Samsung Issue 3 oddity

For experts to discuss very technical stuff and newbies to ask why the Spectrum they bought off ebay doesn't work.
Post Reply
Lucifer-Starr
Drutt
Posts: 2
Joined: Tue Sep 03, 2019 3:11 pm

Samsung Issue 3 oddity

Post by Lucifer-Starr »

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
https://drive.google.com/open?id=1n1xop ... z6T6evIwmW
Odd diodes and additional capacitor?
https://drive.google.com/open?id=1sQCMI ... VMErKn4NYY
Another angle
https://drive.google.com/open?id=1tkgXV ... rGkqejKMrx
Additional resistor?
https://drive.google.com/open?id=1jUBzY ... GO2TE9gsME
Another angle
https://drive.google.com/open?id=1MnhiI ... EkJWajkKh1
These points are where the reset was connected - normal on an issue 3 or weird choice?
https://drive.google.com/open?id=1vEdXG ... PiPLD8AGrg
User avatar
1024MAK
Bugaboo
Posts: 3104
Joined: Wed Nov 15, 2017 2:52 pm
Location: Sunny Somerset in the U.K. in Europe

Re: Samsung Issue 3 oddity

Post by 1024MAK »

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
:!: Standby alert :!:
“There are four lights!”
Step up to red alert. Sir, are you absolutely sure? It does mean changing the bulb :dance
Looking forward to summer later in the year.
Lucifer-Starr
Drutt
Posts: 2
Joined: Tue Sep 03, 2019 3:11 pm

Re: Samsung Issue 3 oddity

Post by Lucifer-Starr »

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