Spectrum Computing

Hi Both Thank you for your detailed responses. Mark, the command returns the correct result for a 16K machine. The reason I checked the ULA is I know I damaged a pad when I desocketed it, so I totally removed it (good practice) to find that it works, and it also allowed me to properly repair the tra...

Hi everyone Hoping you can help me solve an issue. I think it's a hardware issue but I'm not sure at this point. I've been refurbishing an issue two, jobs performed: Recap DCDC Mod (following Retroleum's instructions) New membrane Desocket and heatsink for ULA I know the ULA works as I tried it in a...

Hi I have an example script I'm modifying, and I'd like find a faster way to achieve this... DEF FN m$(q$)=q$(2 TO )+q$(1) The purpose of the function is shift a line of space invaders along by one cell, moving the last back to the front of the line. It's just so slow the game really isn't much fun!

Any photos of the board and its chips?

Do the pixels move while it's on or is it frozen?

Recapping, Composite mod, cleaning up and DCDC Modding an Issue 3, while drinking coffee.
Please tell me if you see any mistakes or inaccurate information


https://www.youtube.com/watch?v=AbIJza7 ... qz0PFOw0V0

Your clip of the machine running with no RAM looks a lot like what I had here https://youtu.be/OYsv7Jaseu8?t=326 That came down to a broken trace under the RAM sockets. Have you checked continuity on all the lower RAM pins (Except Din and Dout) between the farthest left (IC13) and the farthest right...

A small update for you. - I cleaned the case and keyboard - Did the initial tests, all OK - Plugged it in, heard the whine, OK - Checked voltages, 12V is 12.7V but generally OK, better than expected - Plugged it into my TV...... https://i.postimg.cc/bGdxsmxG/1.jpg https://i.postimg.cc/y3CcpBw9/2.jpg

Honestly I don't think there's a whole lot to do as long as nothing too weird is happening with the electronics. I would love to restore the face plate, but what can I do except try to paint the areas that have flaked off? I wouldn't be able to match the colour and I don't know any methods to print...

Honestly I don't think there's a whole lot to do as long as nothing too weird is happening with the electronics. I would love to restore the face plate, but what can I do except try to paint the areas that have flaked off? I wouldn't be able to match the colour and I don't know any methods to print ...

I think I got lucky with this one!
It looks in really good shape except for the face plate.
Haven't done any checks yet... just a first looksee
https://youtu.be/RHPBncMMBpM

How did you disable upper RAM?

How useful would be if i had an oscilloscope in this specific situation? You could check the power rails and determine if there’s too much ripple on each. You could also examine digital signals and see if there are any irregularities. A data analyzer would be even more useful. This was my thought a...

https://youtu.be/OYsv7Jaseu8

Hi all.
This is the repair I've been posting about in another thread.
Quite an interesting, but in the end easy job.
Enjoy. Please let me know if I say anything incorrect.
4K should be processed and ready later

Cheers

The copper tape repair went beautifully, I captured it with the microscope and the spectrum now boots correctly

Thanks Mark.
Yes I'm a bit concerned about the heat gun. No problems so far but I find it a bit unrefined when the board gets a bit wobbly with the heat

https://i.postimg.cc/JGMKrhjg/signal-attachment-2020-05-06-092515.jpg For you feel better pleasure. Top side just had a few traces, bottom was a disaster ground. I did the full nuke on removing all the upper ram and logic chips and for some reason that section gave me all the trouble (ram). Rest wa...

I've never used it before but it seems like a good solution, fingers crossed, if I make a mess again it's going to get harder to fix

Time to put it away until the copper tape arrives... Copper tape? You mean the desoldering stuff? No it's a sticky copper tape for electronic repairs. You tidy up the damage, stick this over and solder it in. I tried to make the link with a small wire but buggered it up https://i.postimg.cc/y3dHvsn...

I found my broken track, hooray!

But I got impatient and made it worse.
Time to put it away until the copper tape arrives...

My replacement Z80 was actually a Z84C20 with is a PIO chip. What, and it didn't work? :lol: I'm impressed that anything happened. I got the screen shown in the post above and the blocks were changing. The chip did get quite hot though... It got me thinking, could you make a simulation so accurate ...

It looks like a bad joint on the topside of the board as there is continuity from the socket to the underside

Hi! Sorry, I like to share, I hope it's interesting. After reading some of the Z80 Technical Manual (Great little book happy to have found it) I realised a silly mistake. My replacement Z80 was actually a Z84C20 with is a PIO chip. I put an actual Z80 in and got a white border with some more familia...

C80 - should be 22uF, was 1uF - :shock: this will affect the power output of the DC/DC converter :-( C74 - should be 4.7uF, was 22uF - :shock: this will affect the response time of the regulation of the +12V line :-( C27 - should be 1uF, was 4.7uF - that will just give a slightly longer reset pulse...

Slight diversion from the original thread but I just noticed that whoever recapped this board used the wrong rating of capacitor in a few locations. ........might be a good place to start! Different capacitance? Different voltage? Higher value? Lower value? In most applications, the next value up, ...

Slight diversion from the original thread but I just noticed that whoever recapped this board used the wrong rating of capacitor in a few locations.

........might be a good place to start!