Identifying Board Version

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albertusj
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Identifying Board Version

Post by albertusj » Sat Jul 13, 2019 12:17 pm

Is there a way to identify the board version of a ZX Spectrum that doesn't involve having to open it?

It has a yellow 48K sticker underneath and serial number: 035-202763 in red by the expansion port.

PCB is green and the keyboard membrane cable is dull transparent white.

I can also see the heatsink. It is folded such that it is just above the edge connector. I can see the reflections of the chips below it.
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"It is often possible to determine which version of the Spectrum 16/48K one has without opening the case, as there are a number of clues:

If the rubber keys are a light fawn colour it's an issue 1 board.
If the keys are dark grey, look into the edge connector slot to see whether an aluminium heatsink is visible -especially at the power socket end. If you don't see the heatsink it's an issue 2 board which has the heatsink near the forward corner of the board, under the keyboard.
If the heatsink is visible it's an issue 3 or 3B board - there is very little difference between them.
Although the Spectrum+ usually has an issue 3B board, this cannot always be assumed - the Spectrum+ keyboard upgrade kit allowed owners of older machines to house their old circuit boards in new cases." - Planet Sinclair
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ZX80/ZX81/ZX Spectrum

Lardo Boffin
Posts: 1015
Joined: Sat Nov 26, 2016 2:42 am

Re: Identifying Board Version

Post by Lardo Boffin » Sat Jul 13, 2019 3:22 pm

If you google images of the PCB versions (list here https://spectrumforeveryone.com/technic ... um-models/) and then compare what you can see through the edge connector to what you can see in the images you can probably identify it.

There are quite a few images here https://k1.spdns.de/Vintage/Sinclair/82 ... ogonal%29/
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
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Re: Identifying Board Version

Post by 1024MAK » Sat Jul 13, 2019 4:31 pm

The position of the heatsink only tells you if it is an issue 1 or issue 2 (not above the edge-connector) or is an issue 3 or later.
Issue 5 and issue 6A boards use a second 40 pin glue chip instead of smaller 74LSxxx chips to control the “upper” 32K RAM, these are visible so you can distinguish between:
  • Issue 1 - heatsink NOT above the edge-connector, one of the DIL sockets for the 32K RAM extension board visible near the power socket (assuming this board is not actually fitted).
  • Issue 2 - heatsink NOT above the edge-connector,, ROM and Z80 very close to the edge-connector.
  • Issue 3, issue 3B, issue 4A, issue 4B - heatsink easily visible above the edge-connector, only two 0.6” chips visible from the edge-connector.
  • Issue 5 and issue 6A, heatsink easily visible above the edge-connector, three 0.6” chips visible from the edge-connector.
Determining between Issue 3, issue 3B, issue 4A, issue 4B is a bit difficult.
Same applies determining between issue 5 and issue 6A, which is also a bit difficult. Although not many issue 5 boards were apparently produced compared to issue 6A boards.

However, if we are talking a ZX Spectrum+, with a LED torch, you may be able to see enough of the issue number screen print on the PCB through the front edge ventilation slots.

The colour of the PCB, the capacitors and resistors, etc all varied depending on what components were available at the time of manufacturing. And the serial numbers are only very loosely related to the board issue (a higher number serial number just meaning a later issue board is more likely). But keep in mind that when machines were serviced, sometimes a different board was used in the ‘old’ case.

We are still puzzling over the colour of the stickers and the colours of the serial number printing...

Membrane colour is unlikely to be helpful, as replacements have been available for many years, and this is the component that is most likely to have been replaced.

Mark

albertusj
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Re: Identifying Board Version

Post by albertusj » Sat Jul 13, 2019 7:27 pm

Thank you
ZX80/ZX81/ZX Spectrum

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