Lambda colour kit

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1024MAK
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Re: Lambda colour kit

Post by 1024MAK » Tue Oct 08, 2013 1:05 pm

sirmorris wrote:The unit can be switched to NTSC using a jumper on the board. I can't tell you what it is off the top of my head but I'm sure someone will be along any second to fill in the details 8-)
This refers to a wire link on the ZX81 PCB. This changes the timing used by the video generation system so that it works on a 60Hz EIA 525/60 system.

Which composite mod did you do. Some give better results than others depending on the TV.
Older CRT type TV's are generally more tolerant of the non-standard Zeddy video signal.
Some TV's do not like the DC voltage on the video signal that the modified Zeddy produces. In this case add a 100uF 16V electrolytic capacitor in series between the composite video output from the ZX81 and the lead to the TV.

Also note that the ZX81 does not generate a PAL signal, as it does not produce colour!
PAL is a colour encoding system. The signal that the ZX81 produces is a monochrome 625-line 50Hz video signal defined as CCIR 625/50. The UK broadcast system is known as "CCIR system I" (letter I NOT number 1). This is an interlaced video signal with a frame rate of 25Hz, a field rate of 50Hz, a horizontal frequency/line rate of 15625Hz (or 15.625kHz) and a video band-width of 5.5 MHz. When colour information is combined to this, it is often called PAL I.

If you want to know more about the 525/60 link, shout out ;)

Mark

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TMAOne
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Re: Lambda colour kit

Post by TMAOne » Wed Oct 09, 2013 2:06 am

1024MAK wrote:This refers to a wire link on the ZX81 PCB. This changes the timing used by the video generation system so that it works on a 60Hz EIA 525/60 system.
I hope there is a also a link on the Lambda color module as originally suggested. I have just obtained a European module, and am in Canada, and so far have not been able to make it work, with either the RF or the monitor output. My color TV's don't much like the stock Lambda either--the only video I have working well is an early 80's vintage black and white TV, which is hardly the ticket for color work.

I haven't tried the module on a ZX81, and am not sure if I dare to do that experiment. The color module is expecting inverse video. Would that be a problem 1024MAK?

By way of apology for jumping into the thread, I offer scans of the color module instruction insert. :)

Ian
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pemilsson
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Re: Lambda colour kit

Post by pemilsson » Thu Oct 10, 2013 4:11 am

Thanks for all the info, this is really a great forum :)

Right now I'm focusing on getting my Swedish ZX81 work with my fairly new American Toshiba LED TV and it seems to be a challenge.
I have made the video conversion described here viewtopic.php?f=7&t=1125&start=10
I added a zero ohm jumper at R30 to get the 60Hz
I have tried to send my video signal through my home video amplifier in a hope that it might adjust the signal.

Unfortunately none of the above have convinced my TV to show anything.

I now also done some measurements to verify that the signals looks good.
Could it be that I don't have correct 0 ref in the signal?
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zx81 after home movie receiver.png
zx81 after home movie receiver.png (60.14 KiB) Viewed 621 times
ZX81 complete picture.png
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zx81 composite.png
zx81 composite.png (63.86 KiB) Viewed 621 times

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1024MAK
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Re: Lambda colour kit

Post by 1024MAK » Thu Oct 10, 2013 12:09 pm

TMAOne wrote:I hope there is a also a link on the Lambda color module as originally suggested. I have just obtained a European module, and am in Canada, and so far have not been able to make it work, with either the RF or the monitor output. My color TV's don't much like the stock Lambda either--the only video I have working well is an early 80's vintage black and white TV, which is hardly the ticket for color work.
The crystal shown on the schematic for the POWER3000 in this post is a 4.4336 MHz for use with PAL colour systems. I do not see any provision for any other colour system in this schematic. Of course, your unit may not be the same.
TMAOne wrote:I haven't tried the module on a ZX81, and am not sure if I dare to do that experiment. The color module is expecting inverse video. Would that be a problem 1024MAK?
I'm not sure. If the edge connector pin-out is the same (and only if it is the same), If it were me, I would try it and see. But I am in the UK with a selection of PAL TV's to try it on ;)

Mark

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1024MAK
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Re: Lambda colour kit

Post by 1024MAK » Thu Oct 10, 2013 12:17 pm

pemilsson wrote:Right now I'm focusing on getting my Swedish ZX81 work with my fairly new American Toshiba LED TV and it seems to be a challenge.
I have made the video conversion described here viewtopic.php?f=7&t=1125&start=10
I added a zero ohm jumper at R30 to get the 60Hz
I have tried to send my video signal through my home video amplifier in a hope that it might adjust the signal.

