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 Game Gear recapped. Still no picture/audio

Reply to topic
Author Message
  • Joined: 15 Nov 2020
  • Posts: 6
Reply with quote
Sega Game Gear recapped. Still no picture/audio
Post Posted: Sun Nov 15, 2020 6:01 pm
Hi all! So I'm trying to get a Sega Game Gear working that a friend got from a garage sale. It turns on, but the screen comes up black. The Brightness knob doesn't seem to have any affect.

Also, no sound from the speaker. But, I can hear sound if I plug in headphones. Volume knob works and everything. I know for a fact that the game plays. I can hear sound effects when I press buttons, but nothing on the screen.

I bought a capacitor kit off eBay and replaced all the capacitors on all three boards, but same results. Anyone know if there's anything else I can try? Thanks so much in advance!

  View user's profile Send private message
  • Joined: 23 Dec 2011
  • Posts: 20
Reply with quote
Post Posted: Fri Nov 20, 2020 3:26 pm
You can try using some IPA on the brightness knob. Just put some drops on the back and turn a few times. Also, if you have a multimeter, check resistance between pins (only the top 3 are used). It should read 20kOhm when the knob is turned all the way up or down.

About the sound not coming from the speaker, I would reflow the speaker. You can check for continuity between the solder pads and the ends of the connector.
  View user's profile Send private message
  • Joined: 15 Nov 2020
  • Posts: 6
Reply with quote
Post Posted: Sat Nov 21, 2020 12:24 am
Grieverheart wrote
You can try using some IPA on the brightness knob. Just put some drops on the back and turn a few times. Also, if you have a multimeter, check resistance between pins (only the top 3 are used). It should read 20kOhm when the knob is turned all the way up or down.

About the sound not coming from the speaker, I would reflow the speaker. You can check for continuity between the solder pads and the ends of the connector.


Thanks for the detailed reply!

So, I tried cleaning the brightness knob. I checked it with a multimeter, and I am always getting around 20k ohms between the first and third pins. When I move the knob, I get variable resistance between pins 1 and 2, and 2 and 3, which ranges from 0 to 20k ohms. I'm guessing this is correct?

The knob still doesn't seem to have any effect on the screen at all. No change in brightness. Wondering if there's a more serious problem with the screen.

As for the speaker, I don't think it needs to be reflowed. I get continuity between the solder pads and the ends of the connector. Although, I'm also getting continuity when I ohm straight through the speaker??? O.o I'm guessing that's not right. It probably means the speaker is shorted out, right? It needs to be replaced?

Thanks again for the help!

- UPDATE - I think I may have really messed something up now. The screen won't turn on at all, not even black like it was before, lol. All I did was take it apart to double check the resistance values on the brightness knob

I'm wondering if this thing is just shot. :P
  View user's profile Send private message
  • Joined: 23 Dec 2011
  • Posts: 20
Reply with quote
Post Posted: Sat Nov 21, 2020 10:12 am
Quote
So, I tried cleaning the brightness knob. I checked it with a multimeter, and I am always getting around 20k ohms between the first and third pins. When I move the knob, I get variable resistance between pins 1 and 2, and 2 and 3, which ranges from 0 to 20k ohms. I'm guessing this is correct?


Yeah, that sounds totally fine.

Quote
The knob still doesn't seem to have any effect on the screen at all. No change in brightness. Wondering if there's a more serious problem with the screen.


Well, if there's nothing displayed on the screen I also don't expect the brightness wheel to have any effect. Note that the brightness wheel does not change the brightness of the backlight, but how much light the LCD lets through. When the screen is completely off, it cannot become less of. Unless I'm not understanding something.

You can also try and see if anything happens when you fiddle with the ribbon cable, and don't be very gentles. Also try pushing on metallic rectangles on the LCD. Finally, you can check for continuity of the LCD pins, especially on the right ribbon cable where the supply voltage comes in.
  View user's profile Send private message
  • Joined: 23 Dec 2011
  • Posts: 20
Reply with quote
Post Posted: Sat Nov 21, 2020 11:52 am
Quote
I'm guessing that's not right. It probably means the speaker is shorted out, right? It needs to be replaced?


