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DEC Rainbow 100 with video glitch

B

Bavarese

Member
Joined
Apr 18, 2013
Messages
10
Location
Germany
Hi,

my Rainbow 100-B has a video glitch and started to display ERROR 1 (VIDEO), later ERROR 10 (VIDEO VFR - possibly related to the 60 HZ vertical blank interrupt?).

Things changed after i reseated all socketed chips - now i get ERROR 2 (unsolicited interrupt) and get a boot screen (see screenshot below).

I hope someone can give me a hint what is broken -

Screenshot of the video glitch (how it looks now):
https://dl.dropboxusercontent.com/u/37819653/ERROR_1_10_VIDEO_VFR.jpg

How the boot screen * should * look
https://dl.dropboxusercontent.com/u/37819653/Rainbow_100_Logo_BW.jpg
(taken from an internal beta driver for the MESS emulator) :)

Of course, if already searched the forums and found this interesting thread
http://www.vintage-computer.com/vcf...lems-with-DEC-VT100-Terminal&highlight=repair

From what i heard, the Rainbow shares components with the VT-1xx series (it has the same DC011 and DC012 chips inside).

Maybe the problem i have is related...?

Thanks for any info,
Carl
Location: Germany
Some experience with soldering. Access to analogue 20 Mhz Scope and an 8 channel "Salae" (USB) Logic Analyser.
 
Carl,

The Rainbow's basic video section is indeed like the VT100. I have seen something like this in a VT100, but I can't remember exactly the problem. It could very well be the character generator rom since at first glance there seems to be some stuck bits (number 0 prints out correctly, but number 1 also prints out like number 0.) I see something with small letters s, r, and t printing out like 2, 3, and 4 which differ in ASCII code by only one bit. Perhaps the chargen rom or some logic that drives it is sick, just like in the old thread you mentioned. The chargen rom may be socketed, so burn another one and try it.

Lou
 
Last edited:
Hi Carl,

I too have a Rainbow with screen troubles. Sadly I don't think mine is close enough to yours to be of much help. I get corrupt vertical areas down the screen in which attributes are set. If I get anywhere I'll let you know.

All the best,

Andy.
 
Hi Lou,

Thanks for that. Always welcome :)

I'm still finding my feet with the Rainbow. I came to a halt on the PDP-11/53 for a while, waiting for a cable so I dusted off the Rainbow to fill in. I'll look over the schematics and find the RAM as suggested.


Thanks,

Andy.

Lou - N2MIY said:
Andy,

The rainbow has separate character attribute ram similar to the AVO in the VT100. Find the bad ram and replace it.

Lou
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