Free turntable speed check strobe

I use the following method to check for speed accuracy. I can't say whether it's more accurate than any other method, but it is free and only requires a stop watch and some time.

Place a line on your turntable platter and place another line on the turntable's top surface. The lines are used to count platter rotation. Start the platter in motion and using the stop watch observe the number of rotations the platter completes. In 3 minutes you should observe exactly 100 revolutions; in 6 minutes 200 and so forth. Six minutes is probably the minimum time needed for an accurate measurement.

This method can also be used with a record playing.

The original M&K Realtime LP's have a strobe disk printed inside the label area. I have checked this with the KAB and they are the same.

So for those fortunate enough to own any of those great M&K direct to disk's, they may be measured while playing as well.

How do I use this to check the speed? Do I just place it on the platter, spin the platter, and use a stop watch and count the turns like what Onhwy61 suggested?

Gundam91. If your question concerns the free strobe disc, holding a neon lamp near the rotating lines while playing it at the proper speed will make the lines appear to stand perfectly still.

If the lines run backward you are too slow. If they run forward the table is running too fast.

No download needed for the stopwatch gig. Just make a mark on the platter with masking tape and start counting. Much more patience required than shining the neon light and observing whether the lines appear motionless.

I just measured the accuracy of the downloadable disc to see how it checked out. I first verified the digital speed read out of this table by using the KAB Electro Acoustics strobe disc. I could leave the table in the preset 33.33 rpm mode and it did not vary from being perfectly strobed and showing the correct speed. As such, the KAB strobe disc and the internal clock of the TT show perfect sync. When i put on the downloaded strobe disc and used the KAB strobe light, i had to vary speed ever so slightly to get it to stand still. When all was said and done, the digital read-out on the TT registered 33.20 rpm.

While this is pretty close ( off by .13 revolutions per minute ), i don't know if it was caused by printer error or is a design error on the disc itself. As we all know, most consumer grade printers are NOT "precision" instruments. While the one that i'm using used to be Hewlett Packard's top of the line model, i've seen it do plenty of strange things. It would be nice if someone else could post their findings and state what they used as points of reference. Sean
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PS... In case you're wondering, the table in question is a ReVox B-791.