Forums

Sega Master System / Mark III / Game Gear
SG-1000 / SC-3000 / SF-7000 / OMV
Home - Forums - Games - Scans - Maps - Cheats - Credits
Music - Videos - Development - Hacks - Translations - Homebrew

View topic - Sega Mastersystem 1: issue with signal turn it on and doesn't register signal first time

Reply to topic
Author Message
  • Joined: 23 May 2022
  • Posts: 2
Reply with quote
Sega Mastersystem 1: issue with signal turn it on and doesn't register signal first time
Post Posted: Mon May 23, 2022 1:22 pm
bios V1.3 board was the original European pal board is a 1987 "snail game"

So the issue is that it doesn't get a signal to the tv every time you hit the power button, you have to keep turning it on and off until it connects.

usually second time but sometimes takes a while.

I was wondering if this might be a problem with the capacitors charging and discharging - I do have a full set I can replace but I don't want to if I don't need to.

Other issues I could think of are the video encoder chip or the Video chip itself. I have checked all the traces and no stains or corrosion is present on the board.

it exhibits the same behavior with or without a cartridge. I don't own any cards so unable to test but I guess it would be the same.

It works fine otherwise - I can play games and all so If I can't find the answer I don't think I will mess with it.

Any advise would be welcome.
  View user's profile Send private message
  • Joined: 05 Nov 2014
  • Posts: 428
  • Location: Auckland - NZ
Reply with quote
Post Posted: Fri May 27, 2022 6:38 am
I would change the capacitor that forms the reset signal. If thats on the way out then it might not be holding the system in reset long enough during power up. That could give you plenty of randomness but working fine when it does like your seeing.

I dont know which one it is off hand and its a bit hard to look at on my phone but if you pull up the service manual and follow the reset pin on the z80 itll go to a cap and resistor that connect between +5 and ground. Thats the cap you want to change.
  View user's profile Send private message
  • Joined: 23 May 2022
  • Posts: 2
Reply with quote
Perfect this worked a treat.
Post Posted: Sun May 29, 2022 12:33 pm
wasup wrote
I would change the capacitor that forms the reset signal. If thats on the way out then it might not be holding the system in reset long enough during power up. That could give you plenty of randomness but working fine when it does like your seeing.

I dont know which one it is off hand and its a bit hard to look at on my phone but if you pull up the service manual and follow the reset pin on the z80 itll go to a cap and resistor that connect between +5 and ground. Thats the cap you want to change.


Yeah I did as you said and replaced the cap - works perfectly now.

Thanks man! :)
  View user's profile Send private message
Reply to topic



Back to the top of this page

Back to SMS Power!