Qbert is driving me QRAZY.

Black Matrix

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I think I have lost my will to fix my qbert....Maybe to live as well. This yellow monkey has been on my back for far too long now. I have too much time and money invested to give up and am too frustrated to continue.

My Question: Can anyone think of any reason a Qbert PS would test working with no load and blow the fuse when I hook up a supposedly 100% working sound board. Just bought the working soundboard off a Klover and most likely promptly blew it right the hell out. No smoke or anything, just a blown fuse at first. I replaced the fuse and powered up with nothing attached to test the voltage of the power supply. Got all the right voltages.Then I plugged the PCB in and its working. Then I plug the sound board in and I get a couple pops and maybe a blue arc that looked like it came from the backside of the PS below the P3 plug. NOW, the fuse isn't blown, the LED that indicates the 30 volts is present stays on, and the 30 volts is nowhere to be found on the P4 plug. I swear this games out to get me. Any suggestions would be appreciated. My guess is a short, but I have no idea where to look. I can assume the PS's 30 volt is done for. But considering the PCB is working, and the PS is working minus the 30 volts, where should I look for the short and what might be blown on the PS, and why the hell is that damn LED still on. I swear , its mocking me. ;)
Thanks in advance
 
I think I have lost my will to fix my qbert....Maybe to live as well. This yellow monkey has been on my back for far too long now. I have too much time and money invested to give up and am too frustrated to continue.

My Question: Can anyone think of any reason a Qbert PS would test working with no load and blow the fuse when I hook up a supposedly 100% working sound board. Just bought the working soundboard off a Klover and most likely promptly blew it right the hell out. No smoke or anything, just a blown fuse at first. I replaced the fuse and powered up with nothing attached to test the voltage of the power supply. Got all the right voltages.Then I plugged the PCB in and its working. Then I plug the sound board in and I get a couple pops and maybe a blue arc that looked like it came from the backside of the PS below the P3 plug. NOW, the fuse isn't blown, the LED that indicates the 30 volts is present stays on, and the 30 volts is nowhere to be found on the P4 plug. I swear this games out to get me. Any suggestions would be appreciated. My guess is a short, but I have no idea where to look. I can assume the PS's 30 volt is done for. But considering the PCB is working, and the PS is working minus the 30 volts, where should I look for the short and what might be blown on the PS, and why the hell is that damn LED still on. I swear , its mocking me. ;)
Thanks in advance

Does your Q*Bert still have the shiny silver cardboard behind the PCB? If so, that conducts and could cause a short if it touches the PCB.
 
Yes as KM said, either the knocker or the Sound is causing it, as they are the only 2 things running from the 30V

Isolate them seperately to see which one it is

(I am an electrician), that's what we do to find faults
 
Its possible but not real likely that the transistor on the main pcb that drives the knocker could be shorted and/or the knocker coil shorted. Usually the transistor either works or it doesnt. Do you have 30v on the power supply with nothing connected? If so, disconnect the sound board and knocker and retest.
Q*Berts are not that hard to fix but you have to repair them in the right order. Always rebuild the power supply first, then reflow filter board and then move on to the other boards.
 
Oh, the things me and Qbert have been through.

To begin with, it was bought dead. But after blowing the 5 volts on the PS, and buying rebuilt one and rebuilding the power brick, I had a working Qbert sans knocker and voice.

Had a friend rebuild the coil (its all new), and also bought a new speach chip. Both failed to fix any problem. Then, the board itself developed a glitch with the background graphics. I bought the parts to repair that but because I didn't trust my ability to replace the IC sockets, just purchased one off a KLOV member 100% working.

I then had a Qbert that was working sans any voice, sound, or knocker. Were really making progress here.

I may have blown the fuse to the 30 volts the last time I messed with it so I replaced the 30 volt, tested all the voltages on the output, and re powered the game. The 30 volt blew.

So I unplugged the coil, the sound board and the pcb. Replaced the F-21 fuse IIRC. Powered up and tested for voltages. All voltages present and accounted for.

Plugged the PCB in. Games playing without sound. Plugged in the sound board, PS pops a couple times mayby arcs once on the back side and the 30 volts dies. The reason I am stumped is because the LED is still on, and the fuse is unblown. But the 30 volts is dead and something is in the game shorted. I don't think I ever even got to plugging in the new coil. And considering that I had the wire cut at the PCB to replace the pin, it shouldn't have ever shorted it in the first place. Initially, I cut the wire thinking it wasn't making connection and thats why it wasn't working. I found out you can't get the amp pins now and was stuck. I had also replaced the Q2 transister that sends the 30 volts to the knocker assembly thinking it was bad. It wasn't as I still had my problems. I have gone 10 rounds with this one, and it really has been the hardest POS I have ever tangled with. And just to drive that point home, I have a working Star Wars cockpit w/25" amplifone and an UR Firefox and both of them work.

If I were guessing, my 100% working sound board is bad(although I doubt a fellow klover would do that to another), or something has gone horribly horribly wrong with the PS, or I have the mother of all bugs in this things wiring harness. Its the only thing that makes sense for the knocker not to work when the 30 volts is present, and the reason the 30 volts is blowing up now.


but I digress. I guess, I just needed to vent. I was just hoping someone could point me to something I might not have thought of.
 
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Sound board sounds sus as you said, you have to rule it out somehow

EDIT: And bench test the Knocker maybe, straight to the 30V and see (No PCB's involved)
 
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