Search found 181 matches

by TMAOne
Mon Jun 29, 2020 3:06 am
Forum: Hardware
Topic: Does Anyone Recognize This Pattern?
Replies: 19
Views: 7581

Re: Does Anyone Recognize This Pattern?

The problem with the keyboard turned out to be the ever-more-quickly failing ULA I was using in the unit. It will alternately accept input in the "J" column (for LOAD), or in the far column (for Shift-P double quotes, and Enter), but never both on the same boot-up. Stymied. The one good ULA I own, d...
by TMAOne
Sun Jun 28, 2020 9:54 am
Forum: Hardware
Topic: Does Anyone Recognize This Pattern?
Replies: 19
Views: 7581

Re: Does Anyone Recognize This Pattern?

Awesome post as always Mark. I had not heard of bugs in digital multimeters before. It caught me out completely. I replaced every component of the -5V circuit, and when that didn't work I pulled all 8 4116's thinking there must be an internal short in the chips. It was only when the bare board STILL...
by TMAOne
Fri Jun 26, 2020 10:17 pm
Forum: Hardware
Topic: Does Anyone Recognize This Pattern?
Replies: 19
Views: 7581

Re: Does Anyone Recognize This Pattern?

A lot has happened since I last posted to this thread. I'll try to review as I go so that any interested reader need not go back to re-read the previous posts. Mark and others had generously offered some great advice to assist me in attempting to revive an old Spectrum 48K I discovered in my possess...
by TMAOne
Sat May 02, 2020 11:52 pm
Forum: Hardware
Topic: ZX Spectrum + : no boot
Replies: 32
Views: 1279

Re: ZX Spectrum + : no boot

I just found a neat resource here: http://hardware.speccy.org/reparar-i.html. It would suggest C44 from comparison with your picture. You did a complete recap, but maybe there's still a fault there, or you got a bad part? I don't know.
by TMAOne
Thu Mar 12, 2020 9:24 pm
Forum: Hardware
Topic: Does Anyone Recognize This Pattern?
Replies: 19
Views: 7581

Re: Does Anyone Recognize This Pattern?

Sorry for the delayed response. Life tends to get in the way of working on this. And I think it's time to give it up. More on that presently. To answer the specific questions and areas of concern first, yes either the heat sink was fitted for testing, or a clamp-on auxiliary was used and power-ups l...
by TMAOne
Fri Mar 06, 2020 9:18 am
Forum: Hardware
Topic: Does Anyone Recognize This Pattern?
Replies: 19
Views: 7581

Re: Does Anyone Recognize This Pattern?

Is this progress? It certainly is different,... Soooo, I got the 2nd vLA82 in the mail, and had no real issues replacing the socket and putting it in. But rather than the crisp black and white stripes I had (if only briefly) before, this is what I get now: 20200306_014724.jpg The image is blurry--th...
by TMAOne
Sun Feb 09, 2020 1:22 pm
Forum: Hardware
Topic: Does Anyone Recognize This Pattern?
Replies: 19
Views: 7581

Re: Does Anyone Recognize This Pattern?

Yep, noise is what I had. But also at ULA 32, so the replacement ULA has been killed. Not sure how the computer and I managed to do that, but after some generous support from Charles, I have a second vLA82 on its way through the post. Efforts to revive this computer will have to wait for the mail sy...
by TMAOne
Fri Feb 07, 2020 5:04 pm
Forum: Hardware
Topic: Does Anyone Recognize This Pattern?
Replies: 19
Views: 7581

Re: Does Anyone Recognize This Pattern?

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?
by TMAOne
Fri Feb 07, 2020 9:22 am
Forum: Hardware
Topic: Does Anyone Recognize This Pattern?
Replies: 19
Views: 7581

Re: Does Anyone Recognize This Pattern?

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...
by TMAOne
Thu Feb 06, 2020 11:03 pm
Forum: Hardware
Topic: Does Anyone Recognize This Pattern?
Replies: 19
Views: 7581

Re: Does Anyone Recognize This Pattern?

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...