Qbert Power supply & wiring Help - Q*bert

Steve Moerke

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Well I have 2 Qberts, why because the 1st machine I bought didn't work and then a week later I got a working machine (typical story). Anyways, I am attaching pictures of the working machine boards and the non-working machine boards.

Non-working machine serial # 2654, sticker on the board says 1985. I was told it blows fuses. I plugged it in and it burnt the wires coming from the brick in the bottom and I can see a burnt connector from the top board on the left to a burnt connector on the top board on the right. I also can see burnt looking resistors on what I believe to be the power supply (top right)

Working Machine serial #401, year? I also can see burnt looking resistors on what I believe to be the power supply (top left) but the machine is working fine.

Why do the 2 board sets look completely different?

I see there is burn on the resistors on the power supply of the working machine witch leads me to believe it is close to death because it is the same burn on the resistors of the non working machine.

If I am to buy the new Qbert power supply rebuild kit will this work on both machine board sets or just 1 of them? Does any body out there recommend who I should send the non-working boards to for repair? What do I do about the burn wires from the brick to the boards?

If it is to much to type my options feel free to PM me your phone number and I will call for information.

Thanks,

Steve
 

Attachments

  • Qbert does work serial #401.jpg
    Qbert does work serial #401.jpg
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  • Qbert Doesnt Work 1985 serial #2654.jpg
    Qbert Doesnt Work 1985 serial #2654.jpg
    96 KB · Views: 43
You have an early build machine and the boards were layed out different on them. The one without the filter board is the early machine.
All the boards are the same, just mounted in different locations.
I sell the power supply rebuild kits or I can rebuild them for you. This is the first step in repairing a qbert. Also, the filter board will need to be reflowed as they always have cracked solder joints.
 
just in case you don't know much at all about these machines - there are 3 main boards: the CPU (or logic) board; the sound/video board; and the power supply. on most of the machines, there is a fourth smaller one which is a filter board. as Riptor says, the lower numbered one you have is an early build, which doesn't have the filter board. on that early build one (the one you say works), the logic board is on the bottom, the sound/video is on the upper right, and the power is on the upper left. on the newer one, the logic board is still on the bottom (but rotated), the power is on the upper right, the sound/video is on the upper left, and the filter board is above that.

you can see that in the newer board, one of the big capacitors is missing. these are 2200 uf, 75 V caps. there is also a missing resistor to the right of the diode where the burn marks are. that's obviously at least part of your problem. burning out the diode and/or the resistor to its left (not the missing one) which are just above where that missing cap should be is a common problem for these power supplies. it is often associated with other burnt out resistors and sometimes burnt out power transistors (the big silver ones attached to the heat sink). in fact the resistor that is to the left of the diode (right next to the heat sink) is not an original - the originals are wire-wound ceramics with cement and the one in your picture is definitely not that. there are other indications somebody tried to fix the board in the past (like the connector at the bottom left, which should be right on the board but is connected with yellow wires). no telling what they did to it.

four options for you: 1 - buy a working power supply (they go for roughly $70 on ebay - or somebody on these forums may give you a better deal); 2 - have somebody else fix it for you (like Riptor); 3 - rebuild it yourself; 4 - buy a replacement from arcadeshop.com which is not original but will also work (and costs about $50).

if you do (3), be prepared to replace all the electolytic caps, some of the big resistors, the diode (use a 24V zener instead of the 30V that's in there), and the two power transistors (the 2N5879 for which a replacement is the NTE180 and the 2N3055 for which a replacement is the NTE130).

for the two q*berts i have, i did (4) for one because it didn't have the board at all (and i'm not that much of a purist), and (3) for the other. you may find a different solution, especially depending on how comfortable you are with mucking with this kind of thing.
 
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