FIXED: Does anyone on here service PSU's?

[scaryhours]

Have a New Astro City PSU with no sound. Sent it out to a shop for a recap, but they said the caps tested fine and couldn't guarantee audio repair.

Anyone want to take a shot fixing it?

 

[trashedcabs]

Which power supply is it?

The astro city power supplies don't have amplifiers in them--they only have large high wattage pots to attenuate the speaker level. AFAIK only the 421-8741 add-on unit actually contains an amplifier to run stereo games.

Open it and verify the pot and wiring is good, that's all there really is to it. You can even completely bypass it if you want; personally I think volume attenuation between the PCB and the speakers was a stupid choice by the manufacturers.

 

[ner38073]

Have a New Astro City PSU with no sound. Sent it out to a shop for a recap, but they said the caps tested fine and couldn't guarantee audio repair.

Anyone want to take a shot fixing it?

Mine started acting weird then soon after a spark blew out and my cab was all dead. Recap it, no luck. I had to completely upgrade to Axun's JCCBOX @axunworks for arcade monitors. Rewired everything and he also custom made me the controller panel adapters and cables to his JCCBOX. Back up running better than before. Those PSU units are old and really hard to keep them running after 25+ years.

 

[scaryhours]

Which power supply is it?

The astro city power supplies don't have amplifiers in them--they only have large high wattage pots to attenuate the speaker level. AFAIK only the 421-8741 add-on unit actually contains an amplifier to run stereo games.

Open it and verify the pot and wiring is good, that's all there really is to it. You can even completely bypass it if you want; personally I think volume attenuation between the PCB and the speakers was a stupid choice by the manufacturers.

Model 400 5261-01 - everything looks fine and has been reflowed. I'm a beginner with understanding PCB's and components - it's puzzling why there's no sound. Want to take a look at it?

 

[scaryhours]

Mine started acting weird then soon after a spark blew out and my cab was all dead. Recap it, no luck. I had to completely upgrade to Axun's JCCBOX @axunworks for arcade monitors. Rewired everything and he also custom made me the controller panel adapters and cables to his JCCBOX. Back up running better than before. Those PSU units are old and really hard to keep them running after 25+ years.

I'm trying to keep everything original for now. Have 3 working PSU's and this one without sound.

 

[trashedcabs]

Model 400 5261-01 - everything looks fine and has been reflowed. I'm a beginner with understanding PCB's and components - it's puzzling why there's no sound. Want to take a look at it?

I mean I can... but the circuit is quite literally one single component: the volume pot. Nothing else in the power supply touches audio; the amplified audio signal literally comes straight from the game board through the harness into the pot and then out to the speakers.

With your multimeter (requirement to owning an arcade machine imo), you can test the pot easily with the resistance setting on the meter without even opening the unit. It's a 100ohm pot, so if you meter between SP+ and SP- you should get somewhere between 0 and 100 ohms. If you turn the pot, you should be able to see the value increase and decrease smoothly from roughly 0ohm to roughly 100ohm. Now if you meter between AF+ and AF- you should get the value of the pot which is 100ohm and it shouldn't change.

If the value jumps around wildly or reads very high resistance then your pot is likely bad. If one or both pairs read open circuit then likely the pot is bad or possibly there's a bad connection somewhere.

Hope this helps. It's an easy thing to look at yourself and I would encourage getting your feet wet with repairs rather than relying on sending things off.

 

[scaryhours]

I mean I can... but the circuit is quite literally one single component: the volume pot. Nothing else in the power supply touches audio; the amplified audio signal literally comes straight from the game board through the harness into the pot and then out to the speakers.

With your multimeter (requirement to owning an arcade machine imo), you can test the pot easily with the resistance setting on the meter without even opening the unit. It's a 100ohm pot, so if you meter between SP+ and SP- you should get somewhere between 0 and 100 ohms. If you turn the pot, you should be able to see the value increase and decrease smoothly from roughly 0ohm to roughly 100ohm. Now if you meter between AF+ and AF- you should get the value of the pot which is 100ohm and it shouldn't change.

If the value jumps around wildly or reads very high resistance then your pot is likely bad. If one or both pairs read open circuit then likely the pot is bad or possibly there's a bad connection somewhere.

Hope this helps. It's an easy thing to look at yourself and I would encourage getting your feet wet with repairs rather than relying on sending things off.

Thank you for the info! I'll mess with it today and see what it reads. (I do have a multimeter haha)

 

[scaryhours]

Bought a pot off eBay and going to swap and see if it fixes it.

 

[nem]

Technically, the volume knob in an Astro uses a rheostat, not a potentiometer, and the pot you bought is meant to be used as a voltage divider, not to add resistance.

Did you try to measure the resistance with a multimeter as was instructed? What did you get? Have you flipped the PSU over, are the wires even connected?

 

[scaryhours]

Technically, the volume knob in an Astro uses a rheostat, not a potentiometer, and the pot you bought is meant to be used as a voltage divider, not to add resistance.

Did you try to measure the resistance with a multimeter as was instructed? What did you get? Have you flipped the PSU over, are the wires even connected?

fixed it by luck.

Compared both units, tested the "broken" one - 95.8 down to .03 ohm

Other unit was 106.3 down to .07 ohm

Both tested fine at the AF+ and - ports.

Found this attached to the location pictured and cut it off - sound works now. What did I do?

 

[nem]

I assume it's a capacitor. The other PSUs don't have it?

 

[scaryhours]

I assume it's a capacitor. The other PSUs don't have it?

No. And I have 4 total PSU's here.

 

[scaryhours]

I assume it's a capacitor. The other PSUs don't have it?

I followed the audio trace down to that cap. It also follows the high voltage route. Took a shot and the audio works.

Any clue why someone would put that cap there? To maybe run an external audio source and mute the jamma audio?

EDIT: here's one from eBay - lower right hand corner is where the cap was installed. This unit doesn't have one either.