Power Supply Question for Atari?

machfelon

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I tested my PS on my 720 and the reading are high.

Getting 5.39 V at the PS

Im pretty sure this should be lower. How far should I turn the knob down on the PS to lower it by a tad?
 
Yes 5.39 is high.. but it might be warranted because...
What slackmoe is suggesting is that the important voltage is what is reaching the PCB. You will have some loss as it travels over the wires and due to
crappy connections (oxidation). Try to find a test point on the PCB or measure the 5v at the edge connector to the pcb.
 
Yes 5.39 is high.. but it might be warranted because...
What slackmoe is suggesting is that the important voltage is what is reaching the PCB. You will have some loss as it travels over the wires and due to
crappy connections (oxidation). Try to find a test point on the PCB or measure the 5v at the edge connector to the pcb.

I manually lowered the PS to 5.1 and I appear to be getting only 3.919 at the board. I tested at the bottom of the Board using the GND and 5V Lead sticking out. So should I shoot up the power to the PS since the board is getting much lower voltage?
 
Wow thats a big drop. I'd check your connectors for any that are dark/black which means they are burned and clean the edge connector of the pcb
gently with a big eraser.
 
Ok well out of curiosity I plugged in my old PS that was causing issues before. Plugged it in and game booted right up. So I then checked my voltages and this PS is running at 5.57 V but game boots and is stable. So I have a huge loss in power somewhere. But at this voltage its enough to run the game.

Im going to retry the old joystick now to see if I can get it programmed.

If I Clean all the edge connectors and this increases power to the board in theory the game should then crash correct? Because now it would be getting too much voltage to the board if its at 5.57 right?
 
If I Clean all the edge connectors and this increases power to the board in theory the game should then crash correct? Because now it would be getting too much voltage to the board if its at 5.57 right?

dont want to go over 5.35 for very long. you will damage chips and no more booty booty

if you measure the 5v along the way to the gameboard, you might be able to detect where you are getting the voltage drop

measure before and after each connector. what i did was solder on a capacitor leg onto my probe for easy access to the pin inside the connector
 
ok.. on connector p13 on video board.. what do you get on pin 8 and pin 6 while holding ground on pin 2 or 4??? cause this is the frist place the +5 enters the board set.. then check the top board

example.. pin 8 / pin 2(ground)
pin 6/ pin 4(ground) ?

by the way.. the bottom board is your VIDEO board and the top is your CPU board

one more question.. are both sense wires cut?? +and - ?? these are coming off P13 connection also

720ta.jpg
 
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I'll say it again. Save yourself future aggravation and rebuild the connectors. What I mean is, at the very least, repin all power and ground related pins.

Ed and GPE sells the connector pins and crimping tool if you need it.

http://www.greatplainselectronics.com/

Crappy connectors create resistance in the circuit. Connector pins are only rated for so many wipes (connects/disconnects). The game is what, 25yrs old? Mine seems to be working now, but I will definitely be repinning the harness.
 
I'll say it again. Save yourself future aggravation and rebuild the connectors. What I mean is, at the very least, repin all power and ground related pins.

Ed and GPE sells the connector pins and crimping tool if you need it.

http://www.greatplainselectronics.com/

Crappy connectors create resistance in the circuit. Connector pins are only rated for so many wipes (connects/disconnects). The game is what, 25yrs old? Mine seems to be working now, but I will definitely be repinning the harness.

or do bob roberts.. thats where i got all my 720 parts from.. plus with cross shipping you cant beat it!
 
Well I tested the GND anfd 5v1 on video PCB on bottom of cabinet and got 4.5V

With the switcher at 5.57

Also the connector on bottom of cabinet (white one) with like 5 or pins then couple blanks then 2 more pins shows some burnt connections though the plastic.
 
Possibly. I would dial down the switcher to 5v Clean al the edge connectors
and then measure it at the pcb and dial up if necessary. to reach 5v.
 
Well I tested the GND anfd 5v1 on video PCB on bottom of cabinet and got 4.5V

With the switcher at 5.57

Also the connector on bottom of cabinet (white one) with like 5 or pins then couple blanks then 2 more pins shows some burnt connections though the plastic.

So, if it's so bad that there's obvious burn and not just resistance due to old connectors, stop what you're doing, and rebuild the connectors before doing anything else.
 
I cleaned all connectors with eraser. Reseated everything and the lowest I can keep the game stable is 5.54 on the switcher. I still cannot get it any lower and still cant get it to read any joystick movements. Have tried everything.

Might try a whole new Harness for the joystick. Donno and it still doesnt solve the power issue.
 
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