Evening all.
So, I have been away from the 600D build for a bit, since it was getting super frustrating.
In the meantime I built an Altairduino and uKENBAK-1 from adwaterandstir:
And it's got me in the right frame of mind to get going on the 600D again.
Given that I know 'something' is happening and I can see what looks like pixels on my micro B&W tv, I think I need to start going through the video circuit with a fine toothcomb.
I know I am getting what looks to be a good video signal, and I know that it's not a PAL/NTSC issue since my Dell display will do either and using an NTSC -> PAL adapter didn't help either.
So I am going to identify all the IC's from the video circuit and do some close up checking for bent pins and then check all the power/gnd pins and all the signals going in, as though I have the main clock fixed, I can't help but think that if a clock signal of any sort going into the video circuit is off, then I just won't get a proper signal coming out.
The lack of a back porch in the video signal does bother me too, so if anyone out there with an oscilloscope and a Klyball 600D could provide a picture of their video signal for reference it would be a huge help.
Thanks.
My Klyball 600D build
- jbtech
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Re: My Klyball 600D build
Hi, here are a couple of CRO images from mine, not terminated so output level is over 2V but the timing should be correct:
Video lines: there is a front and back porch and sync looks correct at about 5us
Video frame, I just held a key to fill the screen with characters so the last line with characters is the cursor position
Vertical interval expanded
Hope that helps, regards John.
Video lines: there is a front and back porch and sync looks correct at about 5us
Video frame, I just held a key to fill the screen with characters so the last line with characters is the cursor position
Vertical interval expanded
Hope that helps, regards John.
More from John's Retro Workshop http://www.jbtech.linkpc.net
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Re: My Klyball 600D build
Thanks so much!!jbtech wrote: ↑Tue Mar 19, 2024 3:25 am Hi, here are a couple of CRO images from mine, not terminated so output level is over 2V but the timing should be correct:
Video lines: there is a front and back porch and sync looks correct at about 5us
IMG_2133.JPG
Video frame, I just held a key to fill the screen with characters so the last line with characters is the cursor position
IMG_2136.JPG
Vertical interval expanded
IMG_2139.JPG
Hope that helps, regards John.
My video signal, though at the correct frequency, I don't seem to have either a front or back porch, so that's again suggesting an issue with something in the video circuit, as I can see pixels in the rolling image, but it's clearly got a problem with vertical sync as I can see the horizontal is fine on my scope.
I'll get checking the ICs that form the video circuit and any clocks that need to be present.
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Re: My Klyball 600D build
OK, so some progress. By removing U61 I was able to get this:
Which didn't make sense until I realised that the HSYNC clock, 15.63Mhz is derived from U60, but the VSYNC is derived from U61.
Checking U61 I found that the C15 signal (60Hz) used for VSYNC originates at U61 and does arrive at U65 pin 1 and VSYNC should come out of pin 4, so I lifted that pin and got the same result as pulling U61.
Since U61 feeds 60Hz to U65, I was expecting to see a VSYNC signal of 60Hz at pin 4, but instead I see 15.63Khz again.
Surely I should see both 60Hz and 15.63Khz separately at U65 pins 4 & 12 respectively, and also at pins 12 & 13 of U70? I just see 15.63Khz at both.
I have checked for shorts between pin 4 & 12 but they are fine.
Any ideas welcomed
Which didn't make sense until I realised that the HSYNC clock, 15.63Mhz is derived from U60, but the VSYNC is derived from U61.
Checking U61 I found that the C15 signal (60Hz) used for VSYNC originates at U61 and does arrive at U65 pin 1 and VSYNC should come out of pin 4, so I lifted that pin and got the same result as pulling U61.
Since U61 feeds 60Hz to U65, I was expecting to see a VSYNC signal of 60Hz at pin 4, but instead I see 15.63Khz again.
Surely I should see both 60Hz and 15.63Khz separately at U65 pins 4 & 12 respectively, and also at pins 12 & 13 of U70? I just see 15.63Khz at both.
I have checked for shorts between pin 4 & 12 but they are fine.
Any ideas welcomed
- jbtech
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Re: My Klyball 600D build
So, if you have 15kHz at pin 4 of U65 but you're sure /HS and /VS aren't shorted together and the input at pin 1 of U65 is correct at 60Hz -
check for other possible interaction e.g. pins 2 and 3, 10 and 11 should be held high, make sure they are not toggling at 15kHz due to a shorted track etc.
Likewise make sure the +5V and ground to the IC are correct and not floating or carrying noise.
Failing that try replacing the IC! Good luck, regards John.
check for other possible interaction e.g. pins 2 and 3, 10 and 11 should be held high, make sure they are not toggling at 15kHz due to a shorted track etc.
