The phantom key press (menace)

Lardo Boffin
Posts: 2160
Joined: Sat Nov 26, 2016 2:42 am

The phantom key press (menace)

Post by Lardo Boffin »

Hi all

I recently bought an issue two Spectrum in order to refurb so I had one I had done myself. It's all working fine on its own - loads games fine and the iPod turbo loader is an absolute revelation! Manic miner loading in 23 seconds!

But when I connect my DIVMMC future to it weird things happen! It insists on thinking I am constantly pressing the # key, but only when it warms up. It doesn't do it for the first 30 seconds. After this point it does it every second or two. If I manage to get a game loaded it then appears to be pressing other keys on my behalf - e.g. In Manic Miner the music switches off, it pauses, unpauses and jumps etc.
I have tried a few different membranes in case it is that. No difference. I have even tried it without a membrane and it still does it.
Without the DIVMMC plugged in all is well.
The DIVMMC works fine with my issue 4B.
Unfortunately I don't have another sd card reader to test with.
I have given the edge connectors a very good clean.

Any thoughts?

Many thanks!

Lardo
ZX80
ZX81 iss 1 (bugged ROM, kludge fix, normal, rebuilt)
TS 1000 iss 3, ZXPand AY and +, ZX8-CCB, ZX-KDLX & ChromaSCART
Tatung 81 + Wespi
TS 1500 & 2000
Spectrum 16k (iss 1 s/n 862)
Spectrum 48ks plus a DIVMMC future and SPECTRA
sirmorris
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Joined: Thu May 08, 2008 5:45 pm

Re: The phantom key press (menace)

Post by sirmorris »

Lardo Boffin
Posts: 2160
Joined: Sat Nov 26, 2016 2:42 am

Re: The phantom key press (menace)

Post by Lardo Boffin »

sirmorris wrote: Wed Sep 27, 2017 10:51 am ULA.

Possible but less likely:
http://blog.tynemouthsoftware.co.uk/201 ... gnals.html
Thanks but I was hoping no one would say ULA... :cry:

The DIVMMC works ok apart from the random keypresses - I assume from the article that it would not work at all if the M1 line was dud?
ZX80
ZX81 iss 1 (bugged ROM, kludge fix, normal, rebuilt)
TS 1000 iss 3, ZXPand AY and +, ZX8-CCB, ZX-KDLX & ChromaSCART
Tatung 81 + Wespi
TS 1500 & 2000
Spectrum 16k (iss 1 s/n 862)
Spectrum 48ks plus a DIVMMC future and SPECTRA
sirmorris
Posts: 2811
Joined: Thu May 08, 2008 5:45 pm

Re: The phantom key press (menace)

Post by sirmorris »

That's my experience. No M1 = No work. I only mentioned the M1 line as it's my typical go-to.

As the problem gets worse with heat have you tried a freezer spray?
Lardo Boffin
Posts: 2160
Joined: Sat Nov 26, 2016 2:42 am

Re: The phantom key press (menace)

Post by Lardo Boffin »

sirmorris wrote: Wed Sep 27, 2017 12:12 pm That's my experience. No M1 = No work. I only mentioned the M1 line as it's my typical go-to.

As the problem gets worse with heat have you tried a freezer spray?
I don't have any freezer spray! :oops:

I will try a strong fan though - it may be sufficient to make a difference (it did on my sparkly pixel zeddy a while back).
ZX80
ZX81 iss 1 (bugged ROM, kludge fix, normal, rebuilt)
TS 1000 iss 3, ZXPand AY and +, ZX8-CCB, ZX-KDLX & ChromaSCART
Tatung 81 + Wespi
TS 1500 & 2000
Spectrum 16k (iss 1 s/n 862)
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: The phantom key press (menace)

Post by 1024MAK »

Do you have an air duster can?
If yes, hold it upside down and carefully spray the air (which will come out as a mixture of air and cold fluid) on the centre of the chip. Watch that you don't get any in your eyes or on your skin though.

Mark
ZX81 Variations
ZX81 Chip Pin-outs
ZX81 Video Transistor Buffer Amp

:!: Standby alert :!:
There are four lights!
Step up to red alert. Sir, are you absolutely sure? It does mean changing the bulb :!:
Looking forward to summer later in the year.
User avatar
1024MAK
Posts: 5102
Joined: Mon Sep 26, 2011 10:56 am
Location: Looking forward to summer in Somerset, UK...

Re: The phantom key press (menace)

Post by 1024MAK »

What board version is this Spectrum?

There is a design issue with the early boards that used the early ULA chips, in that the I/O port decoding does not work properly. The ULA then thinks any I/O operation is aimed at it...

Does the CPU have a transistor sat on top of it, or connected by a wire to one of the pins?
Or any extra resistors and diodes on top of the CPU, or nearby?

Mark
ZX81 Variations
ZX81 Chip Pin-outs
ZX81 Video Transistor Buffer Amp

:!: Standby alert :!:
There are four lights!
Step up to red alert. Sir, are you absolutely sure? It does mean changing the bulb :!:
Looking forward to summer later in the year.
Lardo Boffin
Posts: 2160
Joined: Sat Nov 26, 2016 2:42 am

Re: The phantom key press (menace)

Post by Lardo Boffin »

It's an issue two with an OKI RAM upgrade to 48K:-

IMG_7001.JPG
(2.34 MiB) Downloaded 391 times
I have asked Alex at Mutant Caterpillar Games if she will try to see if she gets the same with any issue twos her end.

My air duster can is empty! Argh. Time to order some more.
ZX80
ZX81 iss 1 (bugged ROM, kludge fix, normal, rebuilt)
TS 1000 iss 3, ZXPand AY and +, ZX8-CCB, ZX-KDLX & ChromaSCART
Tatung 81 + Wespi
TS 1500 & 2000
Spectrum 16k (iss 1 s/n 862)
Spectrum 48ks plus a DIVMMC future and SPECTRA
Lardo Boffin
Posts: 2160
Joined: Sat Nov 26, 2016 2:42 am

Re: The phantom key press (menace)

Post by Lardo Boffin »

MCG have kindly tried an issue two with an OKI RAM upgrade and it does not have the same issue. Hmmm.
ZX80
ZX81 iss 1 (bugged ROM, kludge fix, normal, rebuilt)
TS 1000 iss 3, ZXPand AY and +, ZX8-CCB, ZX-KDLX & ChromaSCART
Tatung 81 + Wespi
TS 1500 & 2000
Spectrum 16k (iss 1 s/n 862)
Spectrum 48ks plus a DIVMMC future and SPECTRA
sirmorris
Posts: 2811
Joined: Thu May 08, 2008 5:45 pm

Re: The phantom key press (menace)

Post by sirmorris »

<cough> transistor on top of the processor <cough>
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