Sequencer question

[Lincoln]

I'm working on a STD4. One set of the chase lights are not working. Every 5th one is out. I swapped a different sequencer into this machine and all of the flights work. What part in the sequencer is the likely culprit?

Thanks
Lincoln

[Ron Rich]

Hi Lincoln,
Anything from a transistor to a resistor, to an open plug---If, by chance either one of those sequencers still has a diode with a BROWN band on it--change it-- they have a bad habit of shorting out--in ANY situation ! Ron Rich

[tonyj]

Good schematic and write up of the circuit from the late Tony Miller here:
www.west.net/~jay/fmillera/fmillera/std_%27chaser%27_lights.htm

Using a voltmeter and the schematic, should be easy to track down where the failure lies. Personally, I'd start by looking at the base of the driver transistor (Q1 through Q5) for the string that's out to narrow down if the failure is in the driver circuitry or in the sequencer circuitry and go from there.