ZX Spectrum Issue 2 Repair and Restoration

[@delsydsoftware]

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.

[@pqrstzxerty1296]

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

[@1337Shockwav3]

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).

[@JanBeta]

Oh, didn't know that. I'm still a noob concerning the Spectrum world. I will look into that. Thanks for adding! :)

[@SirWolfCZ]

The 4164 DRAMs can't be used directly, they need to be modified: pin 8 lifted and connected to pin 9 and maybe pin 1 snipped off.

[@cjmillsnun]

@@SirWolfCZ or the 12V and -5v tracks on the board cut, with the 5V then bridged onto the old 12V rail. This will give the same without cutting chips and is reversible with a couple of bodge wires on the board.

[@timstah8450]

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!

[@JanBeta]

Ah, glad I could help. Retroleum is my go-to place to buy spare parts since I found it. Very fast shipping, too.

[@MindFlareRetro]

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!

[@JanBeta]

Thanks! Yes, it turned out to be a lot easier than I thought with the diagnostics software. :)

[@netuser3905]

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 ?

[@chris-ip4pk]

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

[@Imperious685]

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.

[@JanBeta]

Thanks. :) I went for keeping the looks of it because it was loved so much by the previous owner and you I like how it kind of tells a story. I have another speccy that looks near mint so I can always choose between this battered one and the clean one.

[@michaelm7256]

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

[@JanBeta]

I wouldn't recommend spiritus. It has enough alcohol in it for cleaning but the rest of it is filled up with random chemicals that could potentially be conductive/cause reactions with plastics. It will probably work for most stuff but I wouldn't use it for anything I care about.

[@xorben1981]

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

[@JanBeta]

Glad you liked it. Yeah, the Speccy wasn't very common here at all. Lovely little machines still. :)

[@vladeb1104]

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

[@JanBeta]

Yeah, I spend a lot of time lurking in forums and researching things. I sometimes am surprised that the tools I use are not known by many people.

[@GadgetUK164]

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?

[@JanBeta]

Thanks! You have to click "here" in the "Introduction" section. Admittedly it's a bit hidden in there... I added a direct link in the description. -> github.com/brendanalford/zx-diagnostics/releases/download/v0.35/Release-v0.35.zip

[@GadgetUK164]

Much appreciated =D

[@bennyalford]

I highly recommend reading the wiki if you're unsure of how to get started :) github.com/brendanalford/zx-diagnostics/wiki

[@martin-ot]

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

[@vopnihauksson5806]

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

[@pqrstzxerty1296]

ipa

[@ChrisWhiteTech]

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

[@ChrisWhiteTech]

Or maybe changing some caps,and if yes,wich of them? Thank you

[@JanBeta]

I also get color dots crawling and flickering. I think the picture looks better in the video than it does in real life actually. Replacing all the electrolytic caps on the board makes sense and improves the picture a bit but generally the output from these old Speccys is not very good unfortunately. :/

[@ChrisWhiteTech]

Ah,ok, i thought only i have the "dirty" image, it's funny you say that in real life has flickering, i will leave it be,then, and i must say in this vid, the picture looks allmost flawless! Frustrating, actually :)

[@sarreqteryx]

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

[@JanBeta]

It is the so-called "spider mod" which made up for some I/O issues with the ULA chips used in the issue 2 speccys. If I understood it correctly, they tried fixing issues that the early ULAs (used in issue one boards) had and overdid it so they had to make this mod to compensate.

[@Hagledesperado]

12:55 Channeling AvE?

[@JanBeta]

I watched far too many of his videos, I guess. ;)

[@Hagledesperado]

He's hilarious. I find your videos more interesting though.

[@JanBeta]

He is indeed. I can't watch too many of his vids at a time though. Glad you find my stuff more interesting. I'm honored. :)

[@DaveDoc1984]

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.

