Rockola 480 gripper motor issue

I have a Rockola 480 that I have been trying to bring back to life. It is almost there. I can now add credits and the correct record is chosen and played and returned. Twice. The third time I select a record, the gripper motor stops as soon as it starts to come in to grab the record from the carousel. I can finish the cycle by turning it by hand and it will play and return the record just like normal. I then can cycle the main power and it will work for another 2 records. I figured it was the motor being a little dirty so I cleaned and lubed it. It ran much faster but did the same thing. I have not tested for power during the third cycle as it was late and I had to get to work early. I plan on testing that today when i get home. Was wondering if there was somewhere else I should be looking too. Thanks for any help that you can supply. (yes I have the books)

Dan

Dan, gripper motor failure is common to all R-O models from the early 1950s till the end of vinyl.

Check the condition of the brushes and commutator.

---Be sure to check the value of the Low-DC fuse as these are often increased as the motor begins to have shorts in the armature and drawing higher current.----

Another area to check are the micro switches on the cam near the tonearm. When the motor stalls, does turning the knurled end of the armature get it to start again?

Rob-NYC

Rob,
Thanks for the reply. When I took the motor apart last night the brushes where in good shape (wasn't expecting that). I cleaned the commutator but it also looked to be in good shape (I did not run any continuity tests on it). The motor ran much better after I cleaned it. Almost scared me it ran so fast. The micro switches are in good shape and adjusted according to the manual. I can now feel the motor want to move occasionally (not all the time and never before I cleaned it) when I turn it by hand but it will not take over and run by itself. It is funny in that it works for 2 records then stops the picking up the record, but always places it back in the carousel even if I rotate the gripper by hand to play. I can then cycle the power and it works for 2 more records. I just want to rule out any power issues before I replace the motor. I will check the fuse when I get home.

Thanks Dan

Hi Dan,
I would GUESS that either your motor has a "dead spot" or you have a poor contact somewhere in the chain that supplies power to the motor--might meter the supply first ?? Ron Rich

Yeah was planning to get the meter out tonight.

PS: just was looking at the circuits for the gripper motor at lunch and noticed they are 2 different circuits to control the direction. Different than what was in my mind. I just wonder if I have a weak transistor in the forward side. Any thoughts on that? (Thinking q303?)

Thanks again Dan

Dan,
I have never seen the schematic--but I question why they would have added a "transistor" to drive a DC motor, which, for years, was direct driven ? I suppose it's possible, but "according to Hoil", it's not possible ?? Ron Rich

Ron,
I can scan the pages I am looking at if you want. It appears to me the forward motion goes through latch relay then the #2 micro switch then the q304 and q303 transistors to the gripper motor. The reverse is driven off the reverse relay through transistors q301 and 302. Makes more sense to me to just drive it off the relays though (which is why I couldn't figure out the power could run it one way and not the other). I believe they would do this to have the low voltage control the higher. Smaller wires/smaller relays cost less?????? Then again, I could be completely wrong.


Thanks, Dan

Hi Dan,
No need to scan them-just seems odd to me, as I recall many of the older models, pre- transistor daze, where they just used relays to control the 24vdc ?? Mustabeen some injineer justifying his job ?? Ron Rich

Ron,
I should have got the tester out at midnight last night. When it went to place the third record I got very low, inconsistent voltage (but there was some). The motor was trying to move but not enough juice to make it go. Pretty much narrowed it to the mech power board. Tried the 4th record and no power at all. I started to freeze the transistors with no luck. Then I bumped the latching relay and it jumped. I grabbed it and twisted it and it placed the record no problem. It was warm to the touch, but that is not all that unusual for a relay. I guess the magnet coil must be getting warm and breaking connection. This also makes sense that when I choose a record it rolls past the selection because the dynamic brake also goes through this relay. I'll source a new one and see if it works. Thanks for the help.

Dan

Hi Dan,
I'm wondering--- you say you "twisted it" ? If so, could you have forced the contacts on the relay to make better contact ? You should be able to see if the relay coil is pulling the armature every time, or not ? Ron Rich

Ron,
By twisting I mean just that. The more records I played the harder I had to twist it. I tried splaying the contacts a bit to see if they would make better contact, but no luck. Since it makes good contact when cool, I would think there should be sufficient contact when warm. I believe the coil is getting hot and breaking connection. I was going to see if local store has a better contact cleaner than what I have to see if the terminals or plug block are a little dirty. Do you know of a place to get these relays? I searched online for 3 hours last night (much to the dislike of my wife - 2 nights in a row) with no luck. I was going to see if Durfree had one used but wasn't up for that last night. 5 hours sleep isn't what it used to be.

Hi Dan,
I don't know what type relay RockOla used, on that model, but I seriously doubt the coil is opening--I have never seen that happen to a relay--I would suggest that you read above, in this section, the posts on, "How to clean contacts". It's rare, but also possible that a contact on one or more of the blades is not fixed tightly, and once "hot", it is failing to make good contact with the switch blade ? Ron Rich

Ron,
I had to get the magnifying glass out, but yes, one of the contact arms was twisted out of alignment. Cleaned the gold contacts with the credit card soaked in cleaner but did not get much off. Replaced it and played records for next hour. THANK YOU! I just have couple other minor things to take care of in the future. I think I am just going to enjoy it for a little bit. Thanks again.

Dan

Dan,
Great--glad it's fixed ! Enjoy --
Ron Rich