Bad RAM - ZX Spectrum repair

My first proper ZX Spectrum repair. Faulty voltage regulators, transistors and memory get removed and replaced in this very-much-NOT-a-tutorial video.
Guide to tweaking the variable resistors on an issue 2 ZX Spectrum.
spectrumforeveryone.com/techn...
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[@8antipode9]

I'm just here to witness the MASSIVE FINGER BURNS you will no doubt have suffered if you do indeed handle your soldering iron as depicted on the thumbnail of the video.

[@MoreFunMakingIt]

I find it gives me the greatest control if I hold it this way. Also I like the smell of fried bacon 🥓 🤣

[@8antipode9]

@@MoreFunMakingIt Great Job on that white paint BTW. I will try and remember that trick!

[@ctrlaltrees]

Big fan of the TRACO regulators and the "if it ain't broke, don't fix it" approach to the ULA. The gratuituous closeup shots were lovely! Top work as always and great to see another old machine saved from landfill. 👍

[@MoreFunMakingIt]

Love a TRACO! One of those upgrades that just makes total sense. Although they are a bad idea in an Atari 2600 due to interference they can cause. BTW, the closeup shots were done on the usb microscope you featured on your channel! So thanks for that recommendation 😁 And thank you for the kind comments 😊

[@andygozzo72]

personally i wouldnt change a linear 3 terminal regulator for one of those switch mode things just for the sake of it, they dont 'go bad' normally, but if reversed polarity gets shoved in, they die quite definitely !

[@andygozzo72]

i also dont usually blanket recap, in these theres only a couple of critical ones, c46 being the main one, as for replacing/socketing the ula, only replace if bad, heatsink it definitely , socketing it just in case of future failure, making replacement easier/quicker.. depends how good you are at desoldering!

[@andygozzo72]

never 'assume' the dc-dc converter is fixed by replacing those 2 transistors, ..be warned shorted/leaky tr4 and/or bad 4116s can destroy the coil, and vice versa, putting a new tr4 in where the coil is damaged will result in another dud tr4 pretty quickly,, you cannot test for a bad coil by resistance checks as resistance is so low, it fails due to overheating causing a shorted turn or 2 stopping it oscillating it properly .. i'd say tr5 failure unlikely , you can use pretty much any common pnp types for tr5, its only tr4 thats a bit awkward

[@watchmakerful]

@@MoreFunMakingIt Won't these switching regulators send high-frequency noise to the logic circuitry?

[@aaronbuildsa]

I have a terrible memory, so my childhood memories are often vague.. but one thing I vividy remember is being very disappointed when I accidentally peeled up the corner of the metal keyboard overlay and couldn't get it to go back again, somewhere in the 1980s! I've never seen a vice like that before - I'm going to have to seek one out, now :)

[@jackleg693]

Sooooo satisfying to watch and listen to. Excellent work.

[@MoreFunMakingIt]

Perfect! You just made my day 😊 Thank you!

[@RetrogradeScene]

Great job! Thoroughly entertaining and great result!

[@MoreFunMakingIt]

Thanks mate! Glad you enjoyed it 😁

[@brianp7022]

Tip - when removing chips from old boards I cut the legs of the chip first removing it... Then simply heat each pin whilst pulling out.. Yiu can then wick /suck the pad for minimal damage

[@DubiousEngineering]

Great work Lee!! ... thanks for a fantastic education!!

[@MoreFunMakingIt]

Cheers mate! Hope you found something useful 😁 Just shout if you need anything.

[@newbe5]

Cracking video and brilliant editing and BG music! Really satisfying to watch :)

[@MoreFunMakingIt]

Thanks Rich! Look out for my positive thinking series coming soon! 😂

[@leesmithsworkshop]

very nice lee and it's cool to see you pickup tips from so many great people on twitter.

[@MoreFunMakingIt]

I love learning new skills and methods. Wish I'd had the resources available now when I was a kid!

[@leesmithsworkshop]

@@MoreFunMakingIt I know just imagine what we could have done if so much information was free and easy to fine.

[@MoreFunMakingIt]

The world would be a very different place!

[@WhatHoSnorkers]

Lovely work sir, great camera work and explanations too!

[@MoreFunMakingIt]

I'm being binged by a Snorkers! 🤣

[@WhatHoSnorkers]

@@MoreFunMakingIt Ooo-er missus!

