ssuel wrote: Tue Nov 08, 2022 12:23 pm
I do have the PowerPro manual but I guess what puzzles me is why did the screws loosen after being set at factory. BTW I will follow manuals procedures for tensioning and balancing the belts. Just seeking insights on best way to prevent the set screws from backing out in future
There has been more than a few threads that discussed this, but basically the PowerPro motor is more prone to vibration issues than a standard induction motor for this application. I explain why (my theory) at the thread linked below and Bill gave a very good hysteresis theory as well at the 2nd link. Either way, this is a known issue. Most PowerPro owners see this as setscrews (drive hub for example) backing out and have had to put thread locker on them as a result. Most likely this is also going on for the screws you show here and you may have to consider putting thread locker on them as well.
First thing to know is that the outside Button Heads lock the inner and outer parts of the mounts together after adjustment, so if the adjustment screws do move they don't change anything. The four adjustment screws work together and interact, adjusting both tension and the up/down angle of the motor shaft. In order to increase tension, you would first unlock the outside SBHCs (4 IIRC). Then tighten the setscrews both equally, say a half turn. Then you would loosen the adjustment SBHCs by the same amount 1/2 turn to maintain the angle. Then tighten the lock SBHCs. Then balance the upper and lower bels via the eccentric bushing. Then see if you are happy with the tightness of the two belts. Make small adjustments at a time, to minimize the impact of the interaction.
Assuming you don't want to change the adjustment, just turn the setscrews in until they are in contact, snug not tight I'd say. I'm not sure how I feel about loc-tite on these. Nylon patch or Nylok would be a better choice but I don't know if either is available. This is a good place to mention that most fasteners specific to the PowerPro are metric.
More relevant: There are six counter sunk flat-head screws, three per side, that attach the motor, mounts, etc. to the headstock. You can tilt the motor to remove the belt by removing the four furthest from the belt and slightly loosening the two nearest the belt. Then tilt the motor to remove all tension and pull the belt. Follow the video advice for a work surface when you remove the remaining two screws and take the motor out. The motor is heavy, the fan cover is plastic, the wires are short. If you remove the motor this way, there is no need to adjust belts afterward unless they needed it before you started.
Just got back on my repair project and got down to pulling the control panel off. So far the 10-pin ribbon cable was loose just barely connected and not snapped together (probably explains intermittent power issue and control panel responses). Also took a couple of pics to show that the green circuit board silver mounting screws have been loosening allowing the the circuit board to vibrate —- probably responsible for the ribbon cable to not be firmly attached too.
The label was still stuck and holding . Hopefully I’ll get a chance to put it back together in next few days
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Interesting. Newer units have a glob of adhesive on those screws, now I know why. I'm not sure what the adhesive is, I had a supplier that used a thick UV-activated adhesive to attach wires to PCBs and it had a similar look. The 10-pin connector doesn't have a latch or snap like the other connectors do. Probably works well enough until the screws start backing out. Were the two screws that mount the assembly to the headstock still tight?
RF Guy
Were the two screws that mount the assembly to the headstock still tight?