Spectrum+ 48k repair

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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Ast A. Moore
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Re: Spectrum+ 48k repair

Post by Ast A. Moore » Sun Sep 22, 2019 1:50 pm

Slauri wrote:
Sun Sep 22, 2019 1:43 pm
In my opinion, it looks like lower ram fault. But i'm still a beginner in these things.
No. In that case, the border would have still turned white (unless one of the lower RAM ICs was hogging the data/address lines).
Slauri wrote:
Sun Sep 22, 2019 1:44 pm
Issue 2
Wait, so you have an Issue 2 board in a Spectrum+ case?
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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.

Slauri
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Re: Spectrum+ 48k repair

Post by Slauri » Sun Sep 22, 2019 2:07 pm

Yes
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Re: Spectrum+ 48k repair

Post by Slauri » Sun Sep 22, 2019 4:31 pm

How do i check the voltages?
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Re: Spectrum+ 48k repair

Post by Slauri » Sun Sep 22, 2019 4:42 pm

It's actually my uncle's old speccy. He bought it used. That would explain the mods.
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Ast A. Moore
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Re: Spectrum+ 48k repair

Post by Ast A. Moore » Sun Sep 22, 2019 6:01 pm

Slauri wrote:
Sun Sep 22, 2019 4:31 pm
How do i check the voltages?
Set the multimeter in the DC voltage mode, select the 20V range, and touch the black (common) probe to the pin marked as GND in each picture and the red probe to the other pins as indicated. The indicated voltage values are nominal; your actual measurements might deviate slightly from them.

Lower RAM:

Image

CPU:

Image

ROM:

Image
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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.

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Re: Spectrum+ 48k repair

Post by 1024MAK » Sun Sep 22, 2019 9:04 pm

Please note that it is very important that you don’t accidentally short out any of the pins on the chips. So be careful with your meter probes.

Can you post a photo of the power supply that you are using.

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Re: Spectrum+ 48k repair

Post by Slauri » Mon Sep 23, 2019 4:54 am

Image
Image
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1024MAK
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Re: Spectrum+ 48k repair

Post by 1024MAK » Mon Sep 23, 2019 6:34 am

Going on the rating plate/label, that power supply looks fine.

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Re: Spectrum+ 48k repair

Post by Guesser » Mon Sep 23, 2019 11:58 am

Ast A. Moore wrote:
Sun Sep 22, 2019 1:50 pm
Wait, so you have an Issue 2 board in a Spectrum+ case?
I have an issue 2 Spectrum+, it's an Upgrade case.
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Ast A. Moore
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Re: Spectrum+ 48k repair

Post by Ast A. Moore » Mon Sep 23, 2019 12:29 pm

Guesser wrote:
Mon Sep 23, 2019 11:58 am
Ast A. Moore wrote:
Sun Sep 22, 2019 1:50 pm
Wait, so you have an Issue 2 board in a Spectrum+ case?
I have an issue 2 Spectrum+, it's an Upgrade case.
Sure, I know they existed. It’s just they don’t pop up all that often; so, whenever I see someone mention a Spectrum+, I assume it’s an Issue 4A or later.
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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.

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