Sinclair ZX80 / ZX81 / Z88 Forums

Yeah I was afraid of that. Pretty much wraps it up--I've no clock whatsoever on ULA 32 or CPU 6. ...She's dead, Jim.

The ULA had been working, but suddenly quit. Could a failing capacitor in the -5V power circuit do that?

Sorry for the triple post. I'm slowly learning to use this o'scope, like when to ignore "noise" zoomed in to look like something its not. Also looking at my ZX81 as an experimental "control" to give me some idea of what I should be seeing when I look at the Spectrum. I think I've clock problems. The...

Okay no pocket oscilloscope. Instead I'm using a CRT one with an "Auto" button for o'scope neophytes. I thought that the output to the monitor and pin 17 of the ULA would be a good set of brackets to start, but already I don't like what I see. Pin 17 of the ULA: Scope 001 ULA 17.jpg Final output: Sc...

I appreciate that Mark. I will definitely consider it once the determination to prove this computer viable is satisfied. Seems like some parts I will have to order, and I usually take the eBay/China/slow boat route, so that may take a while. In the mean time, I did complete the re-cap before reading...

Wow Mark, that was just the kind of precisely-targeted information I scarcely dared hope for. Thank-you! Unfortunately, I have not yet been successful in figuring out the two issues that happened after taking that picture, so I couldn't follow up right away. There were a total of 3 issues when I sta...

Though I have been active in the ZX81 portion of this forum, I've not had a reason to post here before now. But recently while re-arranging scrap boards, parts, and whatnot, I came upon something I'd completely forgotten I had. 01.jpg 02.jpg It is an Issue 4A Spectrum 48K, picked up at a hamfest yea...

It's not often I disagree with Mark but as audio is my bag I would say this WAV is very mechanized ,lacking as it does the usual aural artifacts I think it's me you were disagreeing with Moggy, so Mark's reputation is intact. :) And I am confused. This is your test file. test_2020-01-28_21-59-08.jp...

Hi 8008guy, Regarding question 1: I could NOT load it with the Eighty-One emulator. (Other .wav's I have do load successfully.) Two things jump out at me when I look at your .wav file with a sound editor. A) I'm not familiar with p2wav, but this file looks as if it was recorded from analog equipment...

See? There goes one now,...

Sounds like you're on the right track with corrupt ROM or ULA. The string that gets echoed from the one-byte PRINT command code is actually " PRINT ", or space-PRINT-space. Same idea with POKE. That mapping seems to be partially corrupt, and the echo strings contaminated. I'll leave it to the smarte...