Inigo wrote:Usually these modern hmv motors have three features to help adjusting it in a fixed position.
The tt spindle has a notch where the set screw of the spindle gear must be positioned.
The governor axis also has a notch where the set screw of the governor fixed collar set screw must be positioned.
Finally, one of the governor bushings, the one which resists the pushing of the spindle gear, has a channel in the middle, where the set screw must be placed. The opposite bushing is plain, so this is the one with which you play to adjust a minimum gap for the governor.
All these things are designed with the aim to install the governor and the spindle gear in their correct positions.
With these parts correctly installed in their fixed positions, there should not be any problem running the motor correctly...
Good evening Inigo, thank you for the detailed explanation. I'm away and cannot look at the motor right now but I'll come back to it at soonest. I suppose I should dismantle the governor shaft and bushing to see these notch and channel, am I right?
following your advice I double checked the position of the governor shaft. I did not dismantle completely the mechanism, but I noticed that on the left bearing there's something like a "reference line": if my understanding is correct, the bearing should be moved until the reference line almost touch the spacer between the two motor motor plates, therefore ensuring that the governor shaft is properly placed. I proceeded like this and now the motor appears to pick up speed and spin regularly. I re-assembled the motor on the board and also tried to "fine tune" the turntable speed so to have it spinning at 78 rpm when the speed regulator lever is in the middle position of the index plate. It was a hit and miss process moving by minimal increment the speed regulator assembly along its slotted holes, tightening the screw, checking the speed, and then all over again until I reached the position where the nominal 78 RPM corresponded (more or less
) to the middle position of the lever. That's all!
By the way: somewhere in the web I found a printable image to arrange a stroboscopic disc for european 50 Hz current and so I glued it to a worn-out record only to realize that I have not a single spare incandescent bulb light to use with it after having switched to led and other low consumption lights! Everywhere I read that the strobe discs should be used only with incandescent bulb light, but since it was not feasible I turned to a quality led torch I use for my daily job: to my surprise the stroboscopic image appeared neat and sharp when the motor speed should have reached 78 RPM!
Not totally convinced I picked up a record whose tune I know the pitch of, and I played along it at the piano: even with some notes being minimally out of tune, I could almost follow the melody at the keyboard with more than acceptable results, hence I concluded that the gramophone plays at a correct speed. So far, so good...
Thanks for all your hints!