Unfortunately none of the above have convinced my TV to show anything.

I now also done some measurements to verify that the signals looks good.
Could it be that I don't have correct 0 ref in the signal?
It could be that your TV just does not like the Zeddy video signal.
You could try adding a 100uF 16V electrolytic capacitor in series between the composite video output from the ZX81 and the lead to the TV. The positive lead of the capacitor goes to the ZX81 and the lead of the capacitor goes to the TV.

Do you have another TV to try (an older CRT type is best)?

Mark

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PokeMon
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Re: Lambda colour kit

Post by PokeMon » Thu Oct 10, 2013 2:48 pm

Your signal looks perfect.
Try another TV - not the Toshiba LED.
Many newer TVs are very strict about the timing (64us horizontal / 16.6ms vertical).
So if your signal has too much tolerance regarding the ZF filter used (not as exact as a crystal) your TV might show nothing.
Better would be an older TV, maybe a CRT would be best if you have somewhere.

My ZX80CORE doesn't work with my small XOMAX LED TV. The ZX81 is perfect on this. No not perfect but can see something. :mrgreen:
My ZX80CORE shows a very clear and stable picture on a maybe 20 year old CRT TV via Scart.
I think this is because of signal timing tolerances.

pemilsson
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Re: Lambda colour kit

Post by pemilsson » Fri Oct 11, 2013 3:28 am

Thanks all of you for all advices, this is the only TV I have right now but will now look around for options.
Have anyone tried to use a home movie amplifier that convert composite video to hdmi?

Or maybe a converter like this http://www.amazon.com/Mini-Composite-CV ... rid_pt_0_1

gozzo
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Re: Lambda colour kit

Post by gozzo » Fri Oct 11, 2013 5:57 pm

There is a possible way or two round this modern TV problem, a 'Display Electronics' 'TELEBOX' ,if you can find one, basically a modified cable TV receiver unit (analogue, of course!) with RGB and sometimes composite output, some models also with audio, and also a Citizen TR30 TV receiver unit which fitted on its M322 monitor to turn it into a TV (the TR30 has audio and composite output) both are basically 'obsolete' but the Telebox MAY still be around, haven't been able to track down any of the Citizen units so far....
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PokeMon
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Re: Lambda colour kit

Post by PokeMon » Fri Oct 11, 2013 6:20 pm

pemilsson wrote:Thanks all of you for all advices, this is the only TV I have right now but will now look around for options.
Have anyone tried to use a home movie amplifier that convert composite video to hdmi?

Or maybe a converter like this http://www.amazon.com/Mini-Composite-CV ... rid_pt_0_1
Well - some Video/VGA Converter are working. I did try one myself, which wasn't successful. Fortunately I could send it back due to EU right. :mrgreen:
The problem is, that the newer video chips allow less tolerances than the old analog technique did. So this maybe work - maybe not.
The next version of my video mod will provide a VGA interface as well to allow connection of standard computer monitors with VGA.
But this could take a while to be ready for sale ... ;)

pemilsson
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Re: Lambda colour kit

Post by pemilsson » Wed Oct 23, 2013 3:17 am

Voila :)
I got it up and running on my LED TV. It doesn't work when connected to video in but when I connected to one of the component inputs I get a perfect white stable screen.
The Lambda colour kit is another story I get some weird distorted dots in the down left corner and they changes when I'm typing but it's nowhere readable.
I also have another issue with reading tapes but I will post that in another thread.
Thanks everyone
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ZX81 running.jpg
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