Category Archives: ZX Spectrum 48k

ZX Spectrum 48k update #2

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The new keyboard membrane arrived from the UK.
I replaced the membrane and it worked perfectly.

I also replaced the 7805 5v power regulator with a TSR 1-2450 switched regulator.
This one does not produce any heat, så the temperature inside the Spectrum should now be very much cooler.

I also hooked up the Interface One adapter that allows connecting a microdrive.

And on the rear of the Interface One i connected the Multiface One, that allows saving programs to microdrive or tape.
It also allows to pause a game and enter a poke that for example gives endless lives in a game. 🙂

Tested it all, and it works as designed.
Perfect, next project… 🙂

ZX Spectrum 48k update

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I got the capacitors in the mail, and replaced them all.

Apparently, the positive end of the C46 capacitor was wrongly marked on the circuit board.
I documented the capacitors on this issue two motherboard, for future use. 🙂

When tested, the image still had that yellowish tone, so it was time to adjust VR1 and VR2.

I used my oscilloscope attached to the composite wire to get the noice level as small as possible.

Much better, now it is white as it should be. 🙂

Can’t test anything else right now, because i am waiting for the new keyboard membrane from UK to arrive.

To be continued. 🙂

ZX Spectrum 48k home computer

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This is a Sinclair ZX Spectrum 48k home computer released in 1982.

I bought this one new in the mid 80’s. (This is an issue two.)
When i upgraded to a C64 i sold it to one of my cousins.
I got it back a couple of years later when my cousin was not using it anymore.
Then it has been in storage ever since.

It is booting, but with a distorted image.
It only has RF output via an RCA on the backside.
But since i want to use composite video, i will have to do a mod. 🙂

The keyboard membrane connectors were bad, so i could not try anything else but to power it up.
(I have ordered a new membrane from the UK, and i will replace it when it arrives.)

All the capacitors will be replaced as well.
(Same here, had to order some and will replace them later.)

I did the composite mod and tried it on my monitor.
Much better, but with a yellowish tone.
I will adjust the VR1/VR2 when the caps have been replaced to see if this will fix it.

To be continued. 🙂