My Klyball 600D build

[ronin47]

So, the clock circuit is definitely saying no.

I have 4 Mhz at pin 5 of U79 and pin 4 is connected to ground, but there is no output at all on pin 6, so by connection, none at pin 9, so I only ever get 4Mhz out at pin 8, the same at pin 1 of U29, and of course then I just get 500KHz out at pin 11 of U29.

I've tried swapping U58 (7400, 74S00 & 74LS00), U79 (74LS86) and U29 (74LS93). All the removed chips test just fine in my TL866 Pro.

I've also swapped out C57 and C65, and those parts also tested fine. Last night I also removed the sockets for U58 and U79 to check for shorts underneath, despite everything buzzing out OK. No difference with new sockets in.

No matter what I do, it flatly refuses to deliver 8Mhz from the LS86.

I have just received an 8MHz xtal, so I am going to try and switch the clock circuit to that of the 600's UK sibling, the UK-101, which dispenses with the clock doubling trickery of U79 and uses an 8MHz clock going straight to U29.

I'll report back when I've had the chance to test this out.

[ronin47]

Feeling a bit dumb, turns out I had a 150nF cap in at C65, not 150pF. Not sure how it happened, but removing it has made the clocks work properly, though the machine isn't showing any video yet I can at least start to troubleshoot.

Arrrrgggghhhh!

[ronin47]

So, my clocks are working now, but I still have no video when I attempt to run test 5.

I have scoped my video out (Blue trace), and this is what I get:

PXL_20240203_115842604.jpg (1.62 MiB) Viewed 929 times

Yes, the yellow trace is the CPU clock

And if I adjust the pot at R57, I can see the signal is being mixed as I would expect at the video out. Before I fixed the clock, I didn't get any mixing of the video and sync pulses.

The question is now, is that it doesn't seem to have a backporch like my TRS-80 Model 1 shown here (Yellow trace):

PXL_20240203_131556524.jpg (1.76 MiB) Viewed 929 times

So is it supposed to have a backporch, and if not will it struggle to display anything on my LCD display with composite in?

Thanks.

[Klyball]

Some lcd monitors could struggle your signal looks good

[ronin47]

Some lcd monitors could struggle your signal looks good

Thanks, it's good to know that the signal looks right.

I've got an older black and white TV coming that has composite in, and in the meantime I'll see if any of my other displays will pick it up.

[waltermixxx]

How are you making out with the REV D?

did you get up and running? perhaps we can do a facebook or facetime call and compare notes? your last post with clock and video look good.
when you hit BREAK (for a few seconds) does the video signal change at all? I'm not sure I will be much help, but willing to try?

I built 2 of these REV D's one for me, and one for Steve Gray, he's a big OSI guy so to speak I'm currently building my 502, 540B, 542, and back plane based system.

Cheers.

[ronin47]

How are you making out with the REV D?

did you get up and running? perhaps we can do a facebook or facetime call and compare notes? your last post with clock and video look good.
when you hit BREAK (for a few seconds) does the video signal change at all? I'm not sure I will be much help, but willing to try?

I built 2 of these REV D's one for me, and one for Steve Gray, he's a big OSI guy so to speak I'm currently building my 502, 540B, 542, and back plane based system.

Cheers.

Hey there @waltermixxx, thanks for pinging this to me, and I appreciate the offer of help.

A couple of things. I got a bit fed up with it, so stepped away from it, and then got distracted by a Sharp MZ-700, CBM128 and a TRS-80 Coco!!!

I guess that's more than a couple of things

The Sharp and TRS are in the fixed pile, and I'm waiting on parts for the C128, but it's taken me away from the 600D.

So, whilst the video signal looks fine on my oscilloscope, I can't get an output on my composite display, which I know works as I use it for a bunch of other stuff.

I have tried my usual TV, it's an LCD, so I am kind of not surprised it doesn't work on that, my Retrotink 2 and my Dell LCD display that works fine with my TRS-80 Model 1 and my Apple IIe.

I occasionally get some sort of signal picked up by the Dell, but it's off and on.

Hitting break, I can see the change in reset signal at the CPU, so that's good, and also I can see the video signal change when I hit break as well, suggesting it's doing something.

I also have a small B&W portable TV now with a composite input and I get this:

PXL_20240207_221000752~2.jpg (550.15 KiB) Viewed 344 times

It does look like something is on the display.

Now I live in the UK and I'm wondering if I have a 50Hz/60Hz issue here, but I don't know 100%.

I can't help but think if I am getting a good signal, and turning R58 does change the video output so things are getting mixed there ok now the clocks are fixed, that there is still a problem with the video circuit I haven't found, either that or I don't seem to have any displays that will work with the 600D signal.

The chap I got the board from is also I think in the UK, so the 50Hz/60Hz thing seems like it isn't going to be a problem, as his works fine, so I am wondering if I have a bad part in the video circuit or a solder bridge similar to what happened with him.

I am going to get back to it soon, and I think I need to focus on the video circuit next.

[Klyball]

im not a expert on the signal but it could be a pal/ntsc issue. im comparing the 2 schematics uk101 to the 600 it looks like there doing the timing for hs and vs a bit different.

[ronin47]

im not a expert on the signal but it could be a pal/ntsc issue. im comparing the 2 schematics uk101 to the 600 it looks like there doing the timing for hs and vs a bit different.

Hmm, interesting. I presume then that the guy I got the board from has a display that can do either PAL or NSTC, now wondering how I'm going to get this thing to display at all.

I don't know a lot about the video signals, but I didn't realise that composite could be PAL or NTSC. Clearly I got that wrong having just read this: https://en.wikipedia.org/wiki/Composite ... rrelevant.

So I've managed to find an NTSC to PAL converter on Amazon so I've ordered one to see if it helps me out at all. It is switchable too, so will also do PAL to NTSC.

Should arrive Saturday, so lets keep fingers crossed!!!

[ronin47]

Not had much time to work on this over the weekend as I've been working on a C128 and TRS-80 Coco 1.

So a small update. The PAL <=> NTSC adapter (It does both directions) arrived and I set it up in NTSC to PAL mode, but still no image out of the 600

Now I think that it is displaying something based on what I can see on the small black and white TV, but feeding it into the adapter gave me nothing at all.

What I was able to do is verify, using the adapter, is that my LCD will accept both PAL and NTSC signals, so overall it has to be the signal that's the problem, so I will start working through the video circuit to try and figure out what's going on.

Although the video signal looks OK, it is clearly wrong in some way, so I need to focus on that right now.

It's proving a challenging build!