My Lethal Weapon 3 has all the CPU lamps out. The 8a F2 lamp fuse was blown and I replaced it last night. Upon powering the game on, the fuse immediately blew again. How would I determine if the bridge is bad?

I didn't see this guide mention how to test it. I guess could just flat out replace it without testing, but want to learn how to troubleshoot efficiently and only replace a part if it is bad and not just guess and this is my first repair dealing with bad board components.

http://techniek.flipperwinkel.nl/desega/index3.htm#lamp

The attached photo is not from my machine, it's from the above guide and included for reference.

What other component would cause this fuse to immediately blow? Would the large lamp capacitor cause the fuse to blow if it was bad, or just cause the lamps to fail?

Thanks.

image-641.jpg

Great idea. Found an excellent video testing bridge rectifiers on a Defender arcade board and one of them is the same type as on LW3.

Is it too nerdy that I can't wait to get home and test a bridge rectifier?

Impatiently waiting for the new bridge rectifier to arrive!

But I've been playing the hell outta LW3, even though I'm playing "blind" with no insert lamps on. It's going to be like a whole new game for me once the playfield inserts are lit up. As it is now, I've been learning all the shots and know what shots to hit to advance modes and scenes and score extra balls, etc.

Ok, so the new bridge rectifier fixed the playfield insert lamps. So that's great.

But the backbox lights are still out, except the flashers. I replaced the fuses on the PPB that the manual says is for the backbox. One of the connectors coming from the backbox looked like it had a brown spot on a pin, so I clipped the wires and butt connected them to make sure it wasn't a bad connector.

What should be checked next for the backbox lights?

Thanks!

Found a helpful post on another forum, figured I would post here for future reference for anyone else. I'll work on this tomorrow.

"There are way too many connectors in the design of the Data East GI Circuitry, and as a result, the reliability of the whole GI circuit is rather bad, as you well know at this time.
The best way to fix the GI lights is to systematically go through the entire system from the transformer to the light bulbs and replace any and all connectors, fuses, and bulbs that are bad.
First start at the transformer in the bottom of the cabinet. There should be a connector with four large yellow wires on it. Make sure that you are reading 6-7 VAC at that connector and that that connector is in good condition (not discolored and brittle). Now move to the connector that will be in the upper right of the power supply, typically this connector is on a "pig-tail" of 4 yellow and yellow-white wires that have a connector at one end and are soldered to the power supply on the other (CN9). Measure the voltage of the GI power at this point, you should be getting the SAME voltage (within 0.1 volt or so) as the previous measurement, if you are not, then there is an issue with this connector or the previous connector, replace BOTH SIDES of the connector. The next link in this chain is the relay on the power board. You should be able to test this in the Diagnostics menu, if not, during attract mode this relay is "on" and the voltage at the output of this relay should be the same (within 0.1 volt or so) as the previous measurements. Next in the chain is a 9 pin in-line connector (CN8), this one has, brown, yellow, purple and green wires on it. Replace BOTH the connector on the board and the connector on the wires, if you only replace one, you are not fixing the problems that you have. This connector typically gets very hot and will fail over time. The next connector is on the PPB Board, this is the J5 connector, replace both it on the board and the mating connector on the wires. Then on the PPB Board, replace the fuse holders for F1, F2, F3, and F4, and put new fuses in them. These fuse holders were very poor and will often crack and cause contact to be lost to the fuses. There is one last connector in this string, and it is in the cable harness to the backbox. I have yet to see an issue with the backbox connector, but you will want to look at it if the backbox lights are not working. At this point the voltage that you should read at the bulbs should be almost the same as the one that you measured at the power supply CN8.
Now that all of the connections and fuses are new, the GI should be shining so brightly that it blinds you, provided that you have good bulbs in the system.

I am sorry if this is a little long-winded, but after having to do this to EVERY data East machine that I have owned, I have come to the conclusion that the only way to make the Data East GI circuit bullet-proof, is to shotgun the whole thing. At the very minimum I replace CN8 (both sides), J5 (both sides), and all the fuse holders on the PPB in the GI system. Once this is done, it will last the rest of the life of the pinball machine in home use."

Visual inspection shows the J5 connector on the PPB has two burned connections. Will perform the voltage testing as described above, but hopefully this will just be replacing that connector for a short term fix. Then can set aside the to replace the pins of the boards.