Likewise make sure the +5V and ground to the IC are correct and not floating or carrying noise.
Failing that try replacing the IC! Good luck, regards John.
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Re: My Klyball 600D build
what happening at pin 8 u43
Replica 600 Rev D:8K,CEGMON
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510 on the bench/replica 582 backplane/replica 470a /replica 555/original 570B/2 x Shugart 851
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Replica 610 Rev B: 24k,MPI B-51 with Custom Data separator D-13
510 on the bench/replica 582 backplane/replica 470a /replica 555/original 570B/2 x Shugart 851
Ongoing : 630 ,620 ,510,542c,custom 590,SA1200,592,594,596,598
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Re: My Klyball 600D build
OK, I have figured out what was wrong video wise and now have a working video circuit
So U65 was getting 60Hz at pin 1 but throwing out 15.65Khz on pin 4. The only way this could have been an issue is if the LS123 was faulty, which I knew it wasn't (I'd tested it), so that just left C8 and R3 which is the external capacitor/resistor combo controlling the part of U65 that creates VSYNC.
R33 was unlikely to be wrong or faulty, I mean it's just a resistor, and that was all good.
However it turned out I had C8 in the wrong holes as I misinterpreted a diagram I was given that looked like this:
I used the hole marked in red for C8 as I though it was highlighting it should go there, when in actual fact I should have used the holes either side of the red mark.
With it correctly located:
I now get this on-screen with no CPU fitted:
Which I think proves the CHARGEN and video RAM is working.
Sadly with the CPU fitted I see this:
And that's with or without ROMs installed, so there is something else to investigate as I'm guessing that's a crash of some sort.
BTW pressing break does cause a reset signal at the CPU and the screen twitches, but goes no further and doesn't change.
Currently I only have 2 RAM ICs installed and the 2 for video RAM. I do have the remaining RAM ICs so might just swap the 2 out.
At least now I have a clear video image to work with for the next steps of troubleshooting, and as always, any tips welcomed
So U65 was getting 60Hz at pin 1 but throwing out 15.65Khz on pin 4. The only way this could have been an issue is if the LS123 was faulty, which I knew it wasn't (I'd tested it), so that just left C8 and R3 which is the external capacitor/resistor combo controlling the part of U65 that creates VSYNC.
R33 was unlikely to be wrong or faulty, I mean it's just a resistor, and that was all good.
However it turned out I had C8 in the wrong holes as I misinterpreted a diagram I was given that looked like this:
I used the hole marked in red for C8 as I though it was highlighting it should go there, when in actual fact I should have used the holes either side of the red mark.
With it correctly located:
I now get this on-screen with no CPU fitted:
Which I think proves the CHARGEN and video RAM is working.
Sadly with the CPU fitted I see this:
And that's with or without ROMs installed, so there is something else to investigate as I'm guessing that's a crash of some sort.
BTW pressing break does cause a reset signal at the CPU and the screen twitches, but goes no further and doesn't change.
Currently I only have 2 RAM ICs installed and the 2 for video RAM. I do have the remaining RAM ICs so might just swap the 2 out.
At least now I have a clear video image to work with for the next steps of troubleshooting, and as always, any tips welcomed
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Re: My Klyball 600D build
See "What happens to my C1P upon RESET?" @ viewtopic.php?p=4500#p4500
Are you getting ACIA access after RESET? Um... U14 6850 Pin 9 / U17 'LS139 Pin 12? If so then check for bad low 1K RAM U31/U45 as the screen won't clear if the stack doesn't work. D/C/W/M? display depends on BASIC ROMS.
Good Luck!
Are you getting ACIA access after RESET? Um... U14 6850 Pin 9 / U17 'LS139 Pin 12? If so then check for bad low 1K RAM U31/U45 as the screen won't clear if the stack doesn't work. D/C/W/M? display depends on BASIC ROMS.
Good Luck!
- jbtech
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Re: My Klyball 600D build
Hi, I'm not sure offhand if I mentioned this before but looking at one of your earlier photos - if you only have 2 RAM ICs fitted (plus the video RAM) make sure they are the pair nearest the edge of the PCB, not nearest the middle.
- Just in case... Regards, John
- Just in case... Regards, John
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Re: My Klyball 600D build
Thanks John, I didn't realise that, I will swap them around.jbtech wrote: ↑Wed Mar 20, 2024 6:04 am Hi, I'm not sure offhand if I mentioned this before but looking at one of your earlier photos - if you only have 2 RAM ICs fitted (plus the video RAM) make sure they are the pair nearest the edge of the PCB, not nearest the middle.
- Just in case... Regards, John