Diy Strobe for measuring turntable speed accuracy.

[Steerpike_jhb]

a 45rpm strobe disc that is accurate under 50Hz lighting. The closest you can get is 45.112rpm

Fascinating!! So would you offset the crystal to get it accurate??

I have recently learned that most discs are actually cut at 45.11, and not 45.00 - because the cutting lathes were mostly driven from synchronous motors.
So the 'error' in the strobe disc turns out to not be an error at all, because you dont want 45.00.

Quartz turntables that do exactly 45.00 are apparently wrong.

will the disks work under a compact florescent light?
and are the little dots supposed look like they aren't moving, or should they be blurry?

Generally CFL lamps don't work - they don't flash at mains frequency, they have their own oscillators inside.
The blurriness of the dots depends on the 'quality' of the strobe waveform. My DIY version gives significantly less blurry dots than a mains-powered neon or LED lamp, because the current pulse to my LED is very short.

So how do i tell if my turntable is going at the right speed?

The strobe ring appears to stand still, as if it were not rotating at all.

[rito25]

So what kind of light source should I use?

[Damien Taylor]

Either mains incandescent or the specially made strobe unit.

[denti alligator]

I'm not able to create my own strobe. What's a good source for a cheap fluorescent or strobe light that will do the job?

[Conrad Hoffman]

LED night lights don't have much filtering and will flicker at line frequency. The contrast of the pattern will be low, but they're quite usable if the room lights are low. IMO, you're way better off with a simple neon bulb and resistor. A neon bulb flashes on both positive and negative cycles, so you get a 120 Hz (USA) flash- what most strobe disks are optimized for, and what gives you the best contrast.

My alignment template program also prints nice strobe disks-
http://www.conradhoffman.com/chsw.htm

Best,
Conrad

[Plattenbau]

Hello everybody,

the thread is kinda old, but maybe somebody could still help me out there with my problem.
I'am not a total newbie in electronics expecially when it comes to turntables. I own a record shop in germany and do repairs and refurbishes on turntables every now and then, with no major problems so far. However I can only build/repair basic electronic stuff since I don't have professional equippment and/or professional skills.
However... this little circuit is killing me, and before I waste another set of ICs I thought I try to ask the community first.

I etched six PCBs which come out very nice and clean and thought to build a prototype first - leaving the trimmer capacitator c1 out and using 22pf capacitators for c2,c3. I used just one LED, bridging the other 2 LED slots. In my second prototype I also used a bridge instead of a switch, since I don't had any left. I had to use substitutes for the ICs, since I haven't found the exact ones in germany. I asked in a lokal electronics shop, an they said it' fine (IC1 = hcf4060be, IC2 = hef4013bp). I made no further alterations than these to the circuit.
When I connect a batterie and pushing (or on the second pcd only connecting the batterie) the switch the light doesn't turn on, but the batterie gets pretty warm/hot... and so does IC2...

So if somebody is able to help me with that, I would appreciate it!

thanks a lot!

Dennis / Plattenbau Aachen

[Steerpike_jhb]

There is an error on my PCB overlay diagram - I think it was mentioned in this thread a while back, the LED flat side should face away from the ICs.
The longer pin of the LED should be closest to (snip) the ICs.

This should not cause the serious overheating you describe though.

Try your circuit without the LEDs inserted, see if IC2 still gets hot.

The substitute chips you used are fine - no problem tere, BUT be aware that these chips are damagd by static electricity and handling in dry weather. They should have been sold to you in protective conductive tubes or the special black or pink bags.

[Plattenbau]

Tried that - same thing!

The dealer is reliable. I ordered the first set of ICs online - I have the same problem with them. I'll pick up my camera from work today and post a picture - maybe that helps. If you have another idea till then, just let me know!

many thanks,
Dennis

[MelodyMaster]

Anyone tried viewing the strobe disc by the light of a television screen (conventional CRT type). That would be a very accurate 60Hz reference - IF it provides enough light. (0r 50Hz in europe/south africa)
(must be a real broadcast - although a DVD player ought to give a very good refence too).

That would be 59.97 Hertz, which is virtually the maximum allowed slowdown during peak power consumption periods in Canada. (The system runs fast overnight to catch up, average frequency over the full day must be exactly 60 Hz to several decimal places.)

Necromancy, heheh, I didn't see that it was the first page. That's valid info though...

[Steerpike_jhb]

That would be 59.97 Hertz, which is virtually the maximum allowed slowdown during peak power consumption periods in Canada. (The system runs fast overnight to catch up, average frequency over the full day must be exactly 60 Hz to several decimal places.)

D'OH! I forgot they changed the TV frame rate for colour, oops I mean 'color'. 59.94 Hz I believe. Still for PAL and SECAM countries, it is exactly 50.000Hz

I measured quite large instantaneous changes in mains frequency, which would have an impact on synchronous turntables, although would not show up at all in a daily average.
Such ac-mains frequency fluctuations would show up on a strobe disc illuminated by a tv set; even if the tv frequency is "off" by 0.1%, it remains rock-steady.

[Steerpike_jhb]

TIf you have another idea till then, just let me know!

I assume you have checked the board for shorted pins by solder blobs.

Is your transistor a BC327, or a substitute ?

[Steerpike_jhb]

Note to JaS:

I have just sent you - by normal e-mail to admin - the .pdf of the diy strobe project WITH THE LED ORIENTATION ERROR fixed.

This error was mentioned in the forum posts some time ago, but for new people who download the PDF and don't read the old posts, it could be a problem.

The error: On the component overlay diagram, the LED outlines were shown with their flat sides (cathodes) facing down towards the cmos chips. The LEDs should be installed with their flat sides facing up towards the transistor.

[MelodyMaster]

That would be 59.97 Hertz, which is virtually the maximum allowed slowdown during peak power consumption periods in Canada. (The system runs fast overnight to catch up, average frequency over the full day must be exactly 60 Hz to several decimal places.)

D'OH! I forgot they changed the TV frame rate for colour, oops I mean 'color'. 59.94 Hz I believe. Still for PAL and SECAM countries, it is exactly 50.000Hz

I measured quite large instantaneous changes in mains frequency, which would have an impact on synchronous turntables, although would not show up at all in a daily average.
Such ac-mains frequency fluctuations would show up on a strobe disc illuminated by a tv set; even if the tv frequency is "off" by 0.1%, it remains rock-steady.

Sorry, I meant 59.94, I was thinking field rate which is 29.97. I'm a TV tech yet I always make that mistake.. But no, a TV can't be used for strobe reference here.

[Plattenbau]

TIf you have another idea till then, just let me know!

I assume you have checked the board for shorted pins by solder blobs.

Is your transistor a BC327, or a substitute ?

yeah - did that... sadfully without a result! for a transistor I used the "original" bc327.

Cheers,

Dennis