MM1 Search motor spins continuously - wiper not find hot??

[AlanMacD]

Hello,
After weeks of reading forums, watching videos, cleaning contacts, using an eraser to clean pcb, checking for 30vdc, I am at a loss for why my search motor just spins continuously. Here is what happens...

-turn unit on
-select V-8
-buttons engage and stay pressed in
-search motor starts and a clicking of the sprag 1 S1and contacts can be seen and heard
-search motor continues to spin forever, never pushing a pin.

I am assuming two things could be the issue
- The wiper arms aren't finding the 'hot' side of the selection circuit
or
- no current is making it from the pcb to the selector coils to fire a pin

I have adjusted the wiper arms and blade contact force, adjusted the sprag relay per the manual, check continuity of all the pushbuttons, sprayed in there with contact cleaner and pushed all the buttons numerous times. 

If I manually move the contacts below the S2 briefly, the search motor stops, finds a record, puts in on the turntable and plays. 

Any help or suggestions? I am going mad over here.

In miami florida if that helps. 

[jukenorman]

When you say "a clicking of the sprag 1 S1 and contacts can be seen and heard", do you mean that it's not staying energised? Did you change the 1,000uF capacitor in the power supply? Maybe the DC supply isn't capable of energising it fully in the available time frame if the capacitor is poorly?

Norman.

[AlanMacD]

Thank you JukeNorman for the reply.

I made a video of the S1 contacts activating but the search motor continues to spin without activating the pin.

I will try to add it here.



I will check the power supply, not familiar with that area yet so I will go through the manual and locate it.

Thank you!!!

[jukenorman]

Hi Alan,
Yes that's what I thought you meant! The search motor runs until the number is found, S1 should then energise locking the number. The search is then transferred to the the letter but because S1 is not locking, S2 will never operate which leaves you stuck in no man's land! It could well be the capacitor but if it's not, it's contacts or connectors - and I have noted that you have been working on these.

Norman.

[AlanMacD]

In the manual, there is a junction box wiring diagram. If i trace the path from the on/off switch, it runs through a transformer, then to a capacitor that is in between the transformer, mate-n-lock, rectifier. I know its probably hard to follow that without an image but is that the general location of the capacitor i am looking for?

[jukenorman]

Yes, junction box is how it's referred to - it's the external can in the picture below. Capacitors are much smaller these days than they were sixty years ago so you can probably leave the original in place, snip the positive connection and connect an axial electrolytic inside the junction box.


Norman.

[AlanMacD]

yep! got it. My unit is rotated 90 degrees from that picture. Yes, the capacitor can is big and in a cardboard tube. You are right, the replacement capacitors are much smaller today. Ill give it a go once I get a capacitor.

In the meantime, which specific switch or relay should i double check to be sure its not a connection? Im assuming its upstream of S1 so it would be keyboard pushbutton related? How could I check if 30v is coming from the number pushbutton down to the pcb?

[jukenorman]

Because S1 is making an effort at energising, it not going to be an open circuit that's the problem so you will have difficulty effectively tracing it with a digital meter. You could check the DC voltage at the fuse on the junction box with no load and then see what happens there when a selection is made - but as I said, difficult with a digital meter. But if it looks as if it's dropping, that would probably point to the capacitor. As a first pass, what DC voltage are you getting with no load ie jukebox doing nothing.

Norman.

[AlanMacD]

Thanks again. Thats what I figured that since s1 is energizing, probably not an open circuit, but Ive read so many forums and youtube videos where they were like 'wow! I cleaned the keyboard, or pinched a terminal or cleaned the r1 and r5 and bam! it all works" So I was hoping for one of those fixes, haha.

I pulled the fuse, put the positive probe in there and grounded the negative on screw to the frame and saw 9-11 volts on my digital multimeter. Is that the best way to do it? Is there a good ground like a bus bar or something? I didn't put a load on it as I was worried I was doing something wrong or possible stupid. Any thoughts?

[jukenorman]

9-11 volts doesn't look like a valid reading, S1 wouldn't be budging at that voltage. Having removed the fuse, you could be reading the "wrong" side and getting a spurious value. The metal chassis should provide a decent ground.

Norman

[AlanMacD]

Thanks. how to read the voltage with the fuse in place? when i take the black bayonet style cap the fuse pops out. any suggestions?

[jukenorman]

If you look at the 6 pin plug/socket in the diagram, pin 1 is 30VDC and it most likely has a red wire. The other pins on the corners (3, 4, & 6) are all ground. So if you can't identify a red wire, measure the diagonals - one diagonal should be 0V (two grounds) and the other should be 30VDC, which with no load will likely be a bit higher.

Norman.

[AlanMacD]

I got 30VDC from the red. So, I have a capacitor arriving in the next couple days and will wire that in when it gets here.

Again, Thank you so much for your help and guidance. These are awesome machines and I am so interested in learning more about my mm1. I am 41 years old, and it was in my home for a few years before I was born, so I have a lot of memories playing this as a young kid. I am so eager to get it going again. My parents now live with me and I would love to get it playing a tune soon.

I will check back in here once the capacitor switch is made.

[jukenorman]

Hopefully the capacitor will do the trick - but if it doesn't, it will have been eliminated as an issue. We'll get there!

Norman.

[AlanMacD]

Well, I opened up the power supply and guess what I saw?!?! A new modern capacitor soldered into the circuit like you had suggested. In a few hours I’ll get back to it and cut it out, test it and maybe put in the new one anyways.

I’ll keep you posted