(Topic ID: 244952)

TECH: Zac Time Machine Connector CN1 Burning


By schudel5

8 days ago



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  • 7 posts
  • 3 Pinsiders participating
  • Latest reply 8 days ago by HHaase
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#1 8 days ago

So I have a Zaccaria Time Machine that I've had for several years. When I got it it had some burned connectors on the power supply board and I replaced all of them with .156 headers and trifurcon connectors. Just a few days ago I could smell a slight plastic burning smell coming from the game. Opened it up and pins 9-12 on CN1 were burned to a black crisp. These 4 pins supply 6.5VAC to the AC legs of a bridge that then supplies 5VDC for use in the game.

The circuit is simple. The transformer has multiple taps with wires with different voltages going out. They took 2 wires in parallel from each side of the tap for the 6.5VAC. One side goes through connector CN1 pins 9 and 10 and the other side goes through pins 11 and 12. Pins 9/10 feed a 15A fuse (F3) then connects to the A/C side of a bridge.

So pins 9/10 and 11/12 on that connector were burned bad. The fuse clips for F3 were tarnished. The game worked perfectly with no issues just had that burning smell.

I removed CN1 and replaced it with a new .156" header from pins 1-8. I then took 18 gauge wires and soldered them directly to the solder pads on the board where header pins 9/10//11 and 12 were supposed to go. I put a square 4-pin Molex 0.093" connector on the end of the wires so you can still disconnect everything. I replaced the fuse clips with new high current clips a new 15A fuse.

The game is still working fine, but the wires get warm. The connector seems fine but the fuse gets so hot you can't touch it. It doesn't blow the fuse. I put a clamp-on ammeter to measure both sides going to the bridge and it varies from 9A to 15A (jumps around) during attract mode.

What would cause this issue? Is it normal? I attached a picture of the schematic and there's nothing there I can see that's causing this. Like I said the game works fine. The fuse is in tight and right now it's shiny but I'm sure the heat will change that over time.
Zac.png

#2 8 days ago

Could be a bad rectifier, or something else drawing a huge load through the connector.

Any sign of heat stress on CN2, CN3, CN4?

#3 8 days ago
Quoted from HHaase:

Could be a bad rectifier, or something else drawing a huge load through the connector.
Any sign of heat stress on CN2, CN3, CN4?

Those connectors are on the output of the bridge and they are fine. The test points are good, the connectors are fine and not hot. It's just the AC input to the bridge. A bridge typically opens and then you get no output voltage or it shorts and blows the fuse immediately. This does neither except the connectors and fuse gets really hot. It's not drawing a huge load because the fuse isn't blowing. That's what's weird.

I suppose I can solder in a new bridge and see if that changes anything. Not much else it could be.

#4 8 days ago

That's my thought as well. But I've seen bridges fail in odd ways, depending on how they fail. That and fuses are only 'close' to their rated load. So it may be drawing right at the amperage rating, or even slightly above, but not blow the fuse.

-Hans

#5 8 days ago
Quoted from schudel5:

These 4 pins supply 6.5VAC to the AC legs of a bridge that then supplies 5VDC for use in the game.

For a moment I thought you meant 5VDC for the logic boards
It's 5 volts for the feature lamps. I count a total of 92 feature lamps in the head and playfield schematics.

#44 incandescents draw 0.3 amps each so if there's many lamps that are on, that's a lot of current draw.

CN3 and CN4 are sharing the output load - the weak point in that circuit is connector CN1.
Disconnect CN3 to the playfield and see how much difference it makes.
The 10 amp KBPC1005 bridge at P3 seems underspec to me.

#6 8 days ago

Yes it's for the lamps, but I did read somewhere where the Gen2 Zacs use a signal from the GI circuit to initially boot the game. I think on Clay's repair guides I read that. I'll drop the backbox or playfield GI connector and see if this helps. Thanks.

#7 8 days ago

I was thinking the same thing too, that this was the logic power.

If it's the lamp power, it's very possible it's drawing a huge pile of current if there are any shorts at a lamp socket or something on the interface board.

-Hans

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