Forgot to add that the speaker is not necessarily bad. You could check by connecting the leads to a 9V battery. The speaker should pop when you touch the leads with the battery.
  View user's profile Send private message
  • Joined: 15 Nov 2020
  • Posts: 6
Reply with quote
Post Posted: Sun Nov 22, 2020 5:50 am
Thanks very much for the suggestions!

So I messed around with the screen, and I'm actually learning a lot about LCDs through this. I didn't realize that LCD screens don't emit their own light, and instead rely on a backlight. So yes, your description of the brightness knob makes sense. :)

Anyway, it turns out that it was the backlight that stopped working. But when I was moving around the board, it randomly came on. It stayed that way for a few minutes. But then as I was messing with the screen, it flickered and then shut off again. Looks like it might have a poor connection somewhere. Any idea where I can look?

As for the screen itself, it seems dead to the world. I messed with the ribbon cable, pressed down on the contacts. I also pressed on the metal rectangles. Nothing :p

Continuity seems good on the side ribbon cable between the LCD pins and the main board pins (I'm guessing that's what you meant). I also checked for voltage and am getting around 10 Volts on a few of the LCD pins. Does this seem right?

I'm wondering if the LCD is just bad. Is there a way I can confirm this?

As for the speaker, I did hear a pop when I connected the 9V battery. So, I guess the speaker is good. Anything else I can check for sound?

I very much appreciate all the help! Am having fun and learning a lot through this. :3

  View user's profile Send private message
  • Joined: 23 Dec 2011
  • Posts: 20
Reply with quote
Post Posted: Sun Nov 22, 2020 9:25 am
There's not much left I can suggest, unfortunately.

For the sound, check for continuity between the speaker connector pins and other components you see in the attached diagram. It's weird that the jack works and the speaker doesn't.

Similarly for the backlight, check the schematic. I would first check the fuses. It's also possible you have a broken joint somewhere that sometimes makes contact and sometimes doesn't. The fact that the LED turns on and you get sound suggests that it's on the 5V rail, but probably somewhere on the schematic I attached. You can also try pressing on the circuit board in different places and see if you can locate the problem in this way.
Screenshot 2020-11-22 at 10.17.50.png (255.37 KB)
Sound board schematic
Screenshot 2020-11-22 at 10.17.50.png
Screenshot 2020-11-22 at 10.19.03.png (145.67 KB)
Backlight schematic
Screenshot 2020-11-22 at 10.19.03.png

  View user's profile Send private message
  • Joined: 15 Nov 2020
  • Posts: 6
Reply with quote
Post Posted: Sun Nov 22, 2020 10:10 pm
Grieverheart wrote
There's not much left I can suggest, unfortunately.

For the sound, check for continuity between the speaker connector pins and other components you see in the attached diagram. It's weird that the jack works and the speaker doesn't.

Similarly for the backlight, check the schematic. I would first check the fuses. It's also possible you have a broken joint somewhere that sometimes makes contact and sometimes doesn't. The fact that the LED turns on and you get sound suggests that it's on the 5V rail, but probably somewhere on the schematic I attached. You can also try pressing on the circuit board in different places and see if you can locate the problem in this way.


That's no problem. I understand. This is getting pretty intense. Thanks for the continued input and for the schematics.

So I haven't gotten a chance to troubleshoot the backlight yet. I will update when I do.

As for the sound, I ohmed between the speaker connector pins and various other components. Everything seems to be correct. I'm getting continuity where expected.

Just for good measure, I reflowed the solder on the speaker pins. Same result. No sound on the speaker, only on the headphone jack. I agree, it is weird that it's only working on the jack. Although I did check for voltage on the speaker connector pins, and didn't read anything with the power on.

I'm wondering if there's just some issue with the sound board that I'm not seeing. Might try replacing it and the speaker for good measure.

