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Cromemco dazzler replica project

The color carrier is in the output signal and blue is fine. The other colors probably are too , you could check those in a similar manner. You could try running K scope or the Dazzler demo again now on the apple monitor.
 
Well done Dave, another well diagnosed process.

So

In a nutshell, the boards work but you need the right type of RAM, static & non buffered

and the right monitor.

Really satisfying that it works.
 
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Looking at the photo of the other VDU, where the the image appeared as stripes, I think you are seeing the blue color carrier interpreted by the VDU as a luminance signal, as it goes fairly close to black level on the negative peaks of the blue carrier, and zooming up the three phosphor dots are lit in the part of the cycle where the carrier peaks, where it should only be the blue one lit, so I think in that VDU, the color killer must have activated and that VDU is in monochrome mode.

Its all good news with the apple VDU.
 
>>> Yeah, I guess I hadn't tried this monitor since we got the RAM issue sorted..

I think we had a few different things going on. The RAM issue would have given us a 'solid' screen no matter what we did. If we had D6=1 (X4 resolution) and D4=1 (colour mode) then we should have got some colour out of it by playing with the lower four bits - but only if we had the variable capacitor and the two colour potentiometers tweaked correctly.

>>> Well done Dave, another well diagnosed process.

The only thing that was really wrong (in the end) was the RAM card issue - which was a bit mean...

>>> In a nutshell, the boards work but you need the right type of RAM, static & non buffered

A non-latched address bus was the key thing in the end. Some latched address bus cards may still work though, depending if they include a PHI2 clock.

DRAM seems to be a problem because of the refresh (or rather lack of) - but I wonder if that is true anymore with faster DRAM devices?

Dave
 
daver2 said:
>>> Yeah, I guess I hadn't tried this monitor since we got the RAM issue sorted..

I think we had a few different things going on. The RAM issue would have given us a 'solid' screen no matter what we did. If we had D6=1 (X4 resolution) and D4=1 (colour mode) then we should have got some colour out of it by playing with the lower four bits - but only if we had the variable capacitor and the two colour potentiometers tweaked correctly.

>>> Well done Dave, another well diagnosed process.

The only thing that was really wrong (in the end) was the RAM card issue - which was a bit mean...

>>> In a nutshell, the boards work but you need the right type of RAM, static & non buffered

A non-latched address bus was the key thing in the end. Some latched address bus cards may still work though, depending if they include a PHI2 clock.

DRAM seems to be a problem because of the refresh (or rather lack of) - but I wonder if that is true anymore with faster DRAM devices?

Dave
Click to expand...
Given the note in the Northstar manual about using their Dynamic RAM with the Dazzler after a modification then I might have a go at building one now for myself and see if it works.
 
Wow colors look much better after going through the whole tuning process.. Yellow and Cyan still seem 'off' to me but the rest of the colors look pretty good.

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nullvalue said:
Well hold on now I just plugged it into my AppleColor monitor and the picture is actually blue!
Click to expand...

Sanity check for you: When you had this plugged into the Commodore 1701 were you using the jack on the back or the one on the front?

The jacks on the *back* of the 1701 are separated Luma/Chroma inputs; if you plug a composite signal into the Luma input it will "work", but only in monochrome. Those two jacks together are essentially the same as the "S-Video" plug you find on a lot of 90's-2000's TVs, DVD players, and more expensive VCRs.

If you weren't before, try it in the front jack.
 
Hugo Holden said:
The K scope seems like it is running faster than in my SOL, have you gone back to the 4MHz clock ?
Click to expand...

I did yep, just as an experiment yesterday but I've left it there. GDEMO looks really good at 4MHz, but yeah I think KSCOPE looks better at 2MHz
 
@Hugo Holden ah, I see in your post #24 you made the same notes about yellow & cyan looking desaturated. I guess that's just how it is. :)
 
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Figured I'd try to do it justice and record a decent video with my DSLR.. here's GDEMO running @ 4MHz:

 
Thanks again everyone your help getting this set working -- especially Hugo, Gary & Dave! It's been really fun & educational putting this together. Will be cool to see what kind of software we can come up for these. BTW I have 4 sets of the PCBs if anyone wants, just will need the simple mods we performed on them. ENIG but not hard gold or anything fancy. $25 for the set shipped in the US.
 
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nullvalue said:
Good thought, but nope I've been using the front jack this whole time.
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Weird. I have to guess the Apple monitor is just more tolerant about something being a little off with either the frequency or amplitude of the color signals? (When you consider how off-spec the color signals coming out of Apple IIs are its not crazy to think the company might have specifically tried to make their monitors more forgiving...) But congratulations on getting colors out of it!
 
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