And while car ignition systems are no longer easily adjustable, mower engines and leaf blower, and string trimmer engines still can be tweeked a bit. So the timing lights can still be useful.

How? Being there is no "timing mark" to see and the coil position is what determines the spark timing on that type engine and isn't usually moveable how does the 'tweek' work?

 

On many engines it is possible to vary the timing by adjusting the breaker points gap. Usually there is a bit of adjustment available to compensate for hardware variations. Not on every engine, but on many of them. These are not intentionally provided adjustments, but they are often available ones.

 

I can't remember the last vehicle I owned that had points ignition system.
The DIS method has been around since the 80's at least.
Max.

 

On many engines it is possible to vary the timing by adjusting the breaker points gap. Usually there is a bit of adjustment available to compensate for hardware variations. Not on every engine, but on many of them. These are not intentionally provided adjustments, but they are often available ones.

What was the last lawn mower, string trimmer, chain saw or what ever you worked on??? They haven't had points since like Max said the 80's.

 

What was the last lawn mower, string trimmer, chain saw or what ever you worked on??? They haven't had points since like Max said the 80's.

I do tend to keep my toys longer than most folks because I am able to repair them. And I seldom need to purchase repair parts, because I fix things rather than replace them.

 

I have schematics for 4 Sears timing lights, model 244.21172, 244.2115, 244.2138 if interested. Two from Sears, the others I reverse engineered. They use either 3 or 5 wire charging transformers, are inductive or not, and the pair of diodes downstream of the charging transformer either point to the Xenon tube or away from it. My question is one model uses the Signalite V139R1.9 neon tube as a voltage regulator for 139 VDC. No longer available. Can a typical neon bulb work as one finds in control switches or pilot lights? I use a timing light on a 1974 Honda motorcycle and 1978 VW Rabbit, both with points/capacitor, they run fine and can be easily maintained.

 

I have schematics for 4 Sears timing lights, model 244.21172, 244.2115, 244.2138 if interested. Two from Sears, the others I reverse engineered. They use either 3 or 5 wire charging transformers, are inductive or not, and the pair of diodes downstream of the charging transformer either point to the Xenon tube or away from it. My question is one model uses the Signalite V139R1.9 neon tube as a voltage regulator for 139 VDC. No longer available. Can a typical neon bulb work as one finds in control switches or pilot lights? I use a timing light on a 1974 Honda motorcycle and 1978 VW Rabbit, both with points/capacitor, they run fine and can be easily maintained.

A standard NE2 bulb fires around 60 volts, so you will need to put two of them in series, which should be close enough for that sort of circuit. A neon bulb with a base probably includes a series resistor and will not regulate very well.

 

Thanks for the simple workaround. I had assumed to remove the resistor but seek confirmation. Again, why is such NE-2 resistor inserted for operation, normally for use at 120 VAC, 60Hz? The Signalite inside the Sears model 244.2138 is all mirrored over inside and I have not confirmed it works. Its two rods are not shorted together. I don't know if it is supposed to glow when the timing light trigger is depressed. I've not taken any insitu readings, yet.

 

Thanks for the simple workaround. I had assumed to remove the resistor but seek confirmation. Again, why is such NE-2 resistor inserted for operation, normally for use at 120 VAC, 60Hz? The Signalite inside the Sears model 244.2138 is all mirrored over inside and I have not confirmed it works. Its two rods are not shorted together. I don't know if it is supposed to glow when the timing light trigger is depressed. I've not taken any insitu readings, yet.

The explanation for the series resistor is that it MUST be provided to limit the current to prevent the device from being destroyed. A gas discharge device has a specific voltage drop, and a negative resistance above the breakdown voltage. So after the gas inside starts conducting the current is not limited by the internal resistance. That is why they work as regulators, which is because as the voltage tries to increase, the current rises instead. So a series resistor is added to limit the power dissipated in the conducting gas.
When a neon device is used as a voltage regulator a resistor is provided to allow enough current to flow so that the voltage remains constant, similar to a Zener diode.

 

MisterBill2: Thanks for the explanation, that the resistor limits the current through the Xenon device because once it passes current, it is a lot and the power supply must be restrained.

I got the Sears 244.2139 working. At first it was dead, 12 VDC or no volts anywhere. I touched the base of Q1 with an analog VM and then it started singing and the Signalite glowed and when used on the car, worked. 650 VDC on the charging transformer output capacitor. Couldn't find any poor solder joints so wiped R1 up and down that feeds the base and left it at that. Thanks for everyone's help.

 

MisterBill2: Thanks for the explanation, that the resistor limits the current through the Xenon device because once it passes current, it is a lot and the power supply must be restrained.

I got the Sears 244.2139 working. At first it was dead, 12 VDC or no volts anywhere. I touched the base of Q1 with an analog VM and then it started singing and the Signalite glowed and when used on the car, worked. 650 VDC on the charging transformer output capacitor. Couldn't find any poor solder joints so wiped R1 up and down that feeds the base and left it at that. Thanks for everyone's help.

There might be an intermittent connection in that resistor that you touched. If the light stops working again, let everything discharge and then, with the power disconnected, check the resistance of that resistor without pressing on the leads close to it. Some composition resistors get loose inside and have a poor connection. Hard to find because it often fixes itself for a while.

 

The first things I touched was everything except the Q1 base and the R1 wiper. Saw 0 and 12 VDC, nothing else. I had been on the Q1 collector, voltage 12 VDC, apparently not turned on. I became further curious. I touched the Q1 base to see if it was turning on and that got it full up and running. Didn't need to look at the collector again, didn't need to. I looked for poor solder connections, didn't see any. A minute later I considered the R1 wiper while powered down. I swept it up and down just to clean it and it turned so freely I wondered if it was even making internal contact. I don't know. I may take its resistance reading so if it fails again, I'll place with a non-adjustable resistor.

 

I have a Sears Inductive timing light as well. Just reverse engineered it as I thought it stopped working but then it hadn't. One component in it I couldn't identify. Let me know if you want it or if it should be displayed.

Do you have one for the 282134 model?

 

@amcarter1990
Welcome to AAC!
You are posting in a 3-year old thread. Better to start your own if you expect a reply.