Topic: Bouncing screen on STF with RGB Scart
Replies: 29
Views: 15684

Re: Bouncing screen on STF with RGB Scart

Hi Ian, should this one work on an STf ? I could not get it to work with any of my cables, on a 1084S-D2 monitor (not with scart + scart/db-9 adapter, not with direct philips type cable), not with a PVM using scart cable. Today I luckily acquired an SM124 and image came up fine, so Atari should be ...
by walterg74
Tue Nov 08, 2016 6:42 pm
Forum: Hardware
Topic: Bouncing screen on STF with RGB Scart
Replies: 29
Views: 15684

Re: Bouncing screen on STF with RGB Scart

I had similar issue on a Mega 1 as OP, where the display would jump diagonally by about 1-2cm every few seconds on one TV (Philips LCD) but would be fine on another TV (Sharp LCD). I added a 1N4148 diode and a 10uF capacitor for the BLANKING SCART pin 16 as on your schematic and it solved the issue...
by walterg74
Thu Nov 03, 2016 9:21 pm
Forum: Hardware
Topic: Help with Atari STf - RGB - Cannot get video/sync
Replies: 85
Views: 27381

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

Yes, the SM124 works with separate sync lines, see for example page 9 in the service manual http://dev-docs.atariforge.org/files/SM124_Service_Manual_MT-21.pdf . So the H and V sync lines are fine. (One could of course think of very exotic faults in the GLUE chip that cause H and V sync only to fai...
by walterg74
Thu Nov 03, 2016 6:43 pm
Forum: Hardware
Topic: Help with Atari STf - RGB - Cannot get video/sync
Replies: 85
Views: 27381

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

This is a known Video sync fault.. http://www.exxoshost.co.uk/atari/last/STFMSYNCFIX/index.htm Wait, wasn't this fault only present on STf m machines, and caused by the composite video signal of the modulator? Walter's problem -- if I recall this thread correctly -- was with an STF without modulato...

Go to advanced search