Dragon 32 jumping to buff mode spontaneously?

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sorchard
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Location: Norwich UK

Re: Dragon 32 jumping to buff mode spontaneously?

Post by sorchard »

Where I've seen colours messed up almost exactly like that before is on the older motherboards that have two variable resistors (pots).

All boards have a pot next to the power connector. This adjusts the video DC level. Older boards have a pot labelled 'RV1' just to the left of the 6847. This adjusts the colour burst phase and directly affects the colours. I remember being surprised to see the colour flipping from green to orange when adjusting it, rather than smoothly changing through a spectrum of colours. Newer boards generate the colour burst in a more reliable way and don't need adjustment.

If the adjustment is marginal then the colours may well vary with fluctuations on the 5V supply. There might be an old capacitor or two slowly reforming and healing which might explain some of what you're seeing.
Stew
moose
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Re: Dragon 32 jumping to buff mode spontaneously?

Post by moose »

Thanks for the hint, I'll take a look. I think this is a rev 2 board, so there's a pot by the power header, but that looks to be the only one. I guess there may be a recap in my future then.

Stu
moose
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Re: Dragon 32 jumping to buff mode spontaneously?

Post by moose »

I'm now somewhat convinced that this is an analogue side issue. I've managed to test the unit on a different screen with built in composite (previously I was using a composite to HDMI adapter). This has stayed 'green' for a good half an hour. My guess is the adapter, being a cheapy, is being a bit more fussy about the composite colour subcarrier. I might still do some recapping in the hope that I can tighten up the signal specs, but I guess the real lesson here is watch out for cheap composite converters.

On a related note does anyone know of a decent CVBS -> HDMI or DVI adapter?

Stu
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unumlapis
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Location: Malmo, Sweden

Re: Dragon 32 jumping to buff mode spontaneously?

Post by unumlapis »

The Dragon composite isn't the best but I would say that a proper converter would be RetroTINK 2X which I hopefully will get myself by the end of this week. I'll primary be using it together with C64 and Amiga; but I'll report how well it goes. Issue here is that the signal output from the Dragon isn't really that good and even if the RetroTINK normally seems to do an outstanding job with C64; it has to be tested.
moose
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Re: Dragon 32 jumping to buff mode spontaneously?

Post by moose »

I'd be interested to see how the Retrotink works out. In the meantime I now have a proper green screen but a couple of annoyances remian. The colours are a little washed out I'm getting some 'bleed through' of the image to the right of the centreas well as occasional very short flickers. Would it be worth fiddling with RV1 and if so are there any dangers?
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unumlapis
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Location: Malmo, Sweden

Re: Dragon 32 jumping to buff mode spontaneously?

Post by unumlapis »

The RetroTINK 2X Pro arrived today for pickup at the local post services and here is some quickly photos taken with Pixel 4 but I'll take some better photos this upcoming weekend and compare with between original CVBS, CoCoVGA and RT2XPro. If there are any suggestions for test images, then let me know and I'll use something as a reference point which we can agree and align around. But, I would say that it does a fairly good job.
Dragon64_RetroTINK2Pro_p01.jpg
Dragon64_RetroTINK2Pro_p01.jpg (2.23 MiB) Viewed 7056 times
Dragon64_RetroTINK2Pro_p02.jpg
Dragon64_RetroTINK2Pro_p02.jpg (1.34 MiB) Viewed 7056 times
sixxie
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Re: Dragon 32 jumping to buff mode spontaneously?

Post by sixxie »

Certainly looks like a thing I would like :)
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unumlapis
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Location: Malmo, Sweden

Re: Dragon 32 jumping to buff mode spontaneously?

Post by unumlapis »

One of the reason why I like the RetroTINK is that the latency is extremely low on this device and pricing is alright if one also compare with the slightly more expense Framemeister which costs around 3x. But, as mentioned, let me take some better picture during this upcoming weekend.
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