Sinclair ZX Spectrum 48k | Charity Repair and Refurb
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- Опубликовано: 5 июл 2024
- In this video I refurbish a Spectrum 48K computer that was found in my neighbours loft. I ran some tests using a diagnostic ROM and I found a memory fault, which I repaired along the way.
I'm selling this Spectrum on eBay (as December 2020) in aid of a charity.
Chapters
0:00 Intro and machine condition
1:48 Pre-power checks
4:49 Powering up and memory test
5:50 DC to DC convertor
7:29 ULA heatsink
8:44 RAM replacement
10:41 Re-capping the board
11:40 Video mod
13:39 Case and keyboard repair
16:45 Final test and games 
Наука
I would have added a RESET button on the back as we all know that the main damage done to spectrums was removing the Power Plug as it often broke
I think you can buy DC leads that have a switch in them, to save wear and tear on the power connector.
@@RetroWorkshop i was going to say that
Great restoration video, I had a Speccy myself back in the 80's. The only thing I can't get is why there are only 100 likes or so for this video, go figure.
Very nicely done!
Fab video. Nice and clear. Good work!
Thanks Chris!
Great video mate all for a good charity
Really enjoyed this. Thanks.
Amazing job. Bravo.
In this video I refurbish a Spectrum 48K computer that was found in my neighbours loft. I ran some tests using a diagnostic ROM and I found a memory fault, which I repaired along the way.
I sold this Spectrum on eBay in December 2020 for £83, and the full amount was donated to charity.
Further details on this repair can be found on my website: www.retroworkshop.uk/sinclair-zx-spectrum-48k-charity-repair/
Awesome job!
Nice. Would love a zx spectrum 48k + again.
Amazing video. :)
With a capacitor on the TV it turned out well.
good job!
Brilliant thankyou
Great restoration work! If one of the buttons like Load is not working, is it just possible to fix by changing old membrane to new one?
Highly likely a new membrane would fix that.
@@RetroWorkshop Thanks for info!
He’s alive!
Yes I’m back with another Sinclair repair video. Hope all is well down under.
@@RetroWorkshop Got links to the eBay auction? You still on Twitter?
www.ebay.co.uk/itm/Fully-refurbished-Sinclair-ZX-Spectrum-48k-with-new-PSU/333816096002?hash=item4db8fd6502:g:aDkAAOSwIK5fzOAQ
Excellent content as usual .
May I ask what were the replacement transistors you used to increase the brightness after the video signal output mod?
Information can be found here: www.retroworkshop.uk/sinclair-zx-spectrum-48k-charity-repair/
@@RetroWorkshop Thank you kindly.
"Replace TR1 and TR2 with BC549C" Inserted the opposite way around.
👍👌
Given the regulator takes 9V and drops it to 5V, if it was fed 6V would it dump less heat? I'm guessing Sinclair used 9v supply because that such PSUs were cheap and plentiful. Or are there are elements on the board that need 9V?
Yes a lower voltage before the regulator would produce less heat. The original PSU was unregulated. Therefore it may provide more or less voltage, depending on the load. Nowadays we’re used to more complex (but now cheap to manufacture) regulated PSUs that output a constant voltage. Not sure I’d go as low as 6 but certainly 7 volts would work. The input voltage probably does come out of the rear expansion but I’m unsure if any devices make use of it.
@@RetroWorkshop thanks. So a modern PSU is probably a good idea to increase Spectrum lifespan if one isn't into opening it up and getting the soldering iron out.
Great repairing video...I find it on time. Can you share the characteristics of that DC -DC converter? Maybe a link.
It is a murata convertor from retroleum.co.uk
@@RetroWorkshop I did the mode you showed for the composite signal and the image flickers every 3-4 seconds. Do you have an idea why that happens?
btw the transistors you used to bring brightness up were the same (new parts) or a different variant?
