Andyroo wrote: ↑
Sun Aug 04, 2019 5:30 pm
That looks a lot harder to solder than the ZX80 I bought so many (many many) years ago
At least I could cope with through hole - cannot manage this new fangled SMD type stuff at all
Must say though - the board does look neat and tidy. Signs of true love.
I was surprised that you can still buy cassette recorders (even Amazon stocks some) - I know I marked mine with snopake and covered it in tape once I had the volume just right. Oddly enough, I miss the screech of these and acoustic modems
SMD isn't that difficult, just fix two opposite corners first, then add a lot of flux, and drag your iron across the pins while adding a bit of solder.
If you get the hang of it its quicker that soldering the same in DIP format. I tried to use somewhat manageable size components, 0805 size, smaller will be too small to handler most people, but 0805 is doable, even for a quite old guy like me (I'm 63).
If I had used standard pin through hole components the PCB would have to have been quite a lot larger, my re-implementation of sinclairs ULA takes a lot of logic, but it does have some extra's, such as 32K RAM, back porch logic, which means it works with a modern TV, it even has 8 GPIO outputs and a GPIO input, These can be used for several things like controlling a robot, or an LCD, and even 4-bit sound output. In theory it also has a turbo switch, although video is glitchy when using both acceleration options it has, it can run in double speed mode when using "fast mode", or with a 10% increase in slow mode (with stable video).
The cassette input is optimised for weaker signals, and a wider signal range, you can play wave files trough your smartphone to it, works great!
I now have also uploaded a programmable sound generator (AY-3-8912 PSG) expansion board for my ZX81+35 to GitHub so you can play chiptune music on a ZX81, should be compatible with software written for the ZON PSG board (anyone still remembers dancing demon?) As an extra I added a SD-card socked, using the GPIO ports of the AY-3-8912 chip. Hopefully someone will test it, and write a software driver for the SD-card, so you can use SD cards instead of cassette tapes with it. more info here: https://github.com/mahjongg2/PSG-for-ZX ... ZX81-clone