L8300/P3000 Monitor output..?

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Thrash75
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L8300/P3000 Monitor output..?

Post by Thrash75 » Wed Oct 30, 2019 7:38 pm

Hello smart people, :)

I recently got hold of a Power 3000. I already had two Lambda 8300. When I use the "monitor" output (which I assume is composite, or what?) to connect to my modern LCD TV, I get an all white image. But if I connect it to my old PHILIPS CM8833 crt monitor, the picture looks fine. I assume something is "missing" in the signal, which the old crt does not care about, but the newer LCD screen demands to show the picture. Or what? :)

Is it possible to modify the Lambda computer, so the signal is accepted on modern screens?
Brian

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1024MAK
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Re: L8300/P3000 Monitor output..?

Post by 1024MAK » Thu Oct 31, 2019 9:04 am

Hello and welcome. You may want to introduce yourself in the welcome area here.

A monitor output is indeed a composite video output.

It is possible that Lambda does not produce the part of the video signal that is known as ‘the back porch’. The purpose of this part of the video signal is to tell the TV / monitor to set the normal black level it will use to the level of the video signal at this point in time. Black and white / monochrome TVs / monitors generally and some colour TVs / monitors will work okay without this part of the video signal. But other colour TVs / monitors will not be happy. The most common symptom is either a black display, or a very dark display with very poor contrast. I’ve not heard of a white display before.

Please also note that if the problem is the missing ‘back porch’, it can affect colour CRT, LCD, LED and plasma TVs. But amazingly some (but not many) LCD TVs will work okay.

But before going any further, I have some questions.

Are you sure that the TV settings are correct for a composite 625 line, 50Hz (sometimes known as a ‘PAL50’) video signal and the correct source (input socket) has been selected?

Is this the same for the all three computers? Do you have any ZX81s to try? Or indeed, any other 1980s 8 bit computers with composite video outputs to try?

Have you tried different brightness and contrast settings on the TV?

Do you have any other TVs to try your Lambda on?

Have you tried the RF output?

It is also possible that there is a different problem. But may be difficult to diagnose without measuring the video output of the Lambda using expensive test equipment.

There is a solution to ZX81s that don’t produce a ‘back porch’. In fact, there are a number of different solutions, both DIY, ready build modules and professional fitting services. These should work with a Lambda, if the problem is in fact a missing ‘back porch’.

One of the popular modules is PokeMon’s ZX8-CCB available here.
The main competitor is ZXVid. Both involve soldering. The ZXVid can be professionally fitted.

Mark

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mrtinb
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Re: L8300/P3000 Monitor output..?

Post by mrtinb » Thu Oct 31, 2019 9:33 am

Great to see another Dane in the forum. I've posted my discoveries with Lambda 8300 here in these parts of the forum. Most discussions on this page is about the ZX81 though.

P.S. If you have any printed material on the Lambda in either English or Danish please let us know. (We already have the manual in Danish, English, German and Chinese scanned, and we have the PC8300 ROM Buch scanned, and personally I have a Danish software book that covers both ZX81 and Lambda 8300)
Martin
ZX81, Lambda 8300, Commodore 64, Mac G4 Cube

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Thrash75
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Re: L8300/P3000 Monitor output..?

Post by Thrash75 » Thu Oct 31, 2019 1:16 pm

Hello Mark,
1024MAK wrote:
Thu Oct 31, 2019 9:04 am
Hello and welcome. You may want to introduce yourself in the welcome area.
Thank you! :) Done.

1024MAK wrote:
Thu Oct 31, 2019 9:04 am
It is possible that Lambda does not produce the part of the video signal that is known as ‘the back porch’.
1024MAK wrote:
Thu Oct 31, 2019 9:04 am
The most common symptom is either a black display, or a very dark display with very poor contrast. I’ve not heard of a white display before.
I'm glad to throw another puzzle into the mix. Tech can be so strange. :) See attached picture.

