Automotive Timing light

[Speakrdude]

Anyone know how to troubleshoot a timing light? This is not a very expensive light, around $70.00 on Amazon but it was my favorite with digital RPM and Advance function. It is around 2 or 3 years old. I hate to just throw it away!

The problem is the strobe intermittenly worked and now, longer works at all. The rest of the unit functions fine. I have check all the obvious items, solder joints, etc, but not sure how to troubshoot the rest of the strobe firing circuit or the bulb itself.

Thanks,
Jim.

 

[Speakrdude]

Oh by-the-way, Its an Innova Equis 3568+.

 

[TBennettcc]

You feel comfortable opening it up? (I would assume yes, since you said you checked the solder joints...)

Can you get any voltage readings from where the bulb plugs in to the unit? Any chance you can get voltage readings from different parts of the circuit? I'm not sure what all the 'obvious items' are. Is there any way you could make a schematic of the board, or post very high quality, crisp, clear, clean photos of both the front and back of the circuit board with as much lettering exposed as possible?

 

[daddles]

Be careful around the flash tube -- it's likely that the circuit pulses the tube with pulses that are a few hundred volts (I'd guess between 200 and 400 volts) to flash the tube. Plus, there might be a good-sized capacitor in there that might be charged up still after you've taken the thing apart. Usually, there's a "bleeder" resistor that slowly discharges the capacitor, but it's not guaranteed.

 

[Speakrdude]

Yes, I am good with basic electronics repair on the board level. (I do not attempt to repair surface mount because I do not own the proper equipment)
I can take nice, clean, crisp pics and post them here, no problem. I can take measurements anywhere but not sure how to make it fire the strobe without being connected to an engine plug wire.
Yes I know about the couple hundred volts within the (large cap) located very close to the strobe.
By checking the basics, (from my high school shop class teacher) "Check the stupid things first!" The power in, the condition of the solder joints, burn marks, fuses, power supply voltages, etc. Of course, back then, we were repairing TV's and testing tubes when you weren't busy (anyone? anyone?)
Jim

 

[(*steve*)]

Problems with things like this fall into one of 3 categories.

1) failure of lamp
2) failure to store energy for the discharge
3) failure to trigger the discharge

The second is easiest to test. See if there is a high voltage appearing across the capacitor near the flash tube.

If the flash is not triggering (and this device possibly just takes the high voltage direct from the spark plug lead) then you will see a constant voltage on the cap. If it is triggering, the voltage will drop then rise again as the capacitor is recharged. In this case the unit is designed to flash very rapidly, so you will probably not be able to see this on a multimeter, although the average voltage should fall.

If it is triggering, then unless the storage capacitor has gone very low in capacitance, you may have a broken flash tube.

 

[daddles]

I'll assume the thing has an inductive pickup, so this is another thing that can go wrong. Dirt can plug the thing up so that it doesn't close properly, creating a large magnetic resistance. Then the light would not fire because it wouldn't receive a trigger signal.

It's going to be a bit of a challenge to troubleshoot this without a scope and a schematic. The best approach is to take some good pictures of the circuitry. Two hints: get outside in some indirect light (an overcast day is perfect or a northern exposure out of the sun) and make sure things are well lit and b) use up the whole frame. Sorry if those are obvious, but the vast number of people out there don't realize how easy it is to take decent pictures (excluding composition, the main thing is good lighting).

 

[Speakrdude]

I figured since the digital tachometer portion of the gun was working, the pickup must be ok, seeing how that is where it gets its info too,correct?
I will take your advise on the pictures. God knows we have plenty of sunshine here right now.