Sinclair ZX Spectrum Tune Up!
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- čas přidán 11. 07. 2024
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This is the tune up I do to my own ZX Spectrums so they last a long time in top shape:
Chapters:
00:00 Intro
00:52 Replace electrolytic capacitors (and we measure the ones we take out).
11:59 Change keyboard membrane.
16:00 Use a modern voltage regulator.
Anything else major I missed that you recommend? Let me know in the comments!
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Kids today take computers for granted and will NEVER experience the amazement that we did when we unboxed our first home computer. Modern computers are OK, but for learning about the hardware, you can't beat these old machines.
When removing known faulty components from a PCB, you can reduce stress and potential damage to the PCB by first cutting the component from the board with side cutters before attempting to de-solder the leads.
You can then heat the joint with your soldering iron or de-soldering station whilst pulling out the remaining lead using small pliers or side cutters.
We would normally stand the PCB on its end so that we could access both sides of the board during de-soldering.
I learned this technique whilst working for a computer repair company back in the 80's.
Mainly used it on faulty DIL IC's as they are always tricky to get out whole without damaging the traces.
Your radial to axial conversion is awesome, thank you so much. It's great to still learn new tricks after so many years of tinkering with electronics.
I came here to watch a Speccy finding the fountain of youth and left fully satisfied with capacitor yoga. Thanks.
lol
I like your method of folding the radial capacitors Noel. Also I like the way the board looks with the black caps (superficial I know!) Replacing the voltage regulator with a modern efficient item was very satisfying to watch.
One more time : perfect !!! the real class ........ thanks Mister for the knowlege !!! Eric from France
Gran tutorial, gran trabajo!, insuperable.
Great video and great channel, I'm re capping all of my Speccy's at the moment.
Thanks! Glad you liked it. And watch out for the polarity in some of the caps! Remember that some boards have them backwards.
Muy didáctico y bien explicado. I enjoyed the video very much!!
I love those new regulators, I've put them in all my 48K's. Just need to get some 2amp versions for my 128K Speccy's.
i measure old capacitors too.... lol when i replace them .... exellent job!!!!!
Fantastic!
The first axial replacement on the board had solder holes for radial capacitor leads. There was no need for all of that fancy lead bending.
Failing capacitors, especially electrolytics begin to electrically leak. This means they are turning into resistors. They begin to allow DC to leak through. Eventually they can turn into a dead short. This is why you change old capacitors.
ESR meters do not check for DC resistance (parallel resistance). ESR is only equivalent series AC resistance. However, electrically leaking capacitors can throw off an ESR measurement.
Great video Noel!! My original ZX Spectrum 48k isn’t working anymore, so I’ll have to dig a bit more if I try to fix it, but I have a second one that a friend of mine donated to me years ago, to which I can try all your suggestions!!
I was doing the same thing when I was soldering components on the board and I think that it is more correct to cut the long leads first and then solder them. Because when they produce the boards, they dip the whole side of it in a solder "bath", thus covering all of the trimmed leads. But when you clip the leads after you solder them, you expose the copper in moisture and other corroding factors, like capacitors' oils. As well as battery fluids, on newer computers.
And as for the DC to DC converters, I have heard that they produce a lot of ripple on their output. I haven' t used any, but I watched a video, some years ago.
I've heard that argument multiple times but I need to research it before I'm totally sold. It does make soldering slower and more annoying, so I want to make sure it's worth it before I switch 😃
That voltage regulator is really good. At least in my set ups, I don't see any kind of visual noise at all. I can highly recommend it.
Cutting the leads before soldering is to prevent oxidation of the exposed copper where it's been cut. That of course implies a complete tinning of the remaining wire right up to the cut.
That's what i learned many Years ago.
@@christiankolliker9006 you must have learned how to fix TVs in Switzerland then. Or some related profession.
@@matthiasmartin1975 The company in which i did my Qualification was producing Blood Analyzers and after this Company got bankrupt i finished at the Federal Institute of Metrology
@@christiankolliker9006 Wait, you did your apprenticeship at Theranos? ;-) JK
@@matthiasmartin1975 No, it was Greiner Electronics.
I am about to make a "First power up" video for my 48k that I recently got on Ebay. I had an idea to short the 7805 and power my Spectrum from an external 5v source. Then I looked at the schematic, and it turns out 9v is used to power the voltage inverter... Darn it! As the brits would say. :) I guess it's still feasible if we replace 4064 DRAM chips by 4164 which use 5v only, but that's a lot to do. And because I actually do have experience with the 4064s, I can say they are very sensitive to voltage, if you power them without -5v, they may fail instantly.
Right. Yeah, all the models until the 128K need those weird voltages. But converting 4164 to work as 4116s is actually really easy. And coincidentally, today's video deals with that exactly (coming up in about an hour), so maybe have a look at that.
