The Incredible Technics SP-10 Thread

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#2,983
After reading more of JP's posts in the mk3 thread, I shot another video of the sync position trace wile stepping through the speeds.

Unless I'm misunderstanding something, I think the offset voltage is set correctly: the trace looks stable and recovers quickly without excess oscillation when changing speed or applying a load to the platter.

Again, thanks for the help and patience.

https://drive.google.com/file/d/1GqJKdTVeaofOqBrtWgkLy23YF2JxZ_jh/view?usp=sharing
 
#2,985
JP said:
Seems fine. If it starts vibrating after being warmed up, back it off a hair - a little overshoot is fine. Is your vibration gone now? Other cals able to be set?
Click to expand...
When I mentioned a vibration, I may be over critical. I'm comparing it to my VPI TNT Jr. where the motor is in a seperate massive chassis and connects to the massive platter via a belt. If you touch the plinth on it, you feel nothing. If I touch the motor pod on the VPI, you do feel a vibration, similar to the SP-10. Maybe I just need a 100 lb cast iron plinth.😀

All other cals are fine except RS current setting which I can't get below 0.162 V.

Checking w&f with the Feickert Adjust+ software & test record, I get .08% while my Denon which is closed loop gets .03%. I've attached plots of each if anyone is interested. Strangely, they're both a 33.41, possibly a software glitch.

Thanks
Technics SP-10-Speed.jpg
Denon DP-80Speed.jpg
 
#2,987
JP said:
Something’s wrong - shouldn’t feel a hint of vibration. How much is the FG signal moving around?
Click to expand...
FG, frequency generator, or what the service manual calls "liquid crystal oscillation"? That's rock solid when viewing with my scope - see attached of wave form. Could this be mechanical? I do have a new thrust pad that I haven't installed yet.
 

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  • FrequencyGenSignal.jpg
    FrequencyGenSignal.jpg
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#2,989
JP said:
FG is the frequency generator from the motor. Control board CN205 (FG Out). Mess with the platter while watching it so you get a sense of it.
Click to expand...
The manual shows FG signal in, IC201 pin 16? When I attach my scope to that I see a clean sine wave but it's amplitude undulates (grows and shrinks) at what looks like a constant frequency. It's more noitcable at 45 & 78. The vibration I feel seems to pulse at that same frequency but the frequency of the vibration doesn't change.

Sorry if I'm missing something.

Thanks
 
#2,997
#2,999
JP said:
What’s your time base? You’re looking for a 5.55Hz signal
Click to expand...
Ah, my ignorance is showing. Is it easier to view low frequency signals with a digital scope? This is the best I could get with my Tektronix 2235 unless I'm missing something. My multimeter displayed 5.6 Hz and other values as it tried to figure it out but 5.6 kept re-appearing.

Scope was set at 50 ms/div. The signal appears somewhere arount 5 Hz.
https://drive.google.com/file/d/1oU16sx2hqfKqV17ne6GAMlDj3q_538Yn/view?usp=sharing
 
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