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Bringing another ZX81 back to life

A

fter watching this video from RMC I ordered some bits from ZXRenew; a new membrane keyboard and a couple of the modulator replacements. In the past I've used the ZX-CCB and thought I'd try the ZXRenew Composite Modulator Replacement.

I knew that in my box of ZX81 parts I had one with a duff keyboard. It didn't really need that label because the connectors had obviously cracked and crumbled. 


Otherwise the case is in reasonable shape (the red ZX81 can be easily touched up). The board looks great. Most chips are in sockets and in the past I've obviously found the ULA to be good and heatsinked (heatsunk?) it.
The other side of the board is a bit fluxy, but I think this is a 'bought assembled' one.
The modulator was in good shape but pretty useless today. It's easy to remove it without damaging anything, and keep it somewhere safe. 
Here's the replacement in place. The switches determine whether the circuitry adds the 'backporch' to the video signal, which this issue 1 ZX81 needs. It has a nice yellow RCA jack to indicate Composite.
And hey presto! After a bit of twiddling, the picture looks great.  
In his video, Neil said that he was nervous about sticking the new membrane in place, and I felt the same trepidation.
Both halves of the case got a good clean and then....
It went well. Looks perfect
And works perfectly too:
What better than to test the new keyboard than a 1k type-in game? 

The game is terrible. This is my best score (the score increments in 25's)
And finally tonight, a game of 1k chess, the only computer chess game I can consistently beat. Check Mate!!


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Comments

  1. Bloke13 December 2021 at 13:53

    How did you remove all the old keyboard glue? That stuff hangs around..

    ReplyDelete
    Replies
    1. peahen13 December 2021 at 14:14

      I played a hairdryer onto it - above and below - until the glue had softened and I could peel it off. There wasn't much glue left on the case, just gave it a rub with alcohol to get rid of any residue. You can see Neil doing the same thing in the video I link to, mine went just as well as his.

      Delete
    2. Bloke14 December 2021 at 11:02

      nice. The two I've updated left a LOT of gross old glue!

      Delete

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