Taito Switching power Supply Help..

DarrenA

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OK, so I recently got a Space Invaders II color cocktail and I am working on repairing it.
But I have some issues I need an assist with.

First was the power Supply, it had No +5 or -5 output. I traced all of that section and found a pile of faulty parts, (about 10) from Diodes, resistors, to the high speed switching transistor. I replaced them all and now with NO load it has a nice 5.09 volt and -5.01 output.

BUT when I install the game board, the voltage on the +5 buss drops to 3.75 or lower.
Would "failing filter caps" on the +5 output cause this type of load drop?

Also what is a good test to do for a "load test" on a switching power supply?
I remember reading something about adding a resistor from +5 to ground to simulate a load but I can't find that anylonger.
 
Filter caps can cause the issue.

You can use a resistor to load the supply but I tend to use a 6.3 or higher light bulb so I can see the changes while looking for the bad guy(s).

This is the link I think you were/are looking for.

http://forums.arcade-museum.com/showthread.php?t=230524&highlight=switcher+supply+load


OK, so I recently got a Space Invaders II color cocktail and I am working on repairing it.
But I have some issues I need an assist with.

First was the power Supply, it had No +5 or -5 output. I traced all of that section and found a pile of faulty parts, (about 10) from Diodes, resistors, to the high speed switching transistor. I replaced them all and now with NO load it has a nice 5.09 volt and -5.01 output.

BUT when I install the game board, the voltage on the +5 buss drops to 3.75 or lower.
Would "failing filter caps" on the +5 output cause this type of load drop?

Also what is a good test to do for a "load test" on a switching power supply?
I remember reading something about adding a resistor from +5 to ground to simulate a load but I can't find that anylonger.
 
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Thats close, the link I had found gave me specific resistor combos to use to get a large enough draw to see if it indeed had voltage drop.

And that is my problem to a T, when I say use a small light bulb, it does put out 5.09 volts, and I can adjust it up and down with the Pot, but when I connect the real arcade board, it pukes out at 3.75 volts or so, and I can not adjust it to anywhere near 5.0 volts.

I did order a whole batch of new caps, just going to shotgun it and see if it helps.
I did pull a few caps off the PS, and I did test with a ESR meter, the readings were somewhat confusing. When I test the cap, right away after pressing the button, it reads really low, 250 or so, but the longer I hold the button down, the higher the readings, till it finally gets to say 2500 or so. this takes 3 to 5 seconds.
BTW these caps are 2200Uf 10 V
 
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