help with 464 replica board

[salvogendut]

I have built a 464 replica board (minus the sound chip) and was trying to test it. All I get is a grey screen and some flickering (see pics). Some chips get warm, the GA does, the ram chips do, IC107 and IC108 and some of the logics do but no change in the Z80 , it stays cold. Any idea of where to start looking for activity? I do not have an oscilloscope but I have a multimeter which can do some limited frequency checks.  When I turn on the switch the screen stays grey and kinda flickers a bit with some darker horizontal lines. When I turn off there is no activity, just a grey screen.

[Bread80]

I notice you don't have D101 populated. That's part of the power-on reset circuit, so a required component.

[salvogendut]

I notice you don't have D101 populated. That's part of the power-on reset circuit, so a required component.

Dang!


What a sight you have there, my friend. I could not see it due to the capacitor that was hiding it from me. And pretty soon after I soldered the 1N4148 to the board... stil a grey screen. The Z80 was cold as ice. Damn! I decided to take the Z80 from my old 464 and that's when the magic happened. Apparently the Z80 I had put in the replica board was either fake or fried. This little dude here:



So after that I put the sound chip as well and tried my hand with the diagnostic cartridge and everything looks ok. I guess I am gonna need to buy a Z80 for it.





I owe you a beer @Bread80!!!

[Brocky]

This little dude here:

if you have a closer look at that 'z80' you'll find its a PIO and not a CPU!

well...theres your problem!

i have one of these replica boards, they are very nice

[salvogendut]

This little dude here:

if you have a closer look at that 'z80' you'll find its a PIO and not a CPU!

well...theres your problem!

i have one of these replica boards, they are very nice

Yeah I realized yesterday after I had made this post that this thing is indeed NOT a CPU! It could have never worked. Very nice board indeed and I had a lot of fun making it. It was my 'study' project as I decided to learn  soldering skills. I am gonna make a keyboard as well and then fit this into an empty 464 case some day

[orzel]

Where do you find/source the RAM chips ??

[salvogendut]

Where do you find/source the RAM chips ??

I got mine off ebay