zx spectrum +2A symbol lock always on

For experts to discuss very technical stuff and newbies to ask why the Spectrum they bought off ebay doesn't work.
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landex
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zx spectrum +2A symbol lock always on

Post by landex » Sat Jan 19, 2019 6:17 am

Hi
I have zx spectrum +2A, for years, last time I play with, it was every thing fine.
Today I tested it, and the symbol lock is always on.
What could be the issue?

Regards
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Ast A. Moore
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Re: zx spectrum +2A symbol lock always on

Post by Ast A. Moore » Sat Jan 19, 2019 8:37 am

Any number of things: the keyboard membrane, one or of the diodes D6–D22 (more specifically, D14–D22), or the gate array itself. The most likely culprit, however, is the keyboard membrane, or even some dust/dirt underneath the CAPS LOCK key. (I assume you mean that key, rather than the two SYMBOL SHIFT keys on either side of the keyboard.)

Try carefully disassembling the keyboard and cleaning it. See that clears the fault.
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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.

landex
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Re: zx spectrum +2A symbol lock always on

Post by landex » Sat Jan 19, 2019 2:59 pm

Thanks Ast, II wiil try it.
When I press the keys they return.
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Ast A. Moore
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Re: zx spectrum +2A symbol lock always on

Post by Ast A. Moore » Sat Jan 19, 2019 3:36 pm

landex wrote:
Sat Jan 19, 2019 2:59 pm
When I press the keys they return.
This doesn’t mean that the membrane underneath the mechanical key is not damaged or dirty, though. You need to disassemble the Spectrum, then further take apart the keyboard assembly, and carefully inspect the membrane for dirt or damage.
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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.

landex
Berk
Posts: 3
Joined: Sat Jan 19, 2019 6:11 am

Re: zx spectrum +2A symbol lock always on

Post by landex » Sun Jan 20, 2019 8:54 am

Thank you guys, i took the two keys from above, clean them, and now it works fine! :D
Under it its very clean, I thing it was little plastic under one key.
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