Dungeons & Dragons Check Field Fuse/FU-1 Error

(Topic ID: 207183)

Dungeons & Dragons Check Field Fuse/FU-1 Error


By rmmdam

6 months ago



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  • 10 posts
  • 2 Pinsiders participating
  • Latest reply 5 months ago by wayout440
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Molex1_LI (resized).jpg
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#1 6 months ago

I have a D&D pin (6803 MPU) that keeps freezing and displays "Check Field Fuse or FU-1". Both fuses check out fine. I have removed both fuses and performed a continuity check on them. This occurs most often when one or two balls are held in the left and/or right teleport. The game will often reset if I lift the playfield and remove and reinsert the fuses. I have seen older posts about this issue and have tried the various recommendations without success. I have tested the ball trough Opto boards, and even replaced them with brand new boards. I covered openings into the ball trough to prevent light leakage. I reflowed the pins on the power board which remedied an intermittent power loss problem, but it did not fix the fuse error. Checked all voltages on the power board and MPU board and they were all within range according to the manual. I subsequently replaced the power board with a brand new power board. I checked the fuse holders and they appear to be sound and the solder connections do not appear to be cracked or cold soldered. Checked the pin solders on the MPU and they appear to be ok. When I run a switch test with the key pad, I get the message that outhole switch left, middle and right are closed and the switch test stops at that point. This message occurs when all balls are in the trough. Should these switches be normally closed when there are balls in the trough? Is there anything else I should try? Any suggestions will be greatly appreciated! It's a fun fast game when it works!

#2 6 months ago

Field fuse F1 is under playfield near lower flippers. Have you checked for DC voltage at each side of the fuse? The fuse itself could be good, but need to know if voltage is actually getting to this part of the circuit. For some reason the MPU doesn't think it is.

Switch test indications are normal

#3 6 months ago

Thank you. I will check the voltage at the fuse. I assume it should be 43vdc when it is operating correctly and lower when it is in error mode? Also, is there a chance of a faulty MPU cable connector or chip? I did inspect the pin solders on the MPU and they appeared to be ok. If the voltage is low, what could be causing it? The error message occurs most often if there are balls in either of the teleports waiting for multiball to be triggered.

#4 6 months ago
Quoted from rmmdam:

Thank you. I will check the voltage at the fuse. I assume it should be 43vdc when it is operating correctly and lower when it is in error mode? Also, is there a chance of a faulty MPU cable connector or chip? I did inspect the pin solders on the MPU and they appeared to be ok. If the voltage is low, what could be causing it? The error message occurs most often if there are balls in either of the teleports waiting for multiball to be triggered.

Hard for me to determine at the moment. Also not familiar with the game. The teleports use solenoids?....do they work in solenoid test?

#5 6 months ago

Yes, there is a solenoid that captures the ball in the teleport and then pops the ball out when multiball is triggered. They do work in solenoid test.

#6 6 months ago

I've gone back and read some other threads that suggest this is a switch issue. Try going back to this again. This time take all balls out and perform the switch tests.

#7 6 months ago

Good idea, I will try that. I also found a Molex connector on the wire harness connected to J3 socket on the power board where all the pins protrude at different depths in the Molex and one is so deep that it is preventing the the plug from seating firmly in the J3 socket. Not sure what J3 powers in the play field, but if one of the pins in the plug is not making good contact, could that cause a Check Fuse error? I need to trace that jumper in the schematic to see what it is powering. If it could be the Molex plug causing the problem, I don't know how to reset the pins in the plug to the proper depth. They won't budge. As you may guess, I am really new at this-thanks for your patience!

#8 6 months ago
Quoted from rmmdam:

Good idea, I will try that. I also found a Molex connector on the wire harness connected to J3 socket on the power board where all the pins protrude at different depths in the Molex and one is so deep that it is preventing the the plug from seating firmly in the J3 socket. Not sure what J3 powers in the play field, but if one of the pins in the plug is not making good contact, could that cause a Check Fuse error? I need to trace that jumper in the schematic to see what it is powering. If it could be the Molex plug causing the problem, I don't know how to reset the pins in the plug to the proper depth. They won't budge. As you may guess, I am really new at this-thanks for your patience!

Sounds like a poorly crimp/bad connector....almost sounds like it needs replaced. Can you post a pic of it?

#9 6 months ago

Here is the Molex plug. If you need a different angle, let me know. The crimped pin in the third socket down on the right sticks out too far. There appear to be hundreds of Molex connectors on their website. How in the world do you pick the correct size for the wire and shape to fit the socket?

Also, I ran a switch test without balls in the ball trough and all switches are open. Only getting 0.4V across the field fuse holder both with the fuse in and fuse out and when the game is in error mode and also working properly.

Molex_LI (resized).jpg

Molex1_LI (resized).jpg

1 week later
#10 5 months ago

Molex MLX 42002 series

Quoted from Atari_Daze:

The board connectors I ordered from Digi-key, from Molex, MLX™ 42002 series, were an exact swap. I swapped the board headers and mating connectors for the 9 (back box) and 15 pin (controller) and the display issue has been corrected! The 9 pin did have an indexing post that needed to be snipped off but aside from that, it was an easy, fast fix.
Thanks to those who helped me track down the parts needed for this fix, I love this site!

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