Any thoughts on what kind of internal RAM upgrade this might be?

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twoangrybears
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Joined: Fri May 17, 2019 3:29 pm

Any thoughts on what kind of internal RAM upgrade this might be?

Post by twoangrybears » Thu Jul 25, 2019 8:15 pm

Hi everyone

I've opened up a ZX81 I bought as not working on eBay and found the following user modification to the RAM.
Front.png
Back.png
I am assuming that the original owner has (tried to) upgrade the internal RAM but I cannot see how the modifications that they have made correspond to the internal RAM upgrades I have read about elsewhere.

Does anyone have any ideas as to what kind of RAM upgrade this might be and whether or not it looks like it should work. From what I've read it looks as if some of the pins should have been bent up but I am just guessing.

It is possible that this is a botched upgrade and that this is the reason why the machine does not work. I don't know. I don't even know for certain that the machine does not work as I have not applied power yet or made any other tests. I wanted to inspect visually to see if there were any obvious issues with the motherboard before I did so and found this which baffles me (but being new to this, many things baffle me so I thought it wisest to ask!).

Thanks in advance for any suggestions.

(I took these photos earlier and am not in front of the machine right now so I'll have to take any suggestions in batches and do them all at once when I next get time to sit down to do so. I will update this thread with any new information as and when I get a chance to investigate further.)

Lardo Boffin
Posts: 1006
Joined: Sat Nov 26, 2016 2:42 am

Re: Any thoughts on what kind of internal RAM upgrade this might be?

Post by Lardo Boffin » Thu Jul 25, 2019 9:23 pm

It looks underneath like this one I have done myself a good few times:

http://8and16bit.blogspot.com/2015/08/m ... o.html?m=0

Not sure about the wire on top though - maybe a track got lifted and that is a repair?
ZX80
ZX81 iss 1 (bugged ROM, kludge fix, normal, rebuilt)
Iss 3 ZXVid
TS 1000 iss 3, ZXPand AY, ZX8-CCB, ZX-KDLX & ChromaSCART
TS 1500
TS 2000
Spectrum 16k (iss 1 s/n 1499)
Various Spectrum 48ks plus a DIVMMC future and SPECTRA

Lardo Boffin
Posts: 1006
Joined: Sat Nov 26, 2016 2:42 am

Re: Any thoughts on what kind of internal RAM upgrade this might be?

Post by Lardo Boffin » Thu Jul 25, 2019 9:25 pm

Actually I can see that it is a fixed track - see below.

E6613CCD-E173-45D1-A5B0-276794506CA4.jpeg
ZX80
ZX81 iss 1 (bugged ROM, kludge fix, normal, rebuilt)
Iss 3 ZXVid
TS 1000 iss 3, ZXPand AY, ZX8-CCB, ZX-KDLX & ChromaSCART
TS 1500
TS 2000
Spectrum 16k (iss 1 s/n 1499)
Various Spectrum 48ks plus a DIVMMC future and SPECTRA

Lardo Boffin
Posts: 1006
Joined: Sat Nov 26, 2016 2:42 am

Re: Any thoughts on what kind of internal RAM upgrade this might be?

Post by Lardo Boffin » Thu Jul 25, 2019 9:27 pm

Not sure about these:

0F5CD564-4695-4654-8D31-0B5F4DBB05F7.jpeg

Maybe more fixes?
ZX80
ZX81 iss 1 (bugged ROM, kludge fix, normal, rebuilt)
Iss 3 ZXVid
TS 1000 iss 3, ZXPand AY, ZX8-CCB, ZX-KDLX & ChromaSCART
TS 1500
TS 2000
Spectrum 16k (iss 1 s/n 1499)
Various Spectrum 48ks plus a DIVMMC future and SPECTRA

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twoangrybears
Posts: 4
Joined: Fri May 17, 2019 3:29 pm

Re: Any thoughts on what kind of internal RAM upgrade this might be?

Post by twoangrybears » Thu Jul 25, 2019 9:47 pm

Hi Lardo

Thank you. That is amazingly helpful. Is the site you link to yours? Those pictures are very useful.

Next time I get a chance to sit down with it, I am going to risk powering it on and then, if there is no display, start investigating further. Now that I know what this mod is supposed to be doing, I'll have a better chance of working out if it is working as intended.

I'll keep you posted on my progress.

(And thank you for your welcome on the other thread too!)

Lardo Boffin
Posts: 1006
Joined: Sat Nov 26, 2016 2:42 am

Re: Any thoughts on what kind of internal RAM upgrade this might be?

Post by Lardo Boffin » Thu Jul 25, 2019 11:10 pm

twoangrybears wrote:
Thu Jul 25, 2019 9:47 pm
Hi Lardo

Thank you. That is amazingly helpful. Is the site you link to yours? Those pictures are very useful.

Next time I get a chance to sit down with it, I am going to risk powering it on and then, if there is no display, start investigating further. Now that I know what this mod is supposed to be doing, I'll have a better chance of working out if it is working as intended.

I'll keep you posted on my progress.

(And thank you for your welcome on the other thread too!)
You are welcome! No the site isn’t mine. I am ok at following other peoples instructions and expertise but not in coming up with ways to do these things! I am also familiar with lifted tracks when modding these things. :oops:
ZX80
ZX81 iss 1 (bugged ROM, kludge fix, normal, rebuilt)
Iss 3 ZXVid
TS 1000 iss 3, ZXPand AY, ZX8-CCB, ZX-KDLX & ChromaSCART
TS 1500
TS 2000
Spectrum 16k (iss 1 s/n 1499)
Various Spectrum 48ks plus a DIVMMC future and SPECTRA

Lardo Boffin
Posts: 1006
Joined: Sat Nov 26, 2016 2:42 am

Re: Any thoughts on what kind of internal RAM upgrade this might be?

Post by Lardo Boffin » Thu Jul 25, 2019 11:14 pm

Has it been composite modded? Daft as it sounds I sold one (of quite a few) on eBay where I had done the RAM as shown and fitted a ZX8-CCB composite mod board and the buyer got in touch to say it didn’t work. He had tried to plug it into the RF input of the telly and not a composite socket! :) Once plugged into the correct socket all was well.
After that I always bundled a composite to SCART adaptor with them to be sure it was plugged in correctly. 8-)
ZX80
ZX81 iss 1 (bugged ROM, kludge fix, normal, rebuilt)
Iss 3 ZXVid
TS 1000 iss 3, ZXPand AY, ZX8-CCB, ZX-KDLX & ChromaSCART
TS 1500
TS 2000
Spectrum 16k (iss 1 s/n 1499)
Various Spectrum 48ks plus a DIVMMC future and SPECTRA

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1024MAK
Posts: 2434
Joined: Mon Sep 26, 2011 10:56 am
Location: Looking forward to summer in Somerset, UK...

Re: Any thoughts on what kind of internal RAM upgrade this might be?

Post by 1024MAK » Fri Jul 26, 2019 12:35 am

twoangrybears wrote:
Thu Jul 25, 2019 9:47 pm
Hi Lardo

Thank you. That is amazingly helpful. Is the site you link to yours? Those pictures are very useful.
That be my blog. I really must get around to posting up some more content. But real life and distractions keep consuming my time...

Mark

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