STE video synchronisation problem

Problems with your machine in general.
Number_Nine
Posts: 21
Joined: Tue Sep 19, 2017 1:48 pm
Location: UK

STE video synchronisation problem

Post by Number_Nine » Sat Sep 23, 2017 8:43 pm

Hi there,
I got a PAL Atari 1040STE which has video sync problem, so I've been debugging it today and noticed that VSync and HSync are all right, but CCLK signal is suspiciously silent (both video connector pin #2 and U403 MC1377P pin 17).
According to MC1377 sheet it should be around 2-3 MHz, but on my machine it's just 4V all the time.
I've been scrolling through STE schematics many hours today and still I can't see where it comes from.
Clipboard02.jpg
Clipboard02.jpg (35.48 KiB) Viewed 522 times
I would imagine it comes either from MCU or maybe Shifter, or something like VSync gets mixed with HSync...
Any idea, please?

PS: Poked PSU with a scope - not much noise, levels seem OK too. Dully recapped C103, C415, C417, C423, C433.

User avatar
rpineau
Posts: 261
Joined: Thu Aug 17, 2017 6:08 pm
Location: USA
Contact:

Re: STE video synchronisation problem

Post by rpineau » Sat Sep 23, 2017 11:47 pm

CCLK goes U308B pin 12 and comes from a clock circuit only present on PAL machines (I put the signal in red bellow) :
Screen Shot 2017-09-23 at 15.45.00.png
Screen Shot 2017-09-23 at 15.45.00.png (664.39 KiB) Viewed 510 times
Rodolphe

User avatar
exxos
Site Admin
Posts: 2211
Joined: Wed Aug 16, 2017 11:19 pm
Location: UK
Contact:

Re: STE video synchronisation problem

Post by exxos » Sun Sep 24, 2017 12:11 am

Some monitors do not like st video modes.

You could try this fix where a couple people said it helped with sync issues also.

viewtopic.php?f=17&t=135
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
https://www.exxoshost.co.uk/atari/last/storenew/ - All my hardware mods for sale - Please help support by making a purchase.

Number_Nine
Posts: 21
Joined: Tue Sep 19, 2017 1:48 pm
Location: UK

Re: STE video synchronisation problem

Post by Number_Nine » Sun Sep 24, 2017 10:48 am

rpineau wrote:
Sat Sep 23, 2017 11:47 pm
CCLK goes U308B pin 12 and comes from a clock circuit only present on PAL machines (I put the signal in red bellow) :
Screen Shot 2017-09-23 at 15.45.00.png

Rodolphe
Much appreciated!

Number_Nine
Posts: 21
Joined: Tue Sep 19, 2017 1:48 pm
Location: UK

Re: STE video synchronisation problem

Post by Number_Nine » Sun Sep 24, 2017 10:49 am

exxos wrote:
Sun Sep 24, 2017 12:11 am
Some monitors do not like st video modes.

You could try this fix where a couple people said it helped with sync issues also.

viewtopic.php?f=17&t=135
I am using an old CRT Philips CM 8802 which works perfectly with my other STE.
Thanks for the link, I think that might be a bit different, but I'll try your fixes.

User avatar
exxos
Site Admin
Posts: 2211
Joined: Wed Aug 16, 2017 11:19 pm
Location: UK
Contact:

Re: STE video synchronisation problem

Post by exxos » Sun Sep 24, 2017 11:02 am

Number_Nine wrote:
Sun Sep 24, 2017 10:49 am
I am using an old CRT Philips CM 8802 which works perfectly with my other STE.
Thanks for the link, I think that might be a bit different, but I'll try your fixes.
Its easy to try, not exactly the same no, but its the regulator for the video circuit. So its a sensible place to start :)
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
https://www.exxoshost.co.uk/atari/last/storenew/ - All my hardware mods for sale - Please help support by making a purchase.

Number_Nine
Posts: 21
Joined: Tue Sep 19, 2017 1:48 pm
Location: UK

Re: STE video synchronisation problem

Post by Number_Nine » Sat Sep 30, 2017 6:20 pm

Having changed U403 (MC1377P), still no idea why is there nothing (constant 6VDC) on the composite output (pin 9 of U403), still guessing it might be because something is wrong with the Osc In signal (pin 17) - I see CCLK on R469, but after R469 it's so weak so after C 427 U403 has +5V instead of CCLK on its own (I've tried 4 MC1377Ps - all the same, I have to check this pin on a good Atari, though), but bypassing composite sync to composite output seems to work for me, as anyway I am getting RGB right from U401, but yes modulator won't work like this...
DK_HqnDXcAAWuXe.jpg
DK_HqnDXcAAWuXe.jpg (198.95 KiB) Viewed 463 times
DK_HqnCW0AAMgd5.jpg
DK_HqnCW0AAMgd5.jpg (130.47 KiB) Viewed 463 times

Number_Nine
Posts: 21
Joined: Tue Sep 19, 2017 1:48 pm
Location: UK

Re: STE video synchronisation problem

Post by Number_Nine » Sat Sep 30, 2017 9:31 pm

Checked a working Atari STE - everything is just exactly the same, the only difference is that it has also composite out on pin 9.
I am out of ideas.

User avatar
exxos
Site Admin
Posts: 2211
Joined: Wed Aug 16, 2017 11:19 pm
Location: UK
Contact:

Re: STE video synchronisation problem

Post by exxos » Sun Oct 01, 2017 12:41 am

Number_Nine wrote:
Sat Sep 30, 2017 9:31 pm
Checked a working Atari STE - everything is just exactly the same, the only difference is that it has also composite out on pin 9.
I am out of ideas.

What are you seeing on cclk on working and none working machines ? Can you post scope images?

Have you lifted pin 9 out of the socket and checked that way ?

What is on pin 2 of the 1377 ?

Check q404 and make sure you have 12v there.
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
https://www.exxoshost.co.uk/atari/last/storenew/ - All my hardware mods for sale - Please help support by making a purchase.

Number_Nine
Posts: 21
Joined: Tue Sep 19, 2017 1:48 pm
Location: UK

Re: STE video synchronisation problem

Post by Number_Nine » Sun Oct 01, 2017 2:21 pm

exxos wrote:
Sun Oct 01, 2017 12:41 am
Number_Nine wrote:
Sat Sep 30, 2017 9:31 pm
Checked a working Atari STE - everything is just exactly the same, the only difference is that it has also composite out on pin 9.
I am out of ideas.

What are you seeing on cclk on working and none working machines ? Can you post scope images?

Have you lifted pin 9 out of the socket and checked that way ?

What is on pin 2 of the 1377 ?

Check q404 and make sure you have 12v there.
Thanks for the reply.

I have already assembled the good Atari back together as I noticed no differences earlier.

12V on collector of Q404 is there.
With pin 9 of 1377 unconnected - all the same (no Composite off it).

CCLK:
SDS00001.jpg
SDS00001.jpg (29.75 KiB) Viewed 430 times
Pin 2 of 1377 (VSync + HSync -> XOR (U2009A) -> Invertor (U211C)):
SDS00003.jpg
SDS00003.jpg (28.07 KiB) Viewed 430 times
Pin 17 (Osc In) on 1377:
SDS00002.jpg
SDS00002.jpg (26.33 KiB) Viewed 430 times

Post Reply