Hello guys,
I'm in the process of restoring, or bring back to live a GX4000, when I bought her, she has power (green light) but nothing on the screen. And the controllers with the wire's completely cut.
I was aware of the double input voltage, so I never put a power supply on the 5v in (but I can assure that someone did it before).
First time I plugged in a 9v 1A PS in the 11v in, green light appears, but some smell of burn appears in a few seconds, so I powered down immediately, and began reading in depth the forum to find the issue.
Reading about burned smell, I saw that the if the RAM was bad, it heats a lot, so I put my finger on them and it was hot as hell! So I decided to replace it.
But nothing happens, no video, no audio.
I began doing measures in the Power Board, and I find that the Voltage regulator IC181 7805 had 9v in both pins (in and out). I replace it, but same happens, and find a video in Youtube about change the Diode D183. I replace it, and now the IC181 output pins is 5V!
So, I put a multigame cartdrige (like C4CPC ) that I bought power on, but no video at all. So reading the forum I find several references to no video, but audio in the MiniJack. So I connected headphones in the jack and EUREKA! There is sound!!! I connected a repaired controller and can hear changes in the menus or in the game, so the GX4000 process is working!!
Now let's go to my problem now, I have no video on RF or on SCART. On RF sometimes I see snowed images of the games if I move the RF antenna cable. So I have a problem on the video part.
My first test was to measure the other voltage regulator IC17 that I understand that powers the video section, and the measures are weird. I suppose to have 9v in and 5v out, but I get 5v in, 3v out. I did not replace the IC17 because if it was a problem with it, I'll see 9v in, so maybe the problem is somewhere else.
Can you help me find we're the problem is? What test can I do?
I only have a multimeter to do the readings, I do not have an oscilloscope or advance tools.
Thank you in advance!!
Try check IC15 pin 15,16,17 RGB after DAC.
Hello MrArti0,
I check IC15, these values are not fixed:
15 --> 0.05v - 0.10v
16 --> 0.35v - 0.40v
17 --> 0.10v - 0.15v
Thanks for the help.
Quote from: josepprada on 09:30, 28 April 24I check IC15, these values are not fixed:
choose the game with the whitest scene and the blackest scene and check again how high and low the voltages on these pins go.
Ok, I'll try during this week and post it back the results.
Thanks!
Check whether transistors Q3,4,5 between the base and the emitter have approximately 0.7 V
Connect nsync to the sound line. You should hear a 50hz buzz in your headphones. Try connecting the LUM signal straight to the TV video input.
Hello MrArti0,
First, I cannot test the whitest game and blackest because I do not know what games I'm playing only by sound, so it's a little difficult test.
Although, today I manage to get audio from RF , and a snowy screen. I can only identify Robocop 2.
About the second answer: Q3, Q4 and Q5 with a game on, give me a measure of -3.70v -2.70v -3.70 , so it seems weird .
I did not understand the last sentence, sorry I'm not used to work on electronic, I'm kind of a noob.
"Connect nsync to the sound line. You should hear a 50hz buzz in your headphones. Try connecting the LUM signal straight to the TV video input. "
Thanks for the help!
Hello MrArti0,
Finally it's working!! I orderder a 78L05 voltage regultator, and change it today, and voila! Works perfectly!
Now I have to rewire the controllers because some buttons do not work propery, but the main issue is solve.
Thank you for your help!
Here is a Screenshoot of she working ;)
https://imgur.com/a/Eww5bwl
Woohoo. And welcome to the GX owners club.
Thank you Andy!
I'm proud to join the club!