No power

[alejandromadera]

Won this on eBay ($15)... seller only told me it "wasn't working". Got it home... checked the voltage from the transformer and it seems fine. Plugged it in and... nothing. No lights, no sound, nada.

Hey... look... a fuse. Took it out and it 'looked' bad... metered it and it IS bad.

Here are my questions:

1. Where might I find such a fuse?
2. Are there likely to be more things 'bad'... in the power supply module for example?
3. There is a module hanging loose in back also (see picture). What is it?

I know less than nothing about these things so any help is appreciated.

[dattia]

It would be nice if the fix turned out to be an inexpensive fuse! Sorry, I cannot help with this issue, but I am sure that someone 'in the know' will take a look and help you out.

I just wanted to say Good Luck!

[pinball wizard]

you didn't show a picture of the fuse,but if you have a radio shack or other electronic store near you ,they may be able to help you with a replacement .

[alejandromadera]

OK... here's a picture.
I think its an 5x20mm "T8A" 8A fuse... slow blow maybe?

Sorry about the handmade measurements. The only ruler I could find was clear and I didn't think it would show up too well in a photo.

so... no one has ever had to replace a fuse in their Pachinko?

[compirate]

Kinda unusual to blow one in the power supply. Should be able to get that in a Radio Shack or perhaps auto parts/hardware store.

I see Radio Shack has 6.3 amp in that size. Would think that would be good enough for a test, really shouldn't pull 8 amps, even in 'bells and whistles' mode. Is there anywhere on the back, printed in white on one of the control boxes a number with 'VA' after it? Divide that number by 24 should be the amps the game will draw.

The box that's hanging down is probably the stepper motor controller for the shooter. Have to see if there's a place for it to hang on back there somewhere.

[alejandromadera]

Kinda unusual to blow one in the power supply. Should be able to get that in a Radio Shack or perhaps auto parts/hardware store. I see Radio Shack has 6.3 amp in that size. Would think that would be good enough for a test, really shouldn't pull 8 amps, even in 'bells and whistles' mode.

Yep... Radio Shack had some 6.3 amp fuses and I stopped on my way home from work and bought some.

Is there anywhere on the back, printed in white on one of the control boxes a number with 'VA' after it? Divide that number by 24 should be the amps the game will draw.

No... I don't see any such markings.

I replaced the fuse and turned it on... nothing... no sound... no flash... nothing.
Pulled the fuse and it was blown.
Replaced it again... disconnected all the connectors from the power supply and turned it on again. Turned it off and checked the fuse.. blown again.

I'd say bad power supply.
What next?
Does anyone repair these?
Are there replacements available?
Should I give up and part it out?

[alejandromadera]

Pictures of the defective unit. As I said... when everything is disconnected, and power is applied, the fuse blows.

[compirate]

Someone may have sparked it (plugged it directly in to 120VAC without using a transformer). Could have blown a diode or similar component (bridge rectifier), which would cause the fuse to blow. Got any electronics knowledge?

[alejandromadera]

Someone may have sparked it (plugged it directly in to 120VAC without using a transformer). Could have blown a diode or similar component (bridge rectifier), which would cause the fuse to blow. Got any electronics knowledge?

Yeah... I figure that's what happened... they may have plugged it straight into the wall. I guess I will try and get the plastic enclosure off the power supply and shotgun it. I have a fairly good grasp of electronics theory but am out of practice to be sure.

Thanks for the assistance and, if you should think of anything else that might help, I am all ears!

[daverob]

First thing to look at when the main fuse blows instantly (ok second after disconnecting the outputs, but you've already done that!), is the crowbar device across the 24VAC input.

This is a small device that usually looks similar to a diode and will be located near the fuseholder. It's purpose is to go short circuit if the machine is plugged directly into a 100V outlet and blow the fuse instantly, hopefully protecting the rest of the electronics from any overvoltage damage. It's not resettable and if it has tripped will need to be removed or replaced.

Next check is the bridge rectifier diodes, if any of them go short circuit, the fuse will blow instantly on power up, and they can easily be checked using the diode test on a multimeter.

If these checks fail, then usually the best bet is to shotgun all the semiconductors on the board.

[alejandromadera]

First thing to look at when the main fuse blows instantly (ok second after disconnecting the outputs, but you've already done that!), is the crowbar device across the 24VAC input.

So... I freed the PCB from it's plastic cocoon but I can't really tell which components might be part of the protective circuitry. Here are some pictures along with an image of the backside (electronic components identified) in the hopes someone can give me some more explicit guidance.

If these checks fail, then usually the best bet is to shotgun all the semiconductors on the board.

I am willing to replace all the likely affected components but I have two main issues to resolve:
1. Which components are they?
2. What are their values.. how can I figure that out without a schematic?

-Allen

[compirate]

From a quick search on the web, the ZNR is a surge protector 'ZNR Transient/Surge Absorbers'

I'd check that ZD - Zener Diode too.

Not sure what the DSP's are, but look to be really the only other thing that would cause a problem.

I could be wrong, but I'm getting "Discrete Semiconductor Product" for those DSP parts. Could be a form of diode for other protection.

[daverob]

How's your soldering? If you are able to safely remove the big choke L2 (big coil of wire next to the power switch), then remove this completely (after making a note of it's orientation so you can replace it later!) and see if the fuse still blows. If it still blows then you know that the fault is with one of the components on the switch side of this choke. If not then you need to start looking at the bridge rectifiers.

If you're not confident enough to remove the choke without risking damage to the choke or the PCB, or the fuse still blows with the choke removed, then get a multimeter set to diode test and measure across ZD, try the test once then swap the multimeter leads to the opposite pins and repeat. Do the same test with ZRD. If either ZD or ZRD measures short circuit in either direction, then unsolder one of it's leads and try powering up again to see if the fuse still blows.

DSP1 & 2 are just noise suppression, it's unlikely that their failure could cause a fuse to blow (both of them would have to fail short circuit at the same time for the fuse to blow, and it's likely that any event that would cause one of them to fail short circuit would cause the fuse to blow before the other one has a chance to fail). You might want to try unsoldering one lead from these and try powering up again, just to rule them out, but I wouldn't be holding much hope that this would fix anything.

If none of this has worked so far, or the fuse did not blow with the choke removed, then you need to check the bridge rectifiers. There appears to be three of these (the rectangular boxes to the left of the fuse. Using diode test on the multimeter, check each pin to the other three pins (with leads both ways round) and compare the readings to those that you get on the other two bridge rectifiers. If any leads measure a sustained dead short circuit or are significantly different from the other two bridge rectifiers, then you have found your faulty component. Note that you might get brief short circuit readings while the capacitors charge up, but these will return to a normal reading if you hold the leads on the pins for a few seconds.

If none of this manages to find the problem, then post back and we'll let you know where to go from here.

[alejandromadera]

Wow... thanks for such a detailed response. I read, and understood, your suggestions and I will do that this weekend. Once I have done so... I will report back. Wish me luck!

Thanks again... to all of you!

[dattia]

Good luck! You got advice from the best...daverob is our resident genius!