Author Topic: How do you bench test a power supply? (Read 5625 times)

rapidroy · « **on:** June 30, 2018, 03:47:09 pm »

hi all
So my Bally 5000plus power supply died and I have it on the bench but I donâ€™t know how to turn it on outside the game? Most computer ps you jump a wire and it turns on Iâ€™m thinking this is the same.

Amechanic · « **Reply #1 on:** June 30, 2018, 05:03:23 pm »

First thing I would do is open up the PS and look for any bulging or leaking caps..

rapidroy · « **Reply #2 on:** June 30, 2018, 06:07:12 pm »

I did and used my ESR tester. I guess I can put 110v at the bottom input but there got to be a way to jumper it.

rapidroy · « **Reply #3 on:** July 01, 2018, 08:30:40 am »

went through with the ESR again and found a bad cap

but cant find one in my junk box so i have to wait till monday to get to the part store. I'll just power it up at the 110v input and bypass all the other stuff on the bally ps to test.
330mf 25v

rapidroy · « **Reply #4 on:** July 02, 2018, 10:20:09 pm »

replaced the cap and got the 5v back, machine is back working. now the top and belly lights are out i think its the ballast's . more testing Tuesday.

Badbaud · « **Reply #5 on:** July 02, 2018, 10:29:30 pm »

80% of the time that cap causes a problem. There is some negative voltage being applied during some of the charge cycle and it makes the capacitor fail prematurely.Another weird problem is the 150K 1/2W resistors across the two main caps, if they change value the PS won't power up.If the power supply chirps briefly before coming to life it means it is time to replace the 6 large capacitors inside the heatsink frameotherwise the main MOSFET blows along with the .33 Ohm resistor near the fuse.

rapidroy · « **Reply #6 on:** July 03, 2018, 06:48:46 am »

its funny i heard the chirp and thought what the heck is that. so out comes the ps again and new caps going in.

Badbaud · « **Reply #7 on:** July 03, 2018, 07:24:23 am »

To the original question:I made a load bank of high wattage resistors, one bank for each of the voltages, to load the power supply at each outputs voltage maximum current rating.A power switch is added for each voltage so I can load one voltage at a time or all switches on to load all voltages at once.The resistors do get hot but it allows me to troubleshoot the circuitry a section at a time using my scope and volt meter.When I think the power supply is fixed I let it run under full load for an hour to ensure it is really fixed.

rapidroy · « **Reply #8 on:** July 03, 2018, 08:52:23 am »

Do you know the size of the 6 caps so i can get them first then just install them.

Badbaud · « **Reply #9 on:** July 03, 2018, 02:03:07 pm »

C23 & C24 = 4700uF 10VC30 & C31 = 2200uF 10VC35 = 1000uF 35VC36 = 330uF 35V
I usually replace the 10V caps with 35V caps, easier to find at a parts store.

Amechanic · « **Reply #10 on:** July 03, 2018, 03:28:29 pm »

C23 & C24 = 4700uF 10V, C30 & C31 = 2200uF 10V, C35 = 1000uF 35V, C36 = 330uF 35V
I usually replace the 10V caps with 35V caps, easier to find at a parts store.

Alan. I edited your post. It was hard to read. I added a couple commas.

Badbaud · « **Reply #11 on:** July 03, 2018, 05:08:53 pm »

(line 1) typed them line by line with a KB return after each line.(line 2) Seen this happen before with NLG.(line 3) Is their text editor broke?

rapidroy · « **Reply #12 on:** July 04, 2018, 03:29:02 pm »

still need to recap but here it is

Amechanic · « **Reply #13 on:** July 04, 2018, 03:48:23 pm »

Nice looking game 👍 perfect for todayâ€™s 4th of July.. 💥

Badbaud · « **Reply #14 on:** July 04, 2018, 04:22:30 pm »

Quote from: Badbaud on July 03, 2018, 05:08:53 pm

(line 1) typed them line by line with a KB return after each line.(line 2) Seen this happen before with NLG.(line 3) Is their text editor broke?

See it happened again??! All bunched into one line.

Badbaud · « **Reply #15 on:** July 04, 2018, 04:24:14 pm »

Re-cap sooner then later.
I see you got your lamps working.

rapidroy · « **Reply #16 on:** July 04, 2018, 10:13:56 pm »

going to pick up the caps tomorrowthe top lamp i traced down to a bad crimp on one of the pins on the molex connector. the belly lamp had a bad lamp and starter.

rapidroy · « **Reply #17 on:** July 06, 2018, 04:15:06 pm »

I just pulled the ps and the 1000mfd is a 65v maybe someone replaced it?
Keypad has arrived thanks Badbaud

Badbaud · « **Reply #18 on:** July 06, 2018, 04:35:47 pm »

I did that once, the caps looked good, they were replacements from originals, thought they would pass so powered up the supply for a 1 hour load test under full load.A couple chirps could be heard before full voltage.
20 minutes into the test and POW! blew the MOSFET, some resistors and some transistors.
Ya, the caps looked new, they had been replaced some time in the past, but when? how long ago?Those brief chirps tell the story, the caps were old.
The power supply should never chirp, not even once, upon power up.

rapidroy · « **Reply #19 on:** July 06, 2018, 04:45:39 pm »

I ordered all caps so all caps are getting replaced (should be here next week from Mouser)and even without a load the ps chirped on the bench. Iâ€™m getting a good 5.16 v but only 22v, 11v we will see after the recap.

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Author Topic: How do you bench test a power supply? (Read 5625 times)