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Blast City PSU Help

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BlastRugi

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Got an issue with my Blast City PSU. My Blast worked fine with every jamma game I tried on it, but I noticed the 5v rail was running a bit low at 4.4v when a game was plugged in. Tried out my naomi 2 and sure enough it wouldn't boot.

I bought a cap kit, recapped it with no issues, and now it wont boot up any games and the fan wont spin up. The monitor sounds like it works fine (with the iconic 15khz sound) but I cant get the monitor OSD controls to come up, and the 5v pin on the jamma harness reads barely 3.5v with a board plugged in.
I double checked all the soldering, double checked the orientation, and double checked that the caps are in the right place. I also made sure to buy the caps from a reputable source (arcadepartsandrepair's website)
I provided photos as well, though they might be a bit blurry so let me know if I should take a closer photo of anywhere.

Anyone know where I should go from here?

Edit 1: Tested the 5v pot, seems to adjust resistance just fine with a multimeter, but the output does not appear to change when I have it plugged into a board. Tested all the caps solder joints for continuity, and everything is making good connection.

Edit 2: Good news, well sort of. I tried pretty much everything I could and it still didn't work, so I went ahead and started to put the old caps back in. One of the pads ripped off on C39, but luckily it was on the opposite side and wasn't an issue. I got about halfway through, tested it, and the game now powers up and I am back to the original 4.4v with a game in. There was no sound and the fan still doesn't spin up, so I am gonna finish putting in the old caps for the 12v rail and I *think* I should be good. Will update accordingly
 

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Maybe @Kidkaos would know since it seems like he works on these machines a lot. For what it's worth the only possible solutions that I could come up with are either you need to turn the 5v in knob to adjust the 5 volts. I'm thinking that the new caps are what knocked down the volts to 3.5. I could be wrong though, but it would be worth a shot to adjust your 5 volts on the power supply. The other solution that I would be thinking about is maybe wrong values on the capacitors? I've bought and still do from arcadepartsandrepair.com and haven't had a problem with any of their cap kits so I don't think that this would be the problem unfortunately. I'm interested if Kidkaos has anything to that he suggests as well.
 
kayzp4ul said:
Maybe @Kidkaos would know since it seems like he works on these machines a lot. For what it's worth the only possible solutions that I could come up with are either you need to turn the 5v in knob to adjust the 5 volts. I'm thinking that the new caps are what knocked down the volts to 3.5. I could be wrong though, but it would be worth a shot to adjust your 5 volts on the power supply. The other solution that I would be thinking about is maybe wrong values on the capacitors? I've bought and still do from arcadepartsandrepair.com and haven't had a problem with any of their cap kits so I don't think that this would be the problem unfortunately. I'm interested if Kidkaos has anything to that he suggests as well.
Click to expand...
Forgot to mention! I did try the 5v adjustment pot, and it does not do anything, like at all. No matter which way I turn it, it stays steady.
 
Can you get a close up picture of this?

Also do you notice anything get abnormally hot really fast? Maybe some of the big metal heat sinks

1000018882.jpg
 
Seems like a bit of old flux. And I do not, but I can check again when I get home from work
 

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You can try reseating the PSU box (pull it out and push it back in). If the PSU box is not making good contact with the cab connector, you can have all sorts of issues.

Did you make sure you put in same value caps that you took out? If you're not sure, then you'll need to write down here what you have installed.
 
nem said:
You can try reseating the PSU box (pull it out and push it back in). If the PSU box is not making good contact with the cab connector, you can have all sorts of issues.

Did you make sure you put in same value caps that you took out? If you're not sure, then you'll need to write down here what you have installed.
Click to expand...
Tried repeating it a few times and I cleaned the pins with some alcohol. I saw an old post about cracked joints on the IO out so I will try that as well, but I'm not sure why it only stopped working now.

As for the values, I am very confident they are correct. I triple checked to make sure the right values are in the right spot and the right direction.

If all else fails I'm probably gonna put the 5v caps back in. Does anybody know which caps are connected to the 5v rail?
 
Try cleaning the connectors on the psu and cab side, use deoxit or something like that.

You can try checking for cracked joint and reflow those.

Is there a pinout of the PSU PCB and its connectors. I have only found the schematic for the cab, but not the internal pcbs on the psu case.
 
Derick2k said:
Try cleaning the connectors on the psu and cab side, use deoxit or something like that.

You can try checking for cracked joint and reflow those.

Is there a pinout of the PSU PCB and its connectors. I have only found the schematic for the cab, but not the internal pcbs on the psu case.
Click to expand...

I had a similar issue with my Blast PSU and I did what Derick2k suggested above. After a recap, I reflowed every solder joint even if it was shiny, then I cleaned the connectors with IPA and then used deoxit before plugging everything back together. After that, solid every time. Good luck!
 
Derick2k said:
Try cleaning the connectors on the psu and cab side, use deoxit or something like that.

You can try checking for cracked joint and reflow those.

Is there a pinout of the PSU PCB and its connectors. I have only found the schematic for the cab, but not the internal pcbs on the psu case.
Click to expand...
Cleaned and polished every contact with alcohol, then deoxit, and reflowed pretty much every pin connected to the 5V rail and still nothing. CRT powers up, my pi flashes the low power symbol, and the fan wont spin up on the psu. Im gonna go ahead and start putting the old caps back on one by one and see if that fixes it, starting with the 100uf 25v cap connected to the fan header
 
Still ended up with a non-working PSU. It seemed to work for a second but now it is back to only powering up the monitor and nothing else.
Does anyone have a recommended board repair person that I can pay and send this off to?
 
The caps would not be the problem unless they were installed backward. If so, you have noticed signs :D

I would tell you to try and inject sound, to see if the sound amp is working fine.

If the fan is not spinning might indicate that you also dont have voltage on your 12v line. Can you test for power at the fan connector? Is it one of those fans that has a speed sensor? Maybe its bad and it tells the PSU not to power up.

Wish I could help you out more, if I had an schematic of the psu PCB itself I would point you better at what to check. Just so many things that it could be.

If anyone has a defective blast city psu, I would love to buy it, just want to see how they put this thing together.
 
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Maybe unplug everything and only test the PSU? Just throwing ideas out there...
 
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