MM5 cancel credit issue

[mrdavidj]

Hi everyone,
I've been trying to help a friend who has an MM5 (I'm a Seeburg guy with only a little Rowe experience).  The original problem was it wouldn't take any selection (making a selection with a valid credit did nothing-the start solenoid almost never actuated).   I also note the latch solenoid was previously removed and is absent - the machine worked well prior with it absent so I don't suspect this is related, but I mention it it to add to the picture.  After reading the manual and speaking to a few Rowe folks, it sounded like a cleaning of the selector was in order.  I removed the selector, and cleaned the switches, and reinstalled.  A minor victory in now at first startup, a selection can be made and the mechanism plays.  Watching the sequence and comparing to the sequence in the manual (starting at 3-7), it seems the credit should be removed in order for the next selection to be made (step 7).  This isn't happening.  The selection is made, but the credit isn't removed.Hence a second selection cannot be made.  The only way to make another selection is to flip the service switch, which when put back to play, allows another selection.
  
It seems relatively simple - some circuit isn't completing, but I can't chase it down and I don't want to just start tearing into it. 

Any direction would be helpful.
Thanks,
Dave.

[jukenorman]

Hi Dave,
It's always difficult faulting finding when modifications have been made. If the latch solenoid has been removed, do you have to push both number and letter buttons together to make a selection? The credit cancel solenoid shouldn't be your problem because all it does is remove credit; disabling this solenoid is normally how free play is achieved and possibly why it's not operating. Maybe check the start relay, is it releasing after the selection has been made? Unfortunately I don't have a complete MM5 manual.

Norman.

[mrdavidj]

Thanks for the help. To your first question, yes both the letter and number buttons need to be pressed simultaneously in order to make a selection. Apparently its been like this for maybe 15 years and while a little annoying, worked just fine. The juke hasn't been on free play (they opened the cover and add credits manually with the credit button - again while annoying, it's been working fine for them until now).
I'll have a look at the start relay. I don't believe it is releasing, as I'm not hearing 'action' other than the selector/mechanism. One other item to note is I found the original 5MFD 400V capacitor was dead. I replaced it with a known good one. Looking at the schematic I see the Y/B is tied to both the latch solenoid and the R1 relay. Again I'm really novice to the MM5 and this schematic. I'm wondering if the latch solenoid isn't grounding (since it's absent), it's keeping the relay energized?

[jukenorman]

Hi Dave,
That maybe puts a different slant on things, I had been assuming free play! I presume then that you have to hold the buttons down until the search unit has completed? In that case it should operate pretty much as described in the manual - the latch solenoid is operated by the latch relay (which also operates the credit cancel solenoid). The latch relay enagaging the latch solenoid being all that's missing.

It's probably the latch relay that's failing to de-energise, that's done by a contact of the sprag relay.  The latch relay de-energising is what operates the credit cancel solenoid.

The start relay is operated by the pushbuttons. If you were to release the pushbuttons before the selection has been made, the start relay should drop out and stop the search motor - easy check to make.

Norman.

[mrdavidj]

sorry for the huge delay in follow up. This was something that didn't get actioned until today. So answering your question, yes both the letter and number need to be held in order to make the selection (has operated like this for years). Other than a little inconvenient, it works.
So the sprag relay is staying energized after the selection completes (and after the record playing completes). It will not de-energize unless the machine is cycled on/off, or the service switch is moved from on to off. Your saying this is likely the latch relay failing to de-energize. Any ideas how to troubleshoot this? It seems like it's an electrically held relay, which I don't see where it's being stuck on.

[jukenorman]

Hi Dave,
Back to my previous reply (although some progress) - the start relay is operated by the pushbuttons. If you were to release the pushbuttons before the selection has been made, the start relay should drop out and stop the search motor - easy check to make.

If that's not happening, either the start relay is faulty or more likely, there is an issue on the pushbutton switches that is holding the start relay energised when the buttons are released. The start relay releasing is what drops out the sprag relay etc..

Norman.

[mrdavidj]

Thanks Norman. If I understand you correctly, if the pushbuttons are released prior to the selection made, the start relay should drop (the selector stops spinning). If this is what is meant, then yes it does drop out. If the pushbuttons are held, the selector spins until the selection is made, the mechanism goes through the motions, the record plays and then later returns as it should. However the sprag relay remains energized, so no further selection can be input (unless the service switch is cycled on/off/on). With the switch cycling, the sprag relay denergizes (visual and audible), which then resets the start relay (visual and audible).
Dave.

[jukenorman]

Hi Dave,
That's strange but leave it with me! My MM5 manual isn't complete - but the sprag relay should drop out when the buttons release. Did you happen to notice that although the sprag relay remained energised, whether the start relay dropped out when you released the buttons - yes you did notice, I have re-read your post! The buttons hold in the start relay, it should de-energise!

Norman.

[mrdavidj]

agreed, which is why I'm not sure what's going on.

[jukenorman]

It's a contact of the search unit relay (R2) that drops out the sprag relay S2. The buttons being released should de-energise both the search unit relay and the start relay (R5) by cutting the 30V DC.

Norman.

[mrdavidj]

thank you sir, I will continue to investigate....