Pictures of my ZX81 fitted with a RECOM 5V Regulator

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1024MAK
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Re: Pictures of my ZX81 fitted with a RECOM 5V Regulator

Post by 1024MAK » Sat Oct 27, 2018 4:27 pm

Yes, the issue 3 board is very similar. The unused holes for the switch are exactly the same. The pads for the 9V DC input socket are laid out the same, but I can’t remember if the holes in the board are the same as on the issue 1 board.

I added the 100nF capacitors because they help with the reduction of noise and the stability of the regulator/ DC-DC converter.
I got mine from Rapid Electronics (who have since discontinued this make and replaced them with a different make). The type that you linked to up thread should be fine.

The idea is to have a 100nF capacitor on the 9V DC input to the regulator/ DC-DC converter as close to it as possible (this is good practice for conventional series pass 78XX regulators where the main smoothing capacitor is remote from them anyway).

The 100nF capacitor on the 5V output of the regulator/ DC-DC converter is also good practice.

Mark

Lardo Boffin
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Re: Pictures of my ZX81 fitted with a RECOM 5V Regulator

Post by Lardo Boffin » Sat Oct 27, 2018 4:44 pm

Thanks Mark. Do these just go into spares holes without making any more changes? Or do you have to divert the power away from its original route to send it through the capacitors?
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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Joined: Mon Sep 26, 2011 10:56 am
Location: Looking forward to summer in Somerset, UK...

Re: Pictures of my ZX81 fitted with a RECOM 5V Regulator

Post by 1024MAK » Sat Oct 27, 2018 7:35 pm

No diversion/changes. The one that goes in the holes provided for the switch, just go in the holes (the outer two of the three). Solder it up and it’s good ;)

On some boards, there are holes that are part of the same pads as the pins/legs of the 3.5mm jack socket used for the 9V power input. But on the underside they are often covered by solder. So you have to remove some of this solder. It’s then just a case of fitting the capacitor in the holes, and soldering up both the capacitor and the socket pins.

As I said earlier, i can’t remember if the issue 3 board has these holes. If not, you may be able to slide the capacitor legs into the same holes as the pins of the socket.

Mark

Lardo Boffin
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Re: Pictures of my ZX81 fitted with a RECOM 5V Regulator

Post by Lardo Boffin » Sat Oct 27, 2018 10:46 pm

Thanks. I have opened an issue three and it has the following:-

4DE4EFCC-7D71-4038-9D86-4EE661F78B2C.jpeg

So one of the caps should be easy but not so sure about the other.

I put a mat over the heatsink to avoid glare on my phone.
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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