[@retrocomputeruser]

Just found your channel with a shout out from Gadget UK164. KZbin's algorithm is terrible at pointing to other peoples videos. Nice work on this issue 2 board but you DO need a scope to get those VR's as accurate as possible for the picture (I think Jan Beta did a video on this) but all the same you got there. I have 10 Spectrum's in my collection including a +3 which all needed repairing. I have also managed to make two replacement modules for all lower RAM and upper RAM which only uses +5V for them to run (similar to JoulsperCoulomb's and Retroleum's design). Looking forward to seeing your future videos on retro computers and have subscribed. 👍 👍

[@MoreFunMakingIt]

Hi Andy! Welcome :) Always expanding my toolset, and not so long ago purchased a scope. Has proved very useful! Working on another ZX Spectrum repair video right now that makes everything else I've seen and done look tame, cant wait to share it. Quite a lot of what I do now has changed from the one you watched, I hope for the better!

[@atarimex2643]

Labor of love….great video!

[@MoreFunMakingIt]

Thank you! Some of the more recent repairs are a bit more involved than this one. Thanks for watching!

[@Bianchi77]

Nice video shot, keep it up, thanks for sharing it with us :)

[@Synthematix]

Heat is what gave these a bad rep, it built up inside until the picture on the screen got distorted. A couple of tips: If you know for sure a chip is bad then just snip off the leads and remove the legs (easier method) Also replace with Nichicon FW series capacitors, these are perfect for computers.

[@piotr.wozniak]

super prepared video

[@FixTechStuff]

You have the opposite problem I do, I'm having more fun making things than fixing things lately! :) Totally agree on buying a broken one.

[@MoreFunMakingIt]

I'll send you my repair videos and you can send me your build stuff. Nobody will notice 🤣

[@FixTechStuff]

@@MoreFunMakingIt 😁

[@draganbodrozic]

Just notice for video mode, electrolytic capacitor is not 100 nano Farad (100nF) but 100 micro Farad (100µF). For cleanup rubber keyboard you can also use moderately warm soapy water and brush. I usually use detergent for hand washing dishes that successfully removes grease and dirt.

[@MoreFunMakingIt]

I'm always getting my farads mixed up! Very much a novice at electronics. Thank you for pointing that out.

[@willyarma_uk]

I fixed my very poorly issue 2 about the same time you did. I had a bad Z80 and bad transistors at the modulator. Only found that out after changing every chip and buying a new ULA! BTW the silk screen on one of the caps is backwards on that board, can't remember which one, its to the right of the upper RAM I think.

[@MoreFunMakingIt]

You got there in the end though! Good work! I'll keep an eye on that cap polarity.

[@StewiesRetroGaming]

Fantastic watch as always buddy. Really thorough how you tackle it and thanks for all the tips included too 🏴󠁧󠁢󠁳󠁣󠁴󠁿😎👌

[@MoreFunMakingIt]

Glad you enjoyed it mate! 😁

[@mopspear]

I like that part where you filled in the words with white

[@TheWisemanwilson]

Really like the video, could i ask the name of the music you have in the background, its really relaxing

[@MoreFunMakingIt]

Hi Christopher! The music is by Sophie Rose. There's a link to her bandcamp in the description 😁

[@tejp5101]

Love your videos Lee. Just assembling my kit for my first 48k mod. Do you test / refurb the original PSUs or do you have a bench supply?

[@MoreFunMakingIt]

Thank you Tej. I use a bench supply for testing. I've not had to repair an original psu yet, but modern ones are fairly easy to pick up or make.

[@tejp5101]

I'm going to wait until I have finished this 48k and a couple of +2s to see if I really want to keep going. Maybe then I'll invest in a bench supply.

[@IlBiggo]

"Increasingly inaccurately named". 4 seconds in and I'm already giggling :D

[@MoreFunMakingIt]

Oh it just gets more silly from here 😆

[@sketter1969]

very good

[@MoreFunMakingIt]

Thank you Marco :)

[@laetitiazichy-vanlidth5882]

Thx from my brother in heaven

[@philbrown1910]

Great to see some trial and error resulting in [spoiler] a fully repaired and refurbished machine!

[@MoreFunMakingIt]

Plenty of error around here! 😂

[@philbrown1910]

@@MoreFunMakingIt 😂 nothing fatal though.

[@markretro3612]

currently got a couple of issue 2's with that damn screen issue, you think you have done it and it comes back when turn your back on it for a second.. the latest one i replaced the trimmers & it worked great then i tried it on another tv and it came back to haunt me (although this particular tv seems to dislike issue 2 species.. very impressed with that font painting ..

[@MoreFunMakingIt]

Thanks Mark 😁 I get the impression that issue 2's need to be tuned to whatever screen is attached to at that time. Bit of a pain!

