Sinclair ZX80 / ZX81 / Z88 Forums

Found it "printed" in my hands. I just overlooked it. Thanks!

Dessony

I just uploaded a solder side sketches of the ZXmore.

Thanks,
Dessony

Hi,
this looks like the delay of the row counter enable signal does not work as expected.
At least seem to be no relevant delay at all.
Can you proof or measure if R26 is 3k3 (3300 Ohms) and C9 is 47nF ?

So resistance between pin 10 of IC6 and pin 12 of IC11 must be 3.3k - you should try to measure with a multimeter to be sure.

Hi William,

this might be an issue with the actual version 1.7 which does not support NTSC video mode properly.
This gives at least the rolling effect as it hard presents PAL signal whatever you jumper.
You should be still able to switch to instance 1 with the manual rom switch giving the NTSC mode for ZX81 (without ZXmaster control option). This could be another test you could do - take care to set the PAL/NTSC jumper properly for this test.

There might be a dependency between both effects but in fact this may be two different errors as well.
I am still working on the 1.8 version to get it stable for publishing.

Karl

Pokémon (Karl),

I quoted you, "Can you proof or measure if R26 is 3k3 (3300 Ohms) and C9 is 47nF ?

So resistance between pin 10 of IC6 and pin 12 of IC11 must be 3.3k - you should try to measure with a multimeter to be sure."

Your suspicion was right. My multimeter shows me its reading as 3.27 X 20K. The resistor 26 reads 3270 ohms. I see a capacitor 9 as 473. Yes, it's 47nF(0.047uF to the Americans).

My board has the NTSC jumper set. I am hooking the board up to these CRT color TV and CRT monochrome monitor as you can see from these photos, I submitted here.

William

Thanks - so let's wait the update first to release 1.8 supporting NTSC again.
What about choosing instance 1 manually with the rotary switch in position 1, does it show up ZX81 ?
This way NTSC option should work as well if jumper set.

Good news, yes, I finally saw a inverted "K" on the screen after I fiddled a monitor's vertical size knob! Also the screen, itself, was steady.

Also I tested my ZXmore on the CRT color TV. The board also passed its test! I will test the board on the flat panel TV soon.

Also I put ZXpand and ZXmore together, they work fine. I will test my joystick interface soon.

One further question - when you start ZX81 manually - is the issue with the line counter offset (starting with lower pixel lines on top) ?
So very easy to detect if the K is in the middle of the black block - one black pixel line on top and one black pixel line on bottom of the K cursor.