The colour encoder ic needs 12v as well.
Great video Noel. Thanks!
About the electrolytic caps: I have recapped several mid to late '70's stereo amplifiers (so literally dozens and dozens of capacitors, probably hundreds in all) and have yet to find one single electrolytic which was anywhere near being out of tolerance. What would the ratio of bad caps you have come across in the Spectrum's that you have refurbished?
Hi there, great channel, well made informative videos. I did the same voltage regulator mod to one of my Spectrums but found the case did not close properly afterwards, I had to lay the new component down and solder short stiff wires to it to get the lid to sit down properly.
Thanks! That's weird. Maybe you used a TRACO model that has higher current rating (which is good) but that's a bit larger? The one I was using fits right in without a problem.
Excellent video. Is the replacement composite video out covered here or elsewhere? Thanks
Thanks! I have a whole other video dedicated to the composite mod: czcams.com/video/IocU4fEHAF4/video.html
¡Mola la camiseta! Es del Knight Lore ¿verdad?
Sí, por supuesto! :-)
Nice solution of radial to axial. I think at C25 you overkilled it since at the neg point there's both hole for a radial. so you just stand it up normally the radial there.
Hi there. Great channel... I'm almost about going to my parents basement search for my 2+. One question about the power regulator. The 7805 is a linear regulator and I think the TSR 1-2450 is a switching regulator, right? Doesn't the noise produced by the switching reg cause any issues with the clock or any other noise on the power lines?
Correct on both counts. This particular one doesn't introduce any noise that I noticed. Certainly not in the functioning of the system. Maybe in some displays it'll introduce some noise in the video signal? Not sure. For my set up it works great.
I should fix up mine sometime soon. It stopped working when I was a kid and was playing Starquake and then I bought a second hand C64 instead! For some reason I removed the power socket back then, even though that's probably not what the problem was. Also I appear to have removed some of the pads where the socket legs go in (must have torn it off badly) and so that will present problems, let alone diagnosing the original fault. At least the keyboard membrane seems intact. Also I no longer have the power supply but I bet there must be decent modern replacements.
I feel like I owe it to my kid self to repair this, maybe before the 40th anniversary of me getting it (my first computer) :-o
The good news: If it's just the power socket pads, that's not a problem if they're ripped. You can fix that with a couple of cables.
For PSU, any 9V DC jack will do but it has to be CENTER NEGATIVE. If you can't open it and swap the polarity, you can just cut the wire, flip the wires, and resolder it.
The bad news: The keyboard membrane is most likely dead.
Let me know how it goes!
@@NoelsRetroLab OK thanks for the tips!
Were any caps faulty? I would expect late 70s blue ones would outlast new fitted caps
It's amazing how a modern voltage regulator can do the same job as the original one without generating all the heat. Can the same mod be done to a toast-rack? Can the actual toast-rack heatsink be removed afterwards?
Absolutely! Although with the toastrack it's not nearly as necessary because it has such a good heat dissipation.
FIrst Cap: Why haven't you used the via right next to the negative hole/pad?
Interesting. The main reason is that I didn't think about it 😃 Second is that I was trying to keep the same vias as the original capacitors, so I wasn't even looking for alternatives.
I'd expect to see some glue residue on the plastic below the keyboard metal plate. This way it seems like it had already been cleaned up at some point.
It could be. It also depends a lot on how the glue dries out. Sometimes it's super sticky and sometimes it's a lot more dry like that. Maybe it depends on how hot the Spectrum got (or how much it was used).
Hi sir, i'm from greece, i have one 48k , how can i found ula, membran ... Such as spare parts,,Ebay and others ..i cant trust for them, how can i buy directly and i wish to pay with my credit card, best regards..
you can make a cool mod, output sound to tv, like de tk90x we have in Argentina.
True, that would be a fun little mod!
Hi. What's the difference between the TSR 1-2450 and the TSR 1-2450E? In the datasheets, the only difference I spotted was a 0.5V difference in the input Voltage.
Also, any suggestions where to buy them? In the US they are ~$3.00 but over here in the EU these things are ridiculously expensive (at least in my local shop).
The cheapest source I found was Mouser, but you need to place a 50€ order to get free shipping, so that's not always possible. Not sure about the exact difference there. Usually the numbers indicate the maximum rated amps, so some of them can go to 1.5A or 2A, although that gets even more expensive.
I'm on my way changing all capacitors on my spectrum to get a readable image quality.
Where could I find a spec of the capacitors I need?
You could just open it up and look at the existing capacitors. You should choose ones with the same capacitance and same or higher voltage rating. Or, if you know your board issue, you can just check here: spectrumforeveryone.com/technical/capacitor-lists-48k-range/ Good luck!
I have a C64 with an old 326298 board that has a UA7805UC which gets very hot. Could it be replaced by a traco power TSR 1-2450?
