Flashing strobe on SP10

[TBL]

Recently The strobe light on my SP10 has started flashing/blinking and not in the normal way. It does this across all speeds. I'm guessing that either the strobe light itself is faulty or more worryingly the speed itself is not correct.

Anybody come across this before?

[lurcher]

Mine did that to. It would go through weeks without lighting at all. The strobe neon supply voltage was correct, so I assumed it was the neon(s) getting old. I eventually replace them with blue leds (its not a direct replacement, can't remember exactly what I changed, but if I looked at the diag again it would probably come back to me).

[Reid Malenfant]

Neons do age & then flicker randomly before giving up altogether :rolleyes:

You could probably get away with an LED & a high value series resistor & a diode of at least 400V PIV rating to prevent reverse voltages on the LED. A 100K 2W resistor should do the job though in theory a 1W resistor should be ok. This could replace the neon which is simply directly accross the mains with a current limiting resistor (usually 270K ohm).

[lurcher]

Neons do age & then flicker randomly before giving up altogether :rolleyes:

You could probably get away with an LED & a high value series resistor & a diode of at least 400V PIV rating to prevent reverse voltages on the LED. A 100K 2W resistor should do the job though in theory a 1W resistor should be ok. This could replace the neon which is simply directly accross the mains with a current limiting resistor (usually 270K ohm).

I am guessing you are talking about a mains driven neon, this isn't. There is a 100v (I think, maybe more) line from the power supply, the neons are driven from the clock divider on the logic board.

[Gerry]

I am guessing you are talking about a mains driven neon, this isn't. There is a 100v (I think, maybe more) line from the power supply, the neons are driven from the clock divider on the logic board.

Nick
I think it is 180v for the strobe.

Don't do as some, and use the 5v line which is also supplied to the TT. This (LED) introduces a lot of noise into the circuit.

[lurcher]

I originally though I had used the motor supply, but I didn't, I used the 5v rail. Not sure how it can induce any more noise on the 5v rails than the assorted pulse stretchers on the logic board. Its not as if the LED switching is uncorrelated with the rest of the board logic operation, so I would question the description of it as noise. All the logic on my board is now modern CMOS anyway, so the PSRR and switching loads on the supply will be far less than it was originally. All the bipass caps have been replaced as well.

I would think keeping it away from the xtal oscillator would be a good thing to do. Which makes me wonder, has anyone tried using a low jitter clock source with a sp10, the original clock circuit is a little crude, and the entire thing hangs from it.

[lurcher]

Just checked, its 140v

[Gerry]

Just checked, its 140v

Nick, sorry I was going from memory.:doh:

Richard at Vantage is the one who suggested the noise increase from the 5v circuit. I like you didn't think it would ad any...he was fairly adamant that it would and suggested working off the 140v line with 2 or 3 led (I can't remember), as this was purely for the strobe. I can't remember the exact details but will check with him.

I never got around to getting my strobe working again.