Samsung Issue 3 oddity

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Lucifer-Starr
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Samsung Issue 3 oddity

Post by Lucifer-Starr » Tue Sep 03, 2019 3:00 pm

Hello, this is my first post - sorry it's straight to "Help mee!!" without saying hello.
Had a Speccy 48 from (I want to say) Christmas '83. My first games being Jetpac and Ant Attack. Moved to 128+ Christmas '86, it died in warranty and was replace with a +3 which was in use until '91.
Recently been feeling nostalgic, so, I acquired an Issue 3 made by Samsung.
It fires up and loaded a Horace Goes Skiing with no issues - need to check a 48K title when I can.
It'd had a reset switch added by a previous user - super-glued to the case by the RF out :( and routed to the vias on the underside of the board, which made removing the board a pain. I've removed this - anyone know a way to remove super-glue residue without damaging the case?
Also, on the motherboard are 2 areas which don't look normal to my limited knowledge.
Anyone tell me what's going on here? Any help would be appreciated.

Board Overview

Odd diodes and additional capacitor?

Another angle

Additional resistor?

Another angle

These points are where the reset was connected - normal on an issue 3 or weird choice?
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1024MAK
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Re: Samsung Issue 3 oddity

Post by 1024MAK » Tue Sep 03, 2019 3:27 pm

Some of the changes are as per the official Sinclair DC/DC modification (see the technical details here).

The value of resistor R68 was changed to improve compatibility with the plus keyboard. For existing boards instead of removing and replacing it, it was permissible to solder another resistor on top of the existing resistor.

There is no provision for any specific PCB connections for a reset switch, so any suitable connection to the Z80 reset input line and 0V/GND can be used.

Mark
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Lucifer-Starr
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Re: Samsung Issue 3 oddity

Post by Lucifer-Starr » Tue Sep 03, 2019 10:34 pm

Thank you, Mark.
Next step recapping etc...
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