Post by thephantombrain on Nov 20, 2020 15:16:28 GMT
I'm new to jukeboxes but I have some electrical troubleshooting skills from a previous occupation. If anyone could help me find the proper fix for my Rowe MM-4 issue it would be great.
When the selector switches are pressed the latch coil releases the buttons, the search unit wipers turn and the corresponding pins are pushed out the back but that's it. The magazine never runs during normal operation which in turn never allows the stop switches to interact with the pins. Now, if I manually put the scan service switch to scan and then all the way back up to on, occasionally, a record will get played but this does not happen every time for whatever reason. After hours and hours of familiarizing myself with the component locations and sequence of operation up to the point of the failure, I think I have narrowed the problem to a very minor window of possibilities. (Hopefully)
The sequence of operations in my service manual says "When the scan coil was energized, it tripped the scan control gear, closing the scan switch"... then later the document says the scan switch is supposed to energize the magazine detent coil leading to a chain of events that turns the magazine. Here's what I discovered - the scan coil does get energized for a second maybe less, which does trip the scan control gear BUT the scan switch does not get pushed. The little white lever never gets hit by the scan control gear to push the scan switch button. As a matter of fact, even if I reach in there (power off) and manually lift the scan control gear as far as it will go, the lever still won't press the scan switch button. I've also read that the stop switch can be moved closer to the lever but it appears as if it's already as close as it will go.
Here's something that's even more strange to me. The wiring diagram shows that scan switch with a r/w wire connected to COMM (or common) and a g/w wire connected to NC (or normally closed) and nothing connected to NO (or normally open) which is how it's currently wired. With the power on, I have around 26 volts present at COMM and nothing at NC if I push the button manually nothing happens but if I run an alligator jumper from COMM to NC the magazine begins to to turn etc. Does anyone have any ideas?
If the voltage is already passing through normally closed contacts which it isn't (and I suspect a faulty scan switch), why then would the button need to be pushed to open those contacts? Wouldn't opening the NC contact do the opposite of what the machine is trying to achieve? Opening the NC contacts would actually interrupt power to the magazine detent switch, right?
When the selector switches are pressed the latch coil releases the buttons, the search unit wipers turn and the corresponding pins are pushed out the back but that's it. The magazine never runs during normal operation which in turn never allows the stop switches to interact with the pins. Now, if I manually put the scan service switch to scan and then all the way back up to on, occasionally, a record will get played but this does not happen every time for whatever reason. After hours and hours of familiarizing myself with the component locations and sequence of operation up to the point of the failure, I think I have narrowed the problem to a very minor window of possibilities. (Hopefully)
The sequence of operations in my service manual says "When the scan coil was energized, it tripped the scan control gear, closing the scan switch"... then later the document says the scan switch is supposed to energize the magazine detent coil leading to a chain of events that turns the magazine. Here's what I discovered - the scan coil does get energized for a second maybe less, which does trip the scan control gear BUT the scan switch does not get pushed. The little white lever never gets hit by the scan control gear to push the scan switch button. As a matter of fact, even if I reach in there (power off) and manually lift the scan control gear as far as it will go, the lever still won't press the scan switch button. I've also read that the stop switch can be moved closer to the lever but it appears as if it's already as close as it will go.
Here's something that's even more strange to me. The wiring diagram shows that scan switch with a r/w wire connected to COMM (or common) and a g/w wire connected to NC (or normally closed) and nothing connected to NO (or normally open) which is how it's currently wired. With the power on, I have around 26 volts present at COMM and nothing at NC if I push the button manually nothing happens but if I run an alligator jumper from COMM to NC the magazine begins to to turn etc. Does anyone have any ideas?
If the voltage is already passing through normally closed contacts which it isn't (and I suspect a faulty scan switch), why then would the button need to be pushed to open those contacts? Wouldn't opening the NC contact do the opposite of what the machine is trying to achieve? Opening the NC contacts would actually interrupt power to the magazine detent switch, right?
