Hello everyone, I’ve dipped my toe back into the world of the Spectrum and have bought a 48k+ on eBay.
I’ve gone to switch it on for the first time and as soon as the Sinclair copyright info appears at the bottom of the screen the letter K starts racing across the screen. I thought the key might be stuck so I pulled it out and the letter kept on scrolling. It will only stop if you press and hold down another key.
The seller has performed the following mods: recapped it, fitted a new membrane, replaced TR1 and TR2, composite mod and a heat sink fitted to the ULA. It’s an issue 3 motherboard.
Any thoughts on what could be causing it?
Thanks
Scrolling K on 48k+ start up
Re: Scrolling K on 48k+ start up
Welcome [mention]alanpwhelan[/mention]
It sounds like the keyboard membrane may need replacing.
It sounds like the keyboard membrane may need replacing.
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- Drutt
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Re: Scrolling K on 48k+ start up
Thanks for that.
I’ve seen various sellers on eBay selling membranes, is there a particular seller, eBay or elsewhere, that anyone would recommend?
I’ve seen various sellers on eBay selling membranes, is there a particular seller, eBay or elsewhere, that anyone would recommend?
- Ast A. Moore
- Rick Dangerous
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Re: Scrolling K on 48k+ start up
Some modern membranes are of poor quality. Looks like the membrane was assembled before the conductive paint fully cured. You should be able to fix that by gently massaging that area.
On the other hand, if by “pulling out” you meant you disconnected the membrane from the logic board, this means that one of the lines got stuck. Since you can’t get the letter K to appear by pressing the “K” key, I assume you mean the K mode cursor. Then it’s likely that it’s the SPACE key that is stuck.
The SPACE key are pin 1 on KB1 and pin 8 on KB2. I’d start by carefully following the trace coming from pin 1 on KB1 and making sure there are no shorts (e.g. solder splatter, etc.) or breaks. Also check R69. Then do the same by following the trace from pin 8 on KB2. Check D8. Finally, reseat the ULA.
On the other hand, if by “pulling out” you meant you disconnected the membrane from the logic board, this means that one of the lines got stuck. Since you can’t get the letter K to appear by pressing the “K” key, I assume you mean the K mode cursor. Then it’s likely that it’s the SPACE key that is stuck.
The SPACE key are pin 1 on KB1 and pin 8 on KB2. I’d start by carefully following the trace coming from pin 1 on KB1 and making sure there are no shorts (e.g. solder splatter, etc.) or breaks. Also check R69. Then do the same by following the trace from pin 8 on KB2. Check D8. Finally, reseat the ULA.
Every man should plant a tree, build a house, and write a ZX Spectrum game.
Author of A Yankee in Iraq, a 50 fps shoot-’em-up—the first game to utilize the floating bus on the +2A/+3,
and zasm Z80 Assembler syntax highlighter.
Author of A Yankee in Iraq, a 50 fps shoot-’em-up—the first game to utilize the floating bus on the +2A/+3,
and zasm Z80 Assembler syntax highlighter.
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- Drutt
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Re: Scrolling K on 48k+ start up
Yes I meant the K mode cursor. Thanks for your replies
- 1024MAK
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Re: Scrolling K on 48k+ start up
Yeah, it could just be dirt or a mechanical problem with the keyboard causing the membrane 'bubble' to be pressed for the contacts for the [space] key.
As suggested above, very carefully disconnect one of the membrane tails and then power up and see if the problem is still present.
New membranes are available from Sell My Retro
Mark
As suggested above, very carefully disconnect one of the membrane tails and then power up and see if the problem is still present.
New membranes are available from Sell My Retro
Mark
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Step up to red alert. Sir, are you absolutely sure? It does mean changing the bulb
Looking forward to summer being good this year.
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- Drutt
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Re: Scrolling K on 48k+ start up
Thanks Mark.