No pcb serial Numbers, so any Lists of provenance?

[VinCBR900]

Hi All,
Im new here, and have taken posession of a poorely zx81 issue one.

Mine is ULA 2C158e date code 8106, Zilog z80cpu date code 8147, Mostek 1kx8 sram date code 8038. Modulator date code is 8107. Rom is missing. The sram and ula are quiet early, but the modulator and cpu are later. This seems odd to me.

I tried a search, but is there a list somewhere of buggy rom date codes/versions, ULA versus pcb issue, and versions which had 1kx8 vs two 2114s during the great sram shortage of the early 1980s? I.e.

• Issue 1: ULA 2C158e up to date code XXYY, mostek 1k by 8 to date code, buggy rom always fitted to 1kx8 sram boards and issue 1 pcbs?
• Issue 2: ULA 2c184 up to date code AABB, 2c210e afterwards, always mostek 1kx8 sram?
• Issue 3: ULA 2c184e to date code EEFF, ULA 2C210E date code onwards

Not sure if sinclair radionics/thandar/sinclair research etc were hot on keeping these types of records...

Cheers, Vincent

[gozzo]

Never seen a 2C158E ULA, but plenty of the other 2 - the 2C184E version seems to fail more than the 2C210E version (have several '81's with duff 2C184E ULA's but never yet some across a duff 2C210E! ) As for 'buggy' ROM - there is a software test you can do to find out which it is (although not a lot of good if the ZX is not working at all ) (don't know which date codes are 'buggy' , unfortunately) SRAM - have seen some issue 1's with 2 2114's, some with 1 4118, same with issue 3's - never come across an issue 2 board yet, though!??! One of my issue 3's was fitted with a 2K Toshiba 2016 RAM chip, but with the link set for 1K - maybe sinclair used some half-duff 2K chips for cheapness??? As for the mix of date codes - quite possible - certainly is with my ZX81's! Should be possible to 'burn' an EPROM with the 81 ROM image to replace the missing ROM, but will need to make an adaptor socket (not too difficult) as the connections for the ROM and EPROM's such as the 2764 or 2564 are a bit different.

[Moggy]

Hi Guys
Welcome to the forum

Some of this was touched on in this thread....

viewtopic.php?f=7&t=451

Vincent Your 2C158E 8106 ULA is, I think, the earliest recorded here, I have two 8113's and another forum member , Angus has an 8112, 2C158E.

Does Yours have the CPU hardware workaround added as a stopgap measure until "good" ROMS went into production? (picture included in rar file), like a lot of early 81's Yours has a Zilog CPU as opposed to NEC.

As for issue 2 boards I have been collecting since day one and never seen one.

You can use 2764 EPROM with a simple bit of pin rewiring, I use David Husbands, Forth ROM on a 2764, the only problem I have come across when using a 2764 as a standard 81 ROM is one of timing conflicts when using external ROM boards fitted with 2716, 2732 EPROMS or battery backed memory boards with 6116 chips.

Gozzo You could be right about the Toshiba chip , Think Spectrum RAM and Texas instruments! Uncle Clive at His inventive best


Again welcome.
Regards Moggy

[VinCBR900]

Thanks chaps.

Im not worried about Eproms etc - easier to use an emulator. Im trying to decide if it is worth resurrecting, but the 'first' production zx81 might be worth fixing. I dont know if it works yet - another is on its way from a well know auction site.

It does not have the rom bug fix on the cpu, picture when I can get a good shot without flash reflecting off the heatsink and silver traces. If teh ULA works it might be nice to install a buggy rom and cpu bodge board if I can find one.

Ill see if there are any other responses but it doesnt look like this kind information is tabulated anywhere.

Thanks, Vincent

[Moggy]

To be honest Vince I don't think You will find what You are looking for from a point of view of lists etc.
To be blunt Uncle Clive didn't give a toss about about His computers other than make them as cheap as possible, His interest lay in electric vehicles and the tooters were a way of paying for them, so lists were the last thing on His mind.

Like a lot of one Man band inventors making it was the thing not keeping inventory.
As a musician I keep coming up against Younger guys fawning over a certain 50/60's amplifier manufacturer, talking about every change of transformer speaker etc in hushed tones, but the truth of the matter is the original owner was a cheap son of a bitch who made changes only from a point of view of lining His own pocket; so the amps that were crap in 63 are crap now but people with more money than sense will pay the Earth for them.

The point of this being is that many famous inventions were built by little more than "cottage industries" and keeping tabs on what went into these creations was the last thing on Their mind, so asking for lists is , I think , futile.

Though having said that as most 81's were built by Timex at Dundee I would say they are pro enough to have kept records so perhaps You search should start there.

Regards Moggy

[VinCBR900]

Hi Moggy,
thanks for the diatribe I think I know about the particular guitar amp you refer to with military connections. FYI, Blackstar Amps are a northamptom based company who seem to be doing very well.

However, most of these guys do whats needed to keep small companies up and running, like gates using the MITS mainframe to write their comercial Micro-soft BASIC for the Altair - a bit naughty.

I was just asking in case anyone knew of any lists already in existance. Eventually it will be be Googled and them some ex Sinclair employee may reveal that the Issue 2 was only ever internal to Sinclair etc. You never know who might be listening...

Cheers, Vincent