@@nickolasgaspar9660 Have you got the capacitor the correct way round? Have you replaced the two transistors? Noting that they are different transistor types and have to be inserted the opposite way round - "Replace TR1 and TR2 with BC549C Inserted the opposite way around"
Can I write this test ROM on chip and desolder original for replece and test? Wich was a new TR1 and TR2 Instead of ZTX 313? wich polarity for cap on RF-modulator? Thanks
It is a lot of work to desolder the ROM. The SMARTcard (and other similar devices) allow you to take over the on-board ROM using the device that plugs into the expansion port. You can also copy alternative ROM images and boot from them. Details of the ROM I used are here: www.retroleum.co.uk/diagrom/diagrom.pdf
There is another popular test ROM by Brendan Alford here: github.com/brendanalford/zx-diagnostics/wiki/Firmware
I think I have seen people use one of these burnt into a ROM in the original Spectrum, but I can't be certain.
For info on the capacitor mod see here:
blog.retroleum.co.uk/electronics-articles/repairing-a-zx-spectrum/spectrum-video-mods/
For details on the replacement transistor for higher level video output:
www.retroworkshop.uk/sinclair-zx-spectrum-48k-charity-repair/
maybe the screwdriver wasnt the best tool to use imo 🙄but great to see you do your thing👍
Hello, could you give me a purchase link for this DC DC converter, where did you buy it or on Aliexpress that is economical? I also wanted to know where to buy a DC power input connector for a zx spectrum 48k. Thank you
Hello, Retroleum.co.uk is where I bought the DC to DC convertor (it is their MuRata Switch Mode 5v Regulator (replaces 7805)). They also sell the DC connector you want (Replacement 2.1mm DC Power Socket).
@@RetroWorkshop Thank you!, I also need a low dram 4116 memory for the IC13 bank, do you know where I can buy it that is economically cheap.
good afternoon, i have a spectrum i already removed the low memories and i have the c49 boiling what could it be? thank you
No idea.
What clamp do you use to hold the board?
It is a Duratool PCB holder, from eBay.
Perhaps replacing old caps for new may not always be such a good thing.... The quality of electrolytics these days maybe worse ("cheaper & designed to last only to fulfill the warranty period") than it was then, however today's tech is expected to be better. Would be interesting to do a mass sample of new and old.
I am normally a bit skeptical about replacing electrolytics en-mass, just for the sake of it. I prefer to measure with an ESR meter to judge health, and replace as necessary. However, in the Spectrum, it appears to be worthwhile. I've got another video where I looked at two machines, and the picture quality was improved by simply replacing the caps, even though the ESR was worse in the newer caps. There are clearly other factors at play (leakage etc.).
"I've previously restored a couple of ... spectra?" 🙂
chuckie egg !!
was the spectrum made in England or China ?
The original machines were assembled in Dundee in Scotland. Later machines were built by Samsung in Korea. The +2 and +3 machines that were built once Amstrad had bought the rights to the Sinclair ZX Spectrum range were built in Taiwan;
LASER Computer
Direct soldering of chips is VERY dangerous. Heat from the soldering gun can easily destroy the chip. That's why sockets are used. If you get no problem then you are lucky. It's playing with fire in more ways than one.
Understood that undertaking such work risks damaging the chip or the PCB. I am quite experienced with such repairs so was happy to undertake this work. As these devices run hot (very hot in the case of the older series ULAs) this mod is recommended to extend the life of the ULA. It was suggested by Mutant Caterpillar I think, who is very experienced in Spectrum repair.
I have desoldered (and many others) numerous of chips from all types of boards..... Ataris, C64 , Spectrums, Amigas etc. If a chip can survive a desoldering process then soldering a chip ( a far less heat intense process) can never be that dangerous....
Seeing you do solder work, I was specifically told, not to do, what you are doing which is touching the electronic components with the soldering iron. The best way is to touch the electronic components with the solder wire, then touch the solder wire with the iron.
Never heard that Ronnie, and never had any issues. The main guidance I was trained with, is the two second rule, regarding max time to leave the iron on the pad. From experience, the weak point is the pad on the board.
Aha!! I may need to borrow your smart card - I have a spectrum with a problem :-). Can we chat please?!?
This is probably the best and most detailed refurb I’ve seen!! Great video!!!