[Wayner]

I think there is some confusion on this topic, mainly for some newbies but maybe we should have a short discussion on the subject and you guys can comment if you want.

The strobe disc has been designed to help identify speed issues with turntables. They are specific to speed (33 1/3, 45, etc) and to cycle of electricity.

The first thing about a strobe disc is having the right light source. An incandescent lamp will not work for this application as it's light source is continuous. Because it's a filament, it glows regardless of the cycle. The filament is seeing the 60 cycle hit, but reacts way too slow to get a real stroboscopic effect.

The fluorescent lamp is the correct light source for this task. This lamp reacts quickly to the cycle change in the electricity and the lamp actually goes on and off 60 times per second. Kind of like watching a movie. It's really made of individual still frames, but played fast enough, looks like actual motion. Same with the strobe disc.

The disc is designed with speed (RPM) and cycle (60hz) in mind, 50 hz in other nations.

The strobe lines are in a specific place and degree so that as the table is spinning and the lamp is busy flickering at its 60 cycle on and off rate, the lines of the disc are in the same position as the light "comes on".

If you view just one one spot of the disc when it's running under fluorescent lights, the lines turn into a gray colored band. Inside the band are darker appearing lines that appear to stand still. If you have a DD turntable with speed control, you can demonstrate this easily by adjusting the speed up and down, observing the line behavior drifting to the right when the speed is slow and drifting to the left when the speed is too fast.

Is this a good explination or can you guys add to it?

Wayner

[Wayner]

Today, I've learned that all fluorescent lamps are not the same. Sonny got one of my strobe discs and was having a terrible time seeing the lines standing still. So I went down to our local Menards and bought a small fluorescent lamp. The lamp was a F6T5, 6 watts, .625 diameter. When I got home, this sucker would hardley show the lines.

New theory is that the small electonically ballasted fluorescent lamps have knocked down the 60 cycle effect (that I'm sure bothers everyone) and thus turned these style lamps into useless strobe watching lamps ( I'd like to see the waveform on an Oscilliscope). I now have 3 lamps that produce effects from non-detectable to wow, look at the lines. So anyone interested in getting a strobe disc, let me know and I'll get you one. As far as the lamp source, well, I have a magnetically ballasted PL-13 twin tube lamp that works great. For Sonny, I found a PL-13 trouble lite from Prime Wire and Cable (www.primewirecable.com) and it works the best of any of these. Not only that, when it's not the light source for my strobe disc, it has uses as a trouble light.

****************************************************

Here is some more interesting math to a stobe disc's line pattern. The guys that make and sell these will hate me, but tuff. The lines on a stobe disc each represent 1/2 cycle. 2 lines then equal a cycle. Isn't it funny that the angularity between the 2 lines for the 33 1/3 RPM @ 60Hz is exactly 3.3333333333 degrees?

Isn't it also funny how the 45 RPM lines (again, each line is 1/2 cycle) and the angular measurement between 2 adjacent lines is 4.500000 degrees.

I'm always amazed at the math. How does this shit do it?

Anyway, there is more useless information from:

Wayner

[twitch54]

My flourescent trouble light works perfect for checking caibration with VPI and SDS unit.

[analognut]

I have an architect's swing-arm desk lamp on my computer desk that I can just swing over to the TT when I need to check the speed. This lamp has a screw-in bulb and also an FCL 22w 6400K round 8" flourescent lamp which strobes exceptionally well. The screw-in bulb I use is one of the new-fangled flourescents that have the spiral shape and the ballast in the base, and it don't strobe worth a darn.