[@markretro3612]

from what i understand the optimum setting is 50mv/-50mv but from the factory they were set a bit different 120mv / -75mv (off the top of my head, that could be slightly wrong)

[@MoreFunMakingIt]

@@markretro3612 I've since acquired an oscilloscope, so I might revisit this in the future....

[@markretro3612]

@@MoreFunMakingIt i keep looking at them but the ones on my price range will be right at the bottom of the spec list

[@MoreFunMakingIt]

Same here. I picked up an old hitachi to tide me over till I can but something a bit better.

[@firsteerr]

i have a basic knowledge or electronics from my time as a maintenance electrician how would i go about getting the knowledge to repair these old beauties ? i can see that as being a nice little help for me and enthusiasts

[@MoreFunMakingIt]

Exactly the same way I did. Just watch all the KZbin videos and read all the retro electronics repair blogs. Good luck!

[@firsteerr]

@@MoreFunMakingIt ok sounds reasonably sane and logical 😁

[@robs7271]

Hi. What was the diagnostics card you used to find the ram fault. Thanks

[@MoreFunMakingIt]

That was a Dandanator with built in multiply. There are better dedicated diagnostic cards too.

[@RobSComedian]

@@MoreFunMakingIt Great thanks... i'll check it out

[@Montahue]

I just bought a zx 48k. It seems to work ok. I have been able to load magic miner on it. The rubber keyboard looks close to new but smells really bad. Is this a common problem?

[@MoreFunMakingIt]

Not something I've heard of before! Must have had some liquid spilt on the keyboard? You could take it apart and clean it. It is a little risky. Use a hair dryer to loosen the glue on the top metal plate. If it's not coming free it might have brass tabs underneath and you'll have to open the case. Try really hard not to bend the metal face plate. Once that comes off you can remove the rubber keymat and wash it

[@Montahue]

@@MoreFunMakingIt I have taken it apart and and cleaned the the keyboard with soapy water but it still has a very strong chemical smell. But a new keyboard is not expensive:) It is exactly 40 years ago since i last used one of these. Im trying to make it a nice gift for my brother when he is 50 early next year.

[@MoreFunMakingIt]

@@Montahue what a lovely gift! Those rubber keymats are very resilient. Maybe try some more aggressive cleaning agents?

[@Montahue]

@@MoreFunMakingIt Yes, i guess i should try that. The smell is strong, at first i thought it was a really bad tobacco/nicotine smell but it's more"chemical" in nature. I had some experience with bad smelling rubber materials before and thought maybe the smell comes from some chemical reaction in the ageing rubber. I have washed and agitated it with soap water but that did not help. I will let it soak in something stronger and see what happens.

[@damianbutterworth2434]

Hi, I`ve been trying to load games on a 48k speccy for months. Finally got a Arduino type loader. Small 16k games load but not bigger ones. I was suspecting ram and as I was typing this I got a RAMTOP error. So I`ve just answered the question I was going to ask you. If you see this could you tell me which chips I need. I`ve seem some ram for £12 on ebay so might just order that. More fun lol.

[@MoreFunMakingIt]

The upper ram is 4164 dram chips. It might be better to just get an upper ram memory module from Retroleum and replace the whole lot in one go.

[@damianbutterworth2434]

@@MoreFunMakingIt I saw that module. I wonder if it quicker. Anyway I just got 8 4164`s ordered. Thanks for the time in answering. Good channel. I`ve been a sub for a few months.

[@mattcorby]

Apologies if this is a duplicate comment.. not sure what happened to the first one! Method of restoring the logo uses a bit of paper towel: binarysoup.co.uk/2021/04/zx-spectrum-logo-restore.html Didn't think about a pencil rubber, I might try that!

[@MoreFunMakingIt]

KZbin keeps losing comments, it's maddening. Thanks for the link. I'll give that a look! I've had very good results with very dense foam, the kind bath toys are made from.

[@chaoticsystem2211]

Looks like someone cut a live wire with that back pocket wire cutter :D

[@MoreFunMakingIt]

That was a fun day I'll never forget 🤣⚡

[@chaoticsystem2211]

@@MoreFunMakingIt at least you used a proper cutter. not like me, one of the expensive ones...

[@seboc1]

Topnik 🙂 means flux in Polish

[@SpeccyMan]

You are seriously mispronouncing Joules Per Coulomb. 🤣 It is pronounced (phonetically) as Jools Per Cooloooom. 😉

[@MoreFunMakingIt]

Thank you for clearing that up. I have an upcoming spectrum mega repair. I'll try to drop that in there somewhere. I can't guarantee I won't butcher it again. 😂