Sinclair ZX80 / ZX81 / Z88 Forums

Luckily I was working from home today so tore into this immediately after finishing up :) Got the new ULA in (thanks again, Moggy!) and the CCB wired up: https://c2.staticflickr.com/6/5630/22094716774_ef6f1a18fb_c_d.jpg Attached the scope to the input, immediately things are looking better: https://...

Received the replacement 2C158E ULA from Moggy earlier. Looking forward to having a look at this later

B

For those interested, here are a couple of photos of the patient in question: As I received it: https://c1.staticflickr.com/1/631/21850966644_4c37320001_c_d.jpg I gave the case a quick clean, repainted the logo, replaced the membrane and missing feet: https://c1.staticflickr.com/1/680/21851014904_94...

I've seen some occasional rainbow ghosting effects off of my ZX80Core when its CCB is slightly out of adjustment, so I'd imagine some tweaking will be required :) Again thank you very much Moggy, I'm in your debt :) I'll 'scope the output from this new ULA for all to see when I get my grubby mitts o...

Moggy - PM incoming

Not to worry Mark. I think tonight's 'scoping and your reminding me of the three level ULA output makes clear that either this is a characteristic of the 158 ULA, or mine is faulty in some way. Either way, as the black level is at the same voltage as the sync pulse, the CCB module can't tell the dif...

Correct, there are only two levels on the input trace, even after adjusting down to the 100mV range there's negligible difference in voltage level between the sync pulse bottom and the black level (coupled through a 10uF cap): https://c1.staticflickr.com/1/778/22232090229_21bdb964c9_b_d.jpg Screen d...

Ok, here's a capture with R1 turned all the way to the right, and R2 adjusted so the cursor can be seen. Input from the ULA is the yellow trace, output from the CCB is the green, 1v/div. https://c2.staticflickr.com/6/5655/21795945033_6e53b5de9b_b_d.jpg Input white level measures as 4.21v, sync and b...

Cool, I'll try this again tomorrow. There's very little adjustment leeway though - turning R1 a hair either way loses all signal on the scope, and very fine adjustment is needed to get the back porch to fire.

B

Hi all, Just wondering if anyone has managed to successfully fit a CCB module to a ZX81 with the early 2C158E ULA. I have such a machine, that gives the following output when simply composite modded: https://c2.staticflickr.com/6/5732/22393467795_f0727d5f7e_c_d.jpg 'Scoping this output gives the fol...