ZX Spectrum Issue 2 Repair and Restoration 

Just a tip regarding that diagnostic software. I had persistent memory issues with a ZX Spectrum 2+, and that diagnostic software was listing errors with different upper ram ICs each time it ran. I swapped out upper ram but it didn't seem to solve the issue. I used an oscilloscope to look at the data lines on the upper ram. I saw rock-solid 5v square waves on every data line. When I looked at lower ram, there was a distinctive ramp on the front side of every square wave, and the average voltage was more like 4.5v. It turns out that an electrolytic capacitor near the ULA was bad, and it was causing this ramping. Lower ram worked fine with this ramping, but the issue popped up when bank-switching parts of upper ram.

Nice fix. When you first powered up the Speccy I thought, oh-oh, this is going to be trouble...I was wrong. Thank goodness for quality diagnostic software; saves a lot of time troubleshooting. Enjoyed! Thanks!

Thanks for this video. I had the same colour banding issue. I resolved it by changing the display cable and tweeking the variable resister on the board that controls the vertical hold and colour adjustment

Never had those things back in the days. But nice to see some of them now. Thanks for the good work!

Love the link to Retroleum. Just what I needed to replace a key contact plunger. Been looking for this part and thought I was going to have to buy a whole key board just to get that one part!

There's also a S-Video mod available which is basically 2 transistors + 2 (or 4) resistors. Works like a charm and gets rid of that annoying color bleed on composite. Another decent mod is replacing the lower 16k bank with 4164 DRAMs - which kills the need for the internal -5V (whenever it would fail it will very likely take the original 16k bank along with it).

And to think it's over 30 years old and it still works! None of the modern consoles will be able to say that 30 years from now...Great vid i really like your channel i'm glad i came across it!

Obviously it's more important that these old computers are working vs their physical condition, however if that were mine I probably would have filled the deep scratches and holes and sanded it back then painted it. Next replaced the faceplate along with the membrane. But that's just my opinion of course. Keep up the videos when possible, always enjoyable.

Spectrum pcbs are natourious for fine cracks, and trace wires are needed for repair.

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If you consider a fully recap the machine rremember in the Issue 2 the C46 is installed the wrong way around, there was a mistake in the silkscreen...by the way keep your videos coming :-D

From my point of view, one of the key of your success is the ability to find those "crazy" testing instruments online.

"Take very good care of it" - omg, what an irony! 🤣🤣🤣

Great stuff! My ZX Spectrum is also showing faults on IC19, almost desoldered the wrong one before I saw your video - must have been looking at a schematic with the wrong numbering.... So, thanks :-)

Just bought issue 2 ,coil makes noise when powered up.but no picture no keyboard click.where do I start ?

very nice thanks for the links

I would recommend when reomivg glue or stickey tape to use a a mild heat gun that way you don't damage the paint but make sure the heat gun is one dow does get that hot or you will melt stuff and when useing it keep it move and don't just hole it on one place

great job...again ;-)

The Speccyyyyyyyyyyy ! Thanks to it, I became short-sighted ! Ah ah !

Hello Jan, i see you clean it with alcohol. Is it ok to use "spiritus"? Is says 85% alcohol. Thank you.

A knife is not recomendable to open a speccy that scratches and damage the stuff

Great stuff =D Where can I find the .tap . z80 file for that diag rom? I followed the link but just see the source and no download?

Hello Jan Beta i have a sinclair 48k that never was opened since 80´s and i tryed to turn it on today but it seems to be dead because the tv screen stills black. Can you help ?

Good 👍 job

I always understood that faulty caps can destroy ram (or was it rom?) on he speccy. Perhaps a cap change would be a smart idea.

Great video! I have an Issue 2 at that i'm hoping to repair, I fixed green screen by adjusting VR1 and VR2 but it doesn't show the black border on boot and although it shows the "Sinclair Research 1982" it has random black pixels appearing, most keys do not work but pressing any that do work results in it showing random gibberish similar to this video and then freezing. Sadly though even though my issue 2 board looks exactly the same as yours, all the chips except for the ULA are SOLDERED not SOCKETED! This is going to make checking for bad RAM a pain in the backside arrgghgh :(

Wondered which game would be your choice of 'go to' game for the Spectrum, like Turrican is on the C64. Expected: Jetpac. Got: Boulder Dash!

You should probably recap it too.

Junior games good stuff . Ballgames on a Sun Ultra even better.

really interesting video. I was wondering what spray you are using in the sockets and on the pcb board?

Can that quick and dirty Composite mod be done on a Nintendo Famicom? :) I have a faulty one but of course its NTSC J for RF and I am in PAL Land so can't test it.

OK, maybe I missed it, but what's with the transistor straddling the CPU?

Hi, i have the same model, but the picture is a lot less sharp than yours, do you think that adjusting the pots may help? There are color dots that "crawl" over the screen, nothing major but i just want so bad the picture to look like yours! Can you help? And yes,did the composite mod

How can I contact you if I want to give you a pile of computers to repair ? I'd need only one fully repaired for me, you could keep all the others.

5:46 Nice effects, if you could only cause that on a healthy machine on purpose...

12:55 Channeling AvE?

Ah the venerable ZX Spectrum. Single-handedly ruining the eyesight of adolescents up and down the UK 👍