I'll get back to you on the screen. Thanks again!
  View user's profile Send private message
  • Joined: 11 Aug 2007
  • Posts: 87
  • Location: Coimbra, Portugal
Reply with quote
Post Posted: Mon Nov 23, 2020 1:36 am
Quote
So I messed around with the screen, and I'm actually learning a lot about LCDs through this. I didn't realize that LCD screens don't emit their own light, and instead rely on a backlight. So yes, your description of the brightness knob makes sense. :)


The LCD's light comes from the (drums rolling) backlight. It's brightness is *not* controlled by the side potentiometer. The side potentiometer controls the LCD's contrast circuit as a sort of bias on its signals (but I don't know much about those details). The backlight is feed directly from the internal high voltage transformer which outputs an AC current with a constant RMS voltage (not sure how high but not pleasant to touch, probably on the order of hundreds of volts).

From what I understood you get sound from headphones but not from the loudspeaker?
  View user's profile Send private message Visit poster's website
  • Joined: 15 Nov 2020
  • Posts: 6
Reply with quote
Post Posted: Mon Nov 23, 2020 7:32 am
Yeperr!! I actually figured that out about the LCD through working on this thing, lol. Kind of a cool concept.

Anyway, I troubleshoot the backlight according to the schematic, and again I'm getting continuity where it's expected. I tried pressing on various components, but it wouldn't come on

I did get it to flicker on a couple of times when I sort of banged on one side of the screen, which led me to believe that maybe it's the bulb. I tried reflowing the solder on either side, still no dice.

To answer your question, yes. Sound out of the headphone jack, but not the speaker.

I think I'm on the verge of giving up, unless anybody else has any suggestions. If not, it's been fun, and an education if nothing else :3
  View user's profile Send private message
  • Joined: 11 Aug 2007
  • Posts: 87
  • Location: Coimbra, Portugal
Reply with quote
Post Posted: Mon Nov 23, 2020 9:28 pm
That's the way to do it :D Glad you're having fun!

You seem to have multiple problems with that game gear.

If you have issues with the loudspeaker check for continuity issues in the cable/connectors, the switched stereo jack (which turns of the loudspeaker connection when headphones are plugged in) or if the loudspeaker itself is blown. I think it is an 8 ohm speaker with 0.25W power rating. Do not use a 9V battery as you may burn its coil ( using P=V^2/R -> (9^2)/8 = 10.125W >> 0.25W) ). Test the speaker with an ohmmeter/multimeter.

Check the backlight's schematic (above in Grieverheart's post). To make sure that is the issue use an external lamp/led to illuminate the back of the LCD (the white difusor) while the system is running a game. If you have image/animation good. Then onto the backlight.
  View user's profile Send private message Visit poster's website
  • Joined: 15 Nov 2020
  • Posts: 6
Reply with quote
Post Posted: Tue Nov 24, 2020 5:51 pm
C3R14L.K1L4 wrote
That's the way to do it :D Glad you're having fun!

You seem to have multiple problems with that game gear.

If you have issues with the loudspeaker check for continuity issues in the cable/connectors, the switched stereo jack (which turns of the loudspeaker connection when headphones are plugged in) or if the loudspeaker itself is blown. I think it is an 8 ohm speaker with 0.25W power rating. Do not use a 9V battery as you may burn its coil ( using P=V^2/R -> (9^2)/8 = 10.125W >> 0.25W) ). Test the speaker with an ohmmeter/multimeter.

Check the backlight's schematic (above in Grieverheart's post). To make sure that is the issue use an external lamp/led to illuminate the back of the LCD (the white difusor) while the system is running a game. If you have image/animation good. Then onto the backlight.


Thank you!

Yeah, I already checked continuity in the circuit, including the cable/connectors and the switched stereo jack. All good. As for the speaker, I don't actually have an ohmmeter that can detect resistance that low. But I did hear popping when I checked it before with a 9V battery. Although, sounds like maybe I shouldn't have. :P Good point with the power equation. That was a nice refresher.

As for the display, I know for a fact that both the screen and the backlight aren't working. Initially the backlight lit up, but the screen stayed black with no animations. Also, the brightness knob had no effect.

Later, the backlight just randomly quit working. I troubleshoot it using the schematic, but couldn't find a problem. Thinking maybe the bulb is blown.

This unit is pretty messed up. :p Think I'm just gonna give up and give it to a friend. But this was fun! Sometime down the road, I think I'd like to try again with another game gear.

Thank you all again for all the help and input!
  View user's profile Send private message
Reply to topic



Back to the top of this page

Back to SMS Power!