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HOWARDHB wrote: ↑Thu Jun 20, 2024 11:12 pm Only Basic4 and SYN600.

OK, should work and give you the Monitor then.

What RAM do you have installed and in what sockets?

IIRC if using just 2 RAM ICs they need to be in the 2 sockets closer to the edge. When I built mine I didn't realise and had the 2 ram chips inboard nearest the video RAM and IIRC got random characters on screen. Might be worth checking if you only have 2 RAM ICs installed.

2 video RAM chips U51, U52 (next to CHARGEN rom) and 2 RAM chips in the "outer" two positions, U31 & U39, so 1K at the lowest address.

HOWARDHB wrote: ↑Fri Jun 21, 2024 10:51 am 2 video RAM chips U51, U52 (next to CHARGEN rom) and 2 RAM chips in the "outer" two positions, U31 & U39, so 1K at the lowest address.

Did you mean the video RAM in U39 & U40 and the lowest RAM in U31 & U45 because those positions don't match with my schematics or parts layout.

HOWARDHB wrote: ↑Fri Jun 21, 2024 10:51 am 2 video RAM chips U51, U52 (next to CHARGEN rom) and 2 RAM chips in the "outer" two positions, U31 & U39, so 1K at the lowest address.

My bad, video RAM U39 and U40, and program memory, U31 and U45.

If you still have a scope to hand, and you've checked what @bxdanny suggested, it's worth checking what the address and data lines and other pins like sync are doing on the CPU, see if you see any activity as it kinda feels like the CPU isn't running or it's in a halted state.

02 clock is missing.
WHERE oh where does it originate?

Edit:

SUCCESSSSSSSS
Replaced U20 and voila!

HOWARDHB wrote: ↑Sat Jun 22, 2024 7:22 am 02 clock is missing.
WHERE oh where does it originate?
The schematic is NOT clear...

It originates in the 6502, phi2 and phi1 are outputs based on the phi0 clock input IIRC.

The service manual (I've attached it, just remove.txt from the end) shows phi2 quite well.

Thanks for the manual!

I was looking for the processor clock signal O2, without the processor in the circuit. I was expecting it to be an INPUT.

Doh!

Now that it boots and reports correct memory size, I'm going to get the tape input working...

The ancient little CRT monitor that I was using does sync the video ok, but chars are slightly off the edges. I will open it and see if I can adjust the horizontal width?
But, for now the LCD seems to work perfectly, though not period correct!

.... and the compulsory test...



I'm smiling

H.

That's great news, well done