| Author |
Message |
- Joined: 04 Mar 2018
- Posts: 3
|
Unreadable Game Gear Screen
 Posted: Sun Mar 04, 2018 8:03 pm
|
Hello everybody and congratulations for having such a big community supporting all these great Sega systems despite their age.
Last week I received a Game Gear suffering from the dim screen issue. After a teardown, I forund four capacitors in bad state, so I decided to directly replace all of them. It is a 1 ASIC version.
After recapping the system, the sound and the screen started to work as they should. However, I discovered a new issue: the screen was "glitched". I attach photos of what I am referring to.
I have very little experience with portable systems. However, I have already repaired some old computers/consoles, and my experience tells me that this can be either a video-processor (not a PPU :D) problem or a RAM (maybe VRAM?) problem (I have had similar problems with a Commodore PC with faulty RAM).
Before touching or replacing anything, any ideas about what/where could the problem be or how to test the different IC and parts of the motherboard? Any hint about how to solve the issue?
Any help will be welcomed. Thank you.
By The Way: Please, it could be great if you could avoid answers of the type "That's a lost console. It is cheaper to buy another one". I perfectly know that that may be totally true, and a repair may be more expensive, but I really want for this Game Gear to return to life.
|
| |
 
|
- Joined: 05 Nov 2014
- Posts: 435
- Location: Auckland - NZ
|
Posted: Mon Mar 05, 2018 8:15 am
|
|
Given its happening on the bios screen at power up im going to suspect its not just dirty cart contacts. Try looking around the video memory. If there is anything left behind from the leaking caps i would give it a really good clean with some alcohol and see what happens. Also check for corrosion in that area of the board. If its effecting legs on a chip theyll have gone all green and nasty otherwise itll be discoloration in the tracking. Best to follow it through with a multi meter and check for continuity if you find anything in the tracking. It can appear ok but still actually have breaks in the tracking or vias (connections between top and bottom side of board).
|
| |
|
- Joined: 04 Mar 2018
- Posts: 3
|
Posted: Tue Mar 06, 2018 4:16 pm
Last edited by pkmpad on Tue Mar 06, 2018 8:08 pm; edited 1 time in total
|
wasup wrote Given its happening on the bios screen at power up im going to suspect its not just dirty cart contacts. Try looking around the video memory. If there is anything left behind from the leaking caps i would give it a really good clean with some alcohol and see what happens. Also check for corrosion in that area of the board. If its effecting legs on a chip theyll have gone all green and nasty otherwise itll be discoloration in the tracking. Best to follow it through with a multi meter and check for continuity if you find anything in the tracking. It can appear ok but still actually have breaks in the tracking or vias (connections between top and bottom side of board).
Thank you very much for your answer.
I have recleaned everything by using isopropyl alcohol. The board seems to be completely clean. Some of the glitched parts of the screen are repaired now. I had the hope that if I continued cleaning the board, I would finish recovering the whole image, but that turned out not no be true.
By the way, using the continuity function of my multimeter, I found that 3 of the SMD ceramic capacitors seem to be short circuited. On of them is a very tiny one from the power board (C8), and the other two are C36 and C71 from the main board. Should I replace them? If so, how can I know now their original value to buy capacitors of the same capacitance? I have not any other GG to take measures.
Thank you.
|
| |
|
- Joined: 04 Mar 2018
- Posts: 3
|
Posted: Tue Mar 06, 2018 7:25 pm
|
Update: Taking a look at the GG schenatics, I (sadly) found that C36 is responsible of the '1' button, and C71, of the fluorescent tube. C8 controls a pin on the Power Board's IC Images attached.
Should I replace them anyway?
On the C8 cap, what does the 'k' next to the 'U.' mean?
|
| |
|
- Joined: 05 Nov 2014
- Posts: 435
- Location: Auckland - NZ
|
Posted: Thu Mar 08, 2018 8:26 am
|
If there shorted then id be replacing them. Once you take them off check them again with a meter and test them out of circuit. Ceramic caps are usually fairly reliable but if theyve been exposed to the electrolite thats leaked out of the old electrolytic caps then they could definately be bad.
Another thing to have a quick check of is the cart socket. Check thats not full of dust and fluff. I had a unit that did weird things and i found a pile of crud in the cart socket. Cleared that out and gave it a good clean and it all came right. I suspect it had taken moisture on and become slightly resistive and was causing data bus issues.
|
| |
|
- Joined: 28 Sep 1999
- Posts: 1197
|
Posted: Fri Mar 09, 2018 2:03 pm
|
If the games seem to work (e.g. you can hear music, pressing START enough times seems to advance the game, etc.) and only the display is corrupt, it's definitely a VRAM issue.
I would look at the VRAM address lines since the data lines seem OK. Maybe do a continuity test with your multimeter from the VRAM address pins to whichever chip they go to in your GG and make sure they are all good. Inspect the pins at both ends of the address lines for damage, and look for lifted or bent pins too.
Do you have a flash cart of some kind for running diagnostic programs?
|
| |
|
