I am having some problems trouble shooting the solenoids on my Bally Lost World. So far I am experiencing:

- A blown fuse ( I think during power-on?) under the play field.
- While in test mode the coin door solenoid and flippers "Pull in"
- When the machine is powered on the "Knocker" (solenoid in the cabinet) energizes
- There is a pretty loud hum coming from the speaker

And some other observations...

- The rectifier board was replaced with a rottendog by a previous owner and all test points are within spec.
- The solenoid drive board appears to be in good shape. No signs of burnt or blown components.
- Some of the solenoids had been cut. I experienced the same symptoms when they were cut and when I soldered them.

I'm not really sure where I should be focusing my efforts at this point. Any advice would be much appreciated. Thanks!

Also, as an aside, I created another thread about what I thought was a rectifier issue on the same machine several months ago. Is there some way to link back or move the conversation back to that thread? Thanks again.

The MPU is in pretty nice shape. Im sure all of the connectors would benefit from being replaced. I have replaced the J3 connector on the rectifier board.

What setting should I have on my DMM? Test with the machine on or off?

I am pretty sure it stays energised. I havent kept the machine on more than a minute or two while I've been trouble shooting.

I'm a bit confused with this particular part. There is only one black lead, right?

I did test the other spots. There were three that seemed to give odd readings relative to the rest. I designated "left" as being the top most side of the SDB while mounted in the headbox and "right" as being the bottom most side. I have not had the chance the pull up the schematics and see which ones go where.

I tried to attach a screenshot of the excel doc I made with the DMM readings but the upload failed. I uploaded a pic of the screenshot. Not sure if the numbers are legible. Im making this post on my mobile device.

Most transistors were 1.0 and .3 while the ones out of range were 3+ and 0.

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No worries. Q3 goes to the "knocker" solenoid. I haven't check the others yet.

No. I bought the game in its current condition. The previous owner got it as a package deal and was not interested in it nor did any troubleshooting to my knowledge.

I like this style of troubleshooting. I definitely would prefer to check off all the easy troubleshooting before breaking out the soldering gun. I haven't had the chance to do a bottom-up approach, starting with the rectifier, yet. I did unplug J2 from the SDB though (it supplies...the flippers, I think? But more specifically the "Knocker" solenoid.) As expected the knocker didn't energize but I also lost the ability to enter the solenoid test mode

I actually came across another thread on here a few days ago where someone had an issue with their Bally and described the (near) exact symptoms I am experiencing. Turns out it was just a loose pin on a connector. I got my hopes way up that that would be resolve my problems. Alas, it did not.

And on that note, I am slowly the going through and replacing all (female) connectors and pins to the rectifier and SDB. So far though the rest of the old connectors seem pretty snug and as best as I can tell look relatively clean. There's not visible corrosion like in your image. That's not to say that there isn't any there though. But for the most part they are snug and clean-ish looking.

Here are a couple photos of the MPU.

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