[@GadgetUK164]

The Famicom composite output is too low - you can (to test) just connect the video output pin on the PPU straight to your composite lead but it will be quite dark. I showed how to AV mod these in the 5 famicom repairs videos - its not hard, remove several components, swap a few resistors etc.

[@DaveDoc1984]

You sure did. I will have a look at that. This particular Famicom I was going to restore and put it in the Box I have which came with my other NESRGB Modded Famicom. Just wanted to keep one standard but will need to do some form of mod so I can see the video output, when I know I have fixed it I can reverse the mod. The issue with the one I have picked up appears to be a faulty SRAM as one of them gets BELTING hot after only 1 minute or so of being switch on.

[@RichSzerman]

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

[@Archimedes75009]

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.

[@JanBeta]

Send me an email! The address is on the "channel info" page. :)

[@Audiosonicity]

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

[@JanBeta]

Thanks! I will keep an eye on C46. Recapping and heatsinking is next on the list.

[@TheHighlander71]

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.

[@JanBeta]

That's definitely on my to-do list. The caps in these old Speccys are not of very good quality. The only reason I didn't do it right away is that I didn't have enough spare caps.

[@TheHighlander71]

Yeah and some of them are axial caps. I bought a complete set off JoulesToCoulomb a long time ago.

[@JanBeta]

Yes, all axial caps in this one. It's not so easy to get them in reasonable quality. Probably going to order a set off Retroleum. I'll also check if JoulesPerCoulomb still sells them.

[@TheHighlander71]

JoulesPerCoulomb..that was it.

[@MarkTheMorose]

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!

[@JanBeta]

Mostly due to the fact that I didn't sort stuff on the SD card I'm using yet and Boulder Dash was conveniently located in the main folder. ;)

[@DAZZYVANDAM]

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!

[@JanBeta]

+DAZZYVANDAM RETRO GAMING Thanks! Yeah, retro computers where built to last a bit. At least they are much easier serviceable than most modern stuff. ;)

[@Markchill2]

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

[@JanBeta]

Yes, that's probably the best way to do it. :)

[@chewabledrapery]

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 :(

[@JanBeta]

Yes, it can be quite a pain to work on these. I suppose they left out sockets to further cut the cost back in the day. Sounds like a RAM or ULA issue you have there (but obviously difficult to tell from a distance). Hope you can fix it!

[@chewabledrapery]

@@JanBeta yeah going to save up for a desoldering rig and then socket the board, I've needed one for 30 odds years so now is the time to invest I reckon, appreciate the reply Jan I love watching your videos, keep up the good work 👍

[@TEBLify]

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 :-)

[@JanBeta]

Oh, glad to help. :)

[@anestiskoutsoudis2830]

Μπράβο. Ωραίος οδηγός

[@Archimedes75009]

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

[@JanBeta]

I became short-sighted because I used an old black and white TV as my first monitor on my C64. ;)

[@Archimedes75009]

I had the B and W TV for the ZX80 and possibly 81, and got colour when the Speccy became a member of the family. Spent so many hours playing, typing BASIC progs, and duplicating tapes to the microdrive and then the Beta Disk ... That got my eyesight ! Fortunately laser corrected it. Thanks for your vid. I am considering funding you a bit, possibly starting in October when my purse allows it.

[@JanBeta]

I spent hours and days on the C64. Didn't have a color monitor until the mid 90s on the Amiga. Wearing glasses/contact lenses now. Totally worth it though. ;) Thanks for even considering funding me. :)

[@mvl71]

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

[@TheDefpom]

You should probably recap it too.

[@JanBeta]

Yes! That's definitely on my list. The caps in the old Speccys are not very good quality. I didn't do it because I wanted to get fitting axial caps first.

[@netusernetuser8457]

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

[@philoffhistree]

very nice thanks for the links

[@CyberhugTechnologies]

great job...again ;-)

[@patrick-leekelly7681]

Good 👍 job

[@factorylad5071]

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

[@NotMarkKnopfler]

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

[@sma7530]

Only if you play Sam Fox's Strip Poker 😉