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Arcade Collecting => Miscellaneous Arcade Talk => Topic started by: perjmolsen on May 12, 2020, 12:16:00 pm

Title: China power supply no negative 5V - cap is missing!
Post by: perjmolsen on May 12, 2020, 12:16:00 pm

HI

I just got a new power supply for my restoration of Space Gun

The issue I have is that my sound is not working, I got a humming sound.

I have noticed that the negative 5 volt is not present, and it seems that this game uses the negative 5V for sound.

BUT when I opend the PSU I can see that the negative rail is not connected at all!!!

If I follow the trace from negative 5 rail, C20 is missing.

Can i just replace the missing cap wit a new cap the same value 1000uf 16v as used at the normal +5V rail?

Title: Re: China power supply no negative 5V - cap is missing!
Post by: Ken Layton on May 13, 2020, 01:47:31 am

The -5 volts rail in many brands of switching regulator power supplies typically have a single filter capacitor. Use between a 470 uf to 1000 uf @ 16 volt capacitor. It looks like simply installing the missing capacitor should restore your -5 volts. Be sure to observe the correct polarity.

Title: Re: China power supply no negative 5V - cap is missing!
Post by: perjmolsen on May 13, 2020, 03:14:43 am

Hi Ken

I have now tried to put in a 1000uf 16v cap at C20.
But no negative 5V, still 0V  :'(

Title: Re: China power supply no negative 5V - cap is missing!
Post by: perjmolsen on May 13, 2020, 03:22:55 am

Hi

Also noticed that C16 is missing...
It looks that there at some point has been a cap...

Can it be the cause to a missing negative 5V?