(Topic ID: 91393)

System 1 Blows 69v 1/4A fuse- FIXED

By btw75

4 years ago

Topic Stats

  • 19 posts
  • 3 Pinsiders participating
  • Latest reply 4 years ago by pdman
  • No one calls this topic a favorite


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#2 4 years ago

First, start here:

If you have A1J3 disconnected, does the fuse still blow?

Let's say you just have A2J3 from the PS to the displays connected. Does the fuse blow?
OK, with just power supply(A2J2) to CPU Board (A1J1) connected, does the fuse blow?
How about with just A1J3 connected to the CPU PCB. Does the fuse blow?

#4 4 years ago


That's what I'm asking. You say you need ALL 3 plugged in to make the fuse blow?
So any two combinations of connectors or a single connector plugged in does not blow the fuse?

So if power supply (A2J3) to displays and power supply(A2J2) to CPU Board (A1J1) are connected
the fuse doesn't blow? If you connect A1J3 connecting CPU board and displays does the fuse then blow?
BTW , do all your connecting and disconnecting of connectors with the Power OFF.

You may have a short somewhere also. Have you measured the +60 and +42 VDC for the displays to ground for a short? You also mentioned that you think the connectors may be mispinned. For that you could do a continuity check of A1J3 to the display connector.

If the displays are NOT Connected, does the fuse still blow when all three of those connectors are connected?

BTW, what System 1 pin is it?

#8 4 years ago

10k is fine.
Have you checked all of the three connectors to make sure that they are pinned correctly.
If A1J3 is disconnected what measure do you get for the +60VDC and the +42 VDC?

#11 4 years ago


Can you coin up, start a game?
Are all your displays out, even the credit/ ball display?
Are you getting the +4VDC and the +8VDC from the power supply?

Do you have at least one display that you know works?
Also the displays sometimes need to be degassed as explained in the System 1 Repair Guide.
I suggest degassing at least one display and see if that display works.

#13 4 years ago

Yes, the pascal all in one is one terrific PCB. Good idea on using that to troubleshoot. After I fixed my system 1 Pins, I always upgraded either with Pascal's CPU or All in One.
I did a post on how I repair the original System 1 PS. It's a pain to have to take out the pass transistor and then put in a new one and if you still have issues you need to rip it out again. My solution to this is simple. I'll look for the thread and post the link here.

#14 4 years ago

here's the post on fixing the system 1 power supply.


1 month later
#17 4 years ago
Quoted from btw75:

Resolving this thread: I brought out the scattergun and just bought a GPE & Ni-Wumph CPU board.

So it's FIXED - Now NO DISPLAYS! ?? So is it fixed and the displays don't work or they do work?

#19 4 years ago

great, enjoy your pin

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