new PSUs in my Falcon causes video output to fail

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kodak80
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Re: new PSUs in my Falcon causes video output to fail

Post by kodak80 » Mon May 07, 2018 12:07 pm

I will need to check if the other Falcon has the same clock patch as mine.

My Falcon has the Exxos RTC without the extra capacitor at the moment. The second Falcon has the original NVRAM which needs replacing.

edit: I have added the capacitor to my RTC but it has not solved the boot/video issue.

I have also removed the RTC and inserted Dallas RTC to test things. Again, no difference to the boot/video.
Atari Falcon 030 | Atari 1040 STE | Atari 1040 STFM | Atari 1040 STF | Kryoflux & Supercard Pro Flux boards
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Re: new PSUs in my Falcon causes video output to fail

Post by exxos » Mon May 07, 2018 2:35 pm

I would add the resistors on the clock patch is the only thing I can think of currently.
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

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kodak80
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Re: new PSUs in my Falcon causes video output to fail

Post by kodak80 » Wed May 30, 2018 12:00 pm

I have now replaced the original clock patch with an Exxos clock patch to see if this would solve my issues. It did not. Issue still exists with new PSUs. I also now have 3 original Falcon PSUs which all work and boot my Falcon fine.

I am looking to do some more diagnostics with an Atari friend who is also an electrician this weekend.
Atari Falcon 030 | Atari 1040 STE | Atari 1040 STFM | Atari 1040 STF | Kryoflux & Supercard Pro Flux boards
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kodak80
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Re: new PSUs in my Falcon causes video output to fail

Post by kodak80 » Sat Jun 09, 2018 1:03 pm

OK, after some more investiagtion, we have identified causes and solved things so my Falcon now boots. :)

There were 2 issues:
1. My Exxos PSUs are not outputting full 5v - only 4.96v which is borderline for booting my Falcon. We confirmed that 4.94v is not enough to boot my Falcon.
2. My Exxos PSUs have around a 20-24ms delay in delivering full 5v rail when powered on. Original Falcon PSU delay is 2-4ms. C7 capacitor was 1uf and delay on commencing reset was not long enough for new PSU and 20-24ms delay meant 5v was not ready on the Falcon.

Solution:
1. replaced my Falcon C7 capacitor with 3.3uf capacitor to allow for new PSU 5v deleivery delay of 20-24ms.
2. PSU was modified by adding two resistors 1.2k and 24ohm voltage divider to feed pin 4 at LM2576T regulator to allow the PSU to provide 5.1v so that power supplied was no longer borderline.
My Falcon now powers on 1st time and boots with the above changes. The original PSU also still works.
Atari Falcon 030 | Atari 1040 STE | Atari 1040 STFM | Atari 1040 STF | Kryoflux & Supercard Pro Flux boards
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Re: new PSUs in my Falcon causes video output to fail

Post by exxos » Sat Jun 09, 2018 2:25 pm

Interesting. I will try running my falcon from my bench PSU at lower voltages when I get chance to see if I can replicate the issue.
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

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Re: new PSUs in my Falcon causes video output to fail

Post by exxos » Fri Jun 22, 2018 3:52 pm

kodak80 wrote:
Sat Jun 09, 2018 1:03 pm
We confirmed that 4.94v is not enough to boot my Falcon.

I did a quick experiment on this with a hacky SR98 as could easily alter the 5V levels...


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

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mikro
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Re: new PSUs in my Falcon causes video output to fail

Post by mikro » Thu Jul 12, 2018 10:12 pm

My two cents of experience -- couldn't observe this behaviour at all. Rob's Falcon indeed must be a very special one. :) My 5V line was even worse, I'd measured about 4.84V there.

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Re: new PSUs in my Falcon causes video output to fail

Post by mikro » Wed Aug 22, 2018 7:40 pm

mikro wrote:
Thu Jul 12, 2018 10:12 pm
My two cents of experience -- couldn't observe this behaviour at all. Rob's Falcon indeed must be a very special one. :) My 5V line was even worse, I'd measured about 4.84V there.
Ha-ha-ha. Do you know that expression about not saying something prematurely? Guess what - some time ago I have noticed that my CT2 Falcon with Exxos PSU doesn't boot on the first time anymore. I'm not seeing the stars as Rob did, just out of scan range and that's it. Pushing the reset button solves the problem.

I also happen to know this can be related to bad clock patch as I had an issue like this before with my PowerUp2'ed Falcon but not this time -- the CT2 has a top-notch clock patch. And what's the most important thing - it works with the original PSU, both "original original" and a recapped one. Unfortunately for a world I can't remember whether I was using Exxos PSU with this Falcon before or just the recapped one.

Funnily, I even have a Centuriontech PSU ready for test but I haven't forced myself to change the original PSU yet (what, according to Rob's experience above, wouldn't help me anyway and I'd loose my only 100% working PSU for that Falcon).

So I'm going to try Rob's / Paul's fixes and report back.

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Re: new PSUs in my Falcon causes video output to fail

Post by mikro » Wed Aug 22, 2018 8:49 pm

Phew, solved. Before trying more exotic approaches I remembered the classic fix by Rodolphe Czuba for the CT60 with various ATX PSUs: http://powerphenix.com/ct60/english/fitting63.htm (bottom)

So I've just added a 22uF capacitor to C7:
IMG_20180822_213731.jpg
IMG_20180822_213731.jpg (1.13 MiB) Viewed 185 times
and voila! I really hope it's not going to 'revert' like Rob mentions here: viewtopic.php?f=23&t=755#p5446 (btw why did you put that 22 uF capacitor there and not on C7?).

BTW: I didn't have any axial capacitors at home and I did have this radial one from Brisbane so I used that. Yes, this little fellow travelled about 20 000 kms only to be installed in Europe. :)

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Re: new PSUs in my Falcon causes video output to fail

Post by exxos » Wed Aug 22, 2018 9:40 pm

Was that the reset cap ? I'm seeing those problems on some STE's where one cap doesn't seem to do anything anymore.
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.

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