I think so. The thing is to make sure the voltage regulator can provide the same current. The AU7805UC seems to be rated at 1A, so that should be fine. However... it's possible that the TRACO Power could introduce some noise. I haven't tested it on a C64, but it's worth a shot. If not, it's easy enough to change back.
How did you find a new membrane? Are they still made?
Yes, people are still making them. You can find them in sellmyretro for example.
linear voltage regulator gets hot but delivers clean volts. I think the one you put in is pwm based and not give as clean volts.
in audio products then you must always use linear regulator!
True. These are fine for this particular application, but I can see them not being OK in sensitive audio applications.
There arem more noise from the mainboard, it runs very fine. If you have some problems with noise, put an L-C filter after the regulator.
My original +3 works (except the disc drive) but it’s real blurry on screen. I take it the steps in this video for the rubber speccy would be similar?
The +3 doesn't usually have really bad capacitors because it doesn't get as hot. In any case, those would be inside the external power supply. Is it blurry when you use the RGB cable, or just the RF? I would start looking at that. But the +3 with an RGB cable should be super crisp (if anything, almost too crisp and you get some weird vertical bars).
That’s good to know, thanks. It was very blurry. It’s in storage atm so I’ll get it back out and give it another try see what cables I’m using etc as I’m not at all technically minded XD
There was an old NASA soldering guide, IIRC, that said the procedure was to cut the lead before. See NASA-STD-8739.3 "Lead Bending and Cutting", but might not be the guide I remember.
Yes, I've seen that recommended from time to time. I don't doubt it's better form, but it's usually much more of a pain to solder components that are just the right length. I try to cut the lead away from the solder joint, so hopefully that's good enough.
@@NoelsRetroLab I learned that the reason to cut first, is to avoid exposing a little bit of bare copper. Copper is more susceptible to corrosion than solder, so you want it tinned.
@@NoelsRetroLab The NASA specs stuff is just more "I heard it on the internet..." stuff that doesn't apply to recapping old computers, unless you plan on launching it to Mars.
They clip (and tin!) leads before placement because some sensitive components may be damaged, but more so because you don't really want someone damaging something else while trimming the leads. They also like pushing the leads flat onto the PCB, stops them shaking loose. Makes it hard to service, but it's a bit hard to do that once it's in orbit anyway.
You don't need to trim the leads before wave soldering, they slide the finished boards over a saw to cut the excess off. Seriously.
The corrosion thing really doesn't happen, I think NASA conformally coat everything anyway.
That said, if you're making something to go on a car or motorbike, give their guides a read. Vibration really kills boards.
Where do you buy those membranes?
I believe I bought them through sellmyretro. I think these came from RWAP. They're great!
@@NoelsRetroLab incredible this stuff still is for sale.
@@defdac No, no, those aren't original membranes. These are membranes that people have designed and manufactured recently to fit in these computers. It's really cool that people are doing stuff like that. Otherwise old computers would eventually become unusable for one thing or another.
Kandungan anda sangat menyentuh
Why not add composite out at the same time?
Few modern TV-sets (none?) supports RF-signals any more.
Yes, it's perfectly fine to do it at the same time. I did it in a different video (look in the ZX Spectrum playlist if you're interested), so I didn't want to repeat it here.
A little insulation from some wire on those cap leads is never a bad idea either.
You know, I started doing it that way years ago, but it adds a lot of work for a very minor improvement so I gave up. Is the idea that if the capacitor covering ever wears out that it won't short, or is it to prevent accidental shorts with something from the top?
@@NoelsRetroLab Fair enough... but for both reasons you asked, it's just another safe-guard to protect your precious and hard to replace retro. Just a good habit to get into. What I would do is by a small spool of solid wire at a reasonably heavy gauge and gut 6 inch pieces off and strip the insulation off one side and the other side usually pulls right off. Then I keep those around and cut to size as needed, this way you have them ready. Not to mention it looks more professional.
Some heatshrink would do the job
Heatsink the ULA.
That's probably a good idea but I haven't done it before. I imagine the ULA needs to be un-socketed to fit the heat sinks, right? I should try some day.
@@NoelsRetroLab No need to remove the ULA from the board, you can get small heatsinks and thermal adhesive, that's what I do to all my speccys :)
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@@drgusman put a thin metal plate , with heatsinkglue on the ULA
Please spend the extra 5p on axial caps...
It's not so much about spending the extra money, it's about not waiting weeks for them to arrive. And since I have radial ones already, that's what I end up doing.
@@NoelsRetroLab isn't there a good chance you're gonna make the outside metal case of the cap live? Will that not potentially be an issue?
You enjoy fixing computers...you work for other people fixing computers??
No, this is my hobby. I'm a game developer professionally, so I suppose this is not THAT far from that 😃
zx spectrum 80, 81,82 has to be the worst computer ever made.