1024MAK wrote:
Thu Oct 31, 2019 9:04 am
Are you sure that the TV settings are correct for a composite 625 line, 50Hz (sometimes known as a ‘PAL50’) video signal and the correct source (input socket) has been selected?
No. :) My TV don't provide an option for selecting this manually. I think it's done automatically. But I have tried different "Colour Space" settings (Normal or "x.v.Colour"), and "Colour System" settings (Auto, PAL, SECAM, NTSC3.58, NTSC4.43). None make a difference. Oh, and I'm sure it's showing the picture from the Lambda, as the screen goes momentarily black for a short while, if I press RESET.

1024MAK wrote:
Thu Oct 31, 2019 9:04 am
Is this the same for the all three computers? Do you have any ZX81s to try? Or indeed, any other 1980s 8 bit computers with composite video outputs to try?
I do not have a ZX81, unfortunately. Only the Lambda clones. Yes, all three show white picture on my LCD TV, and all three show picture fine on my PHILIPS CM8833. I have tried connecting a C64 to composite on my LCD TV, and that displays fine.

1024MAK wrote:
Thu Oct 31, 2019 9:04 am
Have you tried different brightness and contrast settings on the TV?
Yes, I have. No change, other than changing the whiteness to some degree.

1024MAK wrote:
Thu Oct 31, 2019 9:04 am
Do you have any other TVs to try your Lambda on?
Uh, yes. But it's in storage, and it's a whole process to dig it out. :? But I can do it, if you insist. ;)

1024MAK wrote:
Thu Oct 31, 2019 9:04 am
Have you tried the RF output?
No. I looked for an RF antenna cable for about half an hour, but I can't find any.

1024MAK wrote:
Thu Oct 31, 2019 9:04 am
It is also possible that there is a different problem. But may be difficult to diagnose without measuring the video output of the Lambda using expensive test equipment.
All I have is a multimeter.. :lol:

1024MAK wrote:
Thu Oct 31, 2019 9:04 am
One of the popular modules is PokeMon’s ZX8-CCB available here.
The main competitor is ZXVid. Both involve soldering. The ZXVid can be professionally fitted.
Interesting! Especially the first one, since it's inexpensive. :) I don't mind soldering, as long as the difficulty is not too high. I hate SMD stuff..

Thank you for assisting me! :)
Brian

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Thrash75
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Re: L8300/P3000 Monitor output..?

Post by Thrash75 » Thu Oct 31, 2019 1:17 pm

Hejsa Martin,
mrtinb wrote:
Thu Oct 31, 2019 9:33 am
Great to see another Dane in the forum. I've posted my discoveries with Lambda 8300 here in these parts of the forum. Most discussions on this page is about the ZX81 though.
Thanks, yeah. It was somewhat popular in Denmark. :) I have read some. I will read more in-depth. I saw some software restoration projects. So cool you guys do that. Much respect! I hope to load some games onto it, somehow. Maybe the iPod could work for that.. :lol:

mrtinb wrote:
Thu Oct 31, 2019 9:33 am
P.S. If you have any printed material on the Lambda in either English or Danish please let us know. (We already have the manual in Danish, English, German and Chinese scanned, and we have the PC8300 ROM Buch scanned, and personally I have a Danish software book that covers both ZX81 and Lambda 8300)
Seems like I can't contribute, then.. :( All I have, is two Danish printed Lambda 8300 manuals. That book of yours sound interesting. :)
Brian

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mrtinb
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Re: L8300/P3000 Monitor output..?

Post by mrtinb » Thu Oct 31, 2019 2:01 pm

(One problem with the Lambda 8300 is that it comes with two different ROMs. ROM version 1 is black screen with blinking cursor. ROM version 2 is the text READY, and a blinking cursor. ROM version 2 supports the Lambda Colour Pack if attached. Software made for version 1 won't work on version 2 and the other way around. So if the software does not work, it could be a corrupt load, but it could also be made for a different ROM version. ROM version 1 was too similar to ZX81, and because of a lawsuit ROM version 2 was changed quite much.)
Last edited by mrtinb on Thu Oct 31, 2019 4:09 pm, edited 1 time in total.
Martin
ZX81, Lambda 8300, Commodore 64, Mac G4 Cube

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Thrash75
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Re: L8300/P3000 Monitor output..?

Post by Thrash75 » Thu Oct 31, 2019 3:44 pm

Thanks for info, Martin. I will watch for that. Mine is version 1. :)
Brian

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