ZX8-CCB vs ZXVid

[Lardo Boffin]

And thanks to 1024MAK for the soldering advice!

Ok this is now starting to sound like an award show speech...

[PokeMon]

So congratulations, good work.
The picture on the CRT looks much better than on the LCD.
I am unsure, the picture is a bit far left. Normally it should be centered when printing the maximum column of 32. You can just type the following program in:

10 PRINT "A";
20 RUN

This will stop when the screen is full.
The distance left and right should be approximately equal.

Maybe you try to adjust the picture with the trimmers, as the factory setting might be an approximation only. The voltage levels vary a little bit on ULA type and production series. You find more information here. If you take a picture from the board/trimmer settings first, you can easily put the old setting back when experimenting. Most cases the left pixel trimmer should be sufficient to adjust but you may try a different sync trimmer setting as well. Best adjustment can be done with a CRT TV as it responds immediately on the settings while the LCD may have some delay or even show no picture when somethings is wrong with the signal.

http://sinclairzxworld.com/viewtopic.ph ... 1&start=30

Good luck !

[Lardo Boffin]

So congratulations, good work.
The picture on the CRT looks much better than on the LCD.
I am unsure, the picture is a bit far left. Normally it should be centered when printing the maximum column of 32. You can just type the following program in:

10 PRINT "A";
20 RUN

This will stop when the screen is full.
The distance left and right should be approximately equal.

Maybe you try to adjust the picture with the trimmers, as the factory setting might be an approximation only. The voltage levels vary a little bit on ULA type and production series. You find more information here. If you take a picture from the board/trimmer settings first, you can easily put the old setting back when experimenting. Most cases the left pixel trimmer should be sufficient to adjust but you may try a different sync trimmer setting as well. Best adjustment can be done with a CRT TV as it responds immediately on the settings while the LCD may have some delay or even show no picture when somethings is wrong with the signal.

http://sinclairzxworld.com/viewtopic.ph ... 1&start=30

Good luck !

Thanks. I'm struggling to get a good image. When I do the 10 PRINT "A"; etc. I get the following which is not too bad:-

IMG_5198.JPG

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Note that the top and bottom lines are perfect but the other lines are a little slanted.

When I switch on my ZXpand and launch commander I get the following:-

IMG_5197.JPG

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I have tried many adjustments but cannot get an image in the correct place or layout.

Is this indicative of me being rubbish at adjustment or a problem with my zeddy? E.g. a dodgy ULA or other component causing interference?

Any advice appreciated!

Lardo

[Lardo Boffin]

Note that I am pretty sure I got the same layout issue with ZXpand commander before fitting the board, albeit much more fuzzily!

[PokeMon]

I saw this destructed ZXpand picture before but I can not remember what the problem exactly is. I think it is a ZXpand issue which is not directly related to ZX8-CCB. The movement of the first pixel line a bit to right and at the other rows a bit to left I have not seen before.

I guess this is a problem of the TV when clamping the video signal. It seems to depend on video content. You could try some mixed screen content, graphic chars to see a dependency. Sometimes video signal is feeded in through a capacitor inside the TV. The out coming DC level depends then on the video content (approx white and black parts). You could try a inverted and a normal space alternating to see, if you then have sharper vertical lines. The "A" seems to move a bit to right like an arrow.

It could be by the way, that the picture is moved a little to the left through the old TV. Do you have any video signal from another source (camcorder or similar) to compare ?

There could be ULA dependencies as well but for me it doesn't look like, at least not obviously. By the way - did you cut the tracks to the modulator or are they still present ? There might be some issue when feeded in in parallel.

[Lardo Boffin]

Thanks for the feedback!

I have a composite modded speccy that works fine on the same TV, image below:-

image.jpg

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Ignore the poor quality of the top half - that is my camera.
It is slightly over to the left but nothing dramatic.

I previously had a zeddy with a ZXVid which worked fine on this TV and with the same ZXPand. I'm pretty sure the ZXPand itself is ok but I guess it could just not get along with this zeddy - it (the zeddy) hasn't had any capacitors etc. replaced.

I only cut the wire connecting to the output in the modulator, I.e. the part where the cable plugs into it.

Is there anything else I need to cut?

Thanks

Lardo

[PokeMon]

OK then it is not the TV. The wire to be cut should be the middle through hole of the modulator, the right one is 5V and the left is normally empty. This is just to avoid additional load at the ULA output. Could be something with the ULA as well or with power supply. Is there a difference when starting with a cold vs. a self heatened ZX81 ?

Could be a problem with power supply as well. As the connected ZXpand makes the picture more crazy (needs quite much current) it would be a good idea to measure the incoming and outgoing voltages on the regulator with and without ZXpand. Middle pin of the 7805 regulator is GND while left is input and right is output. Would be quite interesting the DC and AC voltages measured (AC applies on input only). The big capacitors in the original power supply could loose capacitance over the time (30 years!) which results in more AC and less DC voltage. So there can be drops on the 5V side through a bad supply. You could use another DC supply as well with 9V regulated, check polarity of connector first. Ring is minus and tip is plus.

[Lardo Boffin]

I have found another power supply which does exactly the same. They are both Spectrum supplies - UK1400's.

It had the same issue displaying the graphics screen but both allow text to be displayed with the ZXPand plugged in:-

image.jpg

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Again the picture is not very good because of my phone camera. On the TV itself it is pretty good.

I will try to let it warm up and then see if I get the same problem.

This is a photo of the modulator:-

IMG_5199.JPG

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I cut the wire to the output plug as well as the two wires connecting to the modulator (on the left, not easy to see in the photo). You can see one of them bent over the modulator case.

[PokeMon]

Hmm - the screen looks better than before. And ZXpand is running. So what did you do to get ZXpand running ?
There has been some distortions in the characters in the pictures before but now all lines are very straight.

[Lardo Boffin]

ZXpand runs fine with just text. As soon as any graphics come along it goes haywire.

I tried your suggestion of printing some graphics characters and the following happens:-

IMG_5200.JPG

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I get the same results with or without the ZXPand so that points back to the zeddy itself I think?