Cub monitor issue

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lordoftime79
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Cub monitor issue

Post by lordoftime79 » Tue Aug 25, 2020 2:59 pm

Hi there, I today have aquired a Microvitec Cub 1431 and it works great with my model B however as I have quite a collection of 8 bit machines I figured I would solder up a scart socket and change the jumpers for non TTL RGB mode however after spendiing about 3 hours messing, rechecking, messing some more I have reached the stage where i am about to give up... I can get my ZX harliquin clone to display but all the white is missing, I can get my Amiga 600 to display but red is so washed out its barely visible (mouse pointer) my BBC B via a RGB scart cable just shows a black screen! what am i doing wrong? I set the jumpers as per the internet I just want some sanity checks? Id love to use this diplay for all these machines as its so sharp and clear!

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danielj
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Re: Cub monitor issue

Post by danielj » Tue Aug 25, 2020 3:13 pm

It will still be expecting TTLish levels even if analogue (i.e. 0-4V I think) IIRC, so if you're feeding it SCART compatible signals then the voltages will be way too low (SCART is 0.7V).

d.

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Re: Cub monitor issue

Post by lordoftime79 » Tue Aug 25, 2020 3:18 pm

ahh ok is there a work around?

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danielj
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Re: Cub monitor issue

Post by danielj » Tue Aug 25, 2020 3:26 pm

Use a straight through cable from the BBC Micro. I have no idea about what comes out of the other systems though - if there are no resistors in-line that can be removed, then they can't be used with it. The one system I know that will work directly in linear mode is the Amstrad CPC.

d.

lordoftime79
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Re: Cub monitor issue

Post by lordoftime79 » Tue Aug 25, 2020 3:44 pm

thats no good for me as i use these devices on a consumer crt and without the resitors i dont think it would display - i wonder if there is a device that can convert analogue RGB to TTL RGB?

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IanS
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Re: Cub monitor issue

Post by IanS » Tue Aug 25, 2020 4:17 pm

I'm curious what the display looks like with white missing, what colour was shown instead? Some pictures may help us understand what is going wrong.

I would have thought setting the cub to analog (0-1v, or 0.7v), so it can work with other machines, and then use a cable with resistors in from the beeb to reduce the ttl levels down to 1V (or thereabouts).

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Re: Cub monitor issue

Post by lordoftime79 » Tue Aug 25, 2020 4:50 pm

118532262_433023891009731_8960495839322855863_n.jpg
118470487_600732620562315_8190581557446591210_n.jpg
118330445_304864127266094_8347183616004233162_n.jpg

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IanS
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Re: Cub monitor issue

Post by IanS » Tue Aug 25, 2020 5:03 pm

Not a lot of RED in that speccy picture, cable all tested?

Have you got the jumpers in the cub set correctly - viewtopic.php?p=257604#p257604

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Re: Cub monitor issue

Post by lordoftime79 » Tue Aug 25, 2020 5:27 pm

cub-pins.PNG
yea cable works fine into my sony crt and phillips crt! the jumpers are set as i found the info.

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danielj
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Re: Cub monitor issue

Post by danielj » Tue Aug 25, 2020 7:18 pm

I don't think CUB on analogue is 0-0.7V.

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Re: Cub monitor issue

Post by lordoftime79 » Wed Aug 26, 2020 1:33 am

so I finally got it working - it was a combination of bad ground and one of the jumpers was wrong but now i have a new issue... the screen is really dark unless i turn up the brightness pot on the pcb but then it looks really washed out and blacks seem grey... any ideas?

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IanS
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Re: Cub monitor issue

Post by IanS » Wed Aug 26, 2020 9:12 am

danielj wrote:
Tue Aug 25, 2020 7:18 pm
I don't think CUB on analogue is 0-0.7V.
You're right, it appears to be 0-4v, which doesn't seem very useful. And woud indeed produce a washed out picture. Why was there all the interest in the analog mode in other threads, what are people using it with?
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cub.PNG

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1024MAK
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Re: Cub monitor issue

Post by 1024MAK » Wed Aug 26, 2020 9:24 am

0.7V (1V pk-pk) is the input level when a composite decoder board is fitted.

In analogue RGB mode an acceptable picture may be possible by adjusting both the brightness and the contrast controls.

I'm mobile at the moment, but if the above does not give you an acceptable picture, there may be some red/green/blue channel level controls (three in total, one per colour channel). It may be possible to adjust these. However, in adjusting these you will be altering the colour balance. And it may not be easy getting a good white unless you are good at preset twiddling...

Mark

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IanS
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Re: Cub monitor issue

Post by IanS » Wed Aug 26, 2020 9:39 am

1024MAK wrote:
Wed Aug 26, 2020 9:24 am
In analogue RGB mode an acceptable picture may be possible by adjusting both the brightness and the contrast controls.
Manual shows the Contrast control doesn't do anything in Analogue mode.

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Re: Cub monitor issue

Post by lordoftime79 » Wed Aug 26, 2020 11:21 am

no only the brighness control :(

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danielj
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Re: Cub monitor issue

Post by danielj » Wed Aug 26, 2020 12:20 pm

It's still the same fundamental problem unfortunately - the monitor is expecting a signal at full brightness to be at 4V, and apart from the beeb (and an Amstrad CPC if you have one), all the machines you're using are providing full brightness at 0.7V. Not a lot doing on that front I'm afraid :(

d.

lordoftime79
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Re: Cub monitor issue

Post by lordoftime79 » Wed Aug 26, 2020 1:20 pm

ok shame that :( guess I still need to source a replacement phillips 8833 mk2 then!

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Re: Cub monitor issue

Post by lordoftime79 » Wed Aug 26, 2020 3:03 pm

So after another hour or so messing - I finally have it decent enough to use :) I had to adjust the the pots on the neck board the gain for all 3 colours needed turning up a little, A right pain as i have big hands so had to turn a little, put it back together test, remove turn a little more, put it back test ect ect - pictures in comming im now giving the metal casing a good clean!

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Re: Cub monitor issue

Post by lordoftime79 » Wed Aug 26, 2020 7:13 pm

118357127_2748029438776594_1669433421267921959_n.jpg
This is how it looks now - still a bit darker than it looks in the Pic but very clear and more than usable!

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1024MAK
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Re: Cub monitor issue

Post by 1024MAK » Wed Aug 26, 2020 8:05 pm

Looks good :D

Mark

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