FPGA replacment for the ZX8301 ULA and more

[Pr0f]

Amazing to see the progress being made here

[Andrew]

Great work! Looking forward to using one

[Peter]

Ok I have already ordered some pcbs of a more compact version of the basic ULA and after testing the new pcb I will order cplds to build some.

Is there still hope for this compact "pure" ULA replacement, or was it cancelled in favour of the 68008/FPGA project?
I'm still very interested in the former. It is much neater than the previously published designs.
On my main QL the ZX8301 seems close to death, so I'm quite eager.

[lliont]

Is there still hope for this compact "pure" ULA replacement, or was it cancelled in favour of the 68008/FPGA project?
I'm still very interested in the former. It is much neater than the previously published designs.
On my main QL the ZX8301 seems close to death, so I'm quite eager.

Yes I got the pcbs, I'm waiting for few cplds

How can you tell it's near death?

[Peter]

Looks good, thank you very much!
At times I have no video signal on power up. After two or three attempts it then works.
Contact cleaning and reseating did not have any lasting effect. So I guess the ULA is is dying...

[lliont]

a chip NDE (near-death experience)

[stephen_usher]

Looks good, thank you very much!
At times I have no video signal on power up. After two or three attempts it then works.
Contact cleaning and reseating did not have any lasting effect. So I guess the ULA is is dying...

Sounds like a dodgy socket to me.

The original ones are single wipe and the springiness of the leaves decreases with each insertion.

My first step would be to replace it with a modern double wipe one. If you're good with a desoldering gun then you can do it yourself, otherwise ask someone with a lot of desoldering experience as you don't want to damage the PCB.

[Peter]

Sounds like a dodgy socket to me.

That would be mechanical and not explain why it comes up with the second or third power-up.
In any case, the ZX8301 is a weak point and the upcoming compact replacement will be an important spare part.

[stephen_usher]

Sounds like a dodgy socket to me.

That would be mechanical and not explain why it comes up with the second or third power-up.
In any case, the ZX8301 is a weak point and the upcoming compact replacement will be an important spare part.

Oh, I've seen that failure mode with dodgy sockets! The power cycling causes enough extra warmth to expand the metal enough to just make enough contact (theory).

[Pr0f]

It's worth the effort of cutting out the old socket, desoldering the pins individually to avoid damaging the thru hole vias, and then soldering in a good quality turned pin socket.

But the Zx8301 are also subject to some fragility on the video outputs too, and are so easily damaged...