The circuit isn't totally unknown, it seems to be a 555 timer with two resistors (one wheel type potentiometer and a single-value (47kΩ±5%)) and a capacitor to make up the RC timing circuit (I say seems because the surface mounted chip has a big black glob of something on it and it looks factory installed, so to speak).
There is no identification as to the manufacturer (I wouldn't want to claim it either, honestly) anywhere on the case, only an FCC tag stating it's from Canada (it complies with Canadian ICES-003, is a Class B digital apparatus, etc. standard junk).
It has a dc input only jack, two battery slots for AA alkaline (so you could use either or), and the circuit board with the four components (I really suspect a really small 555 timer under the black glob). No diodes except for the output portion (which seems to have its own issues, but is not the subject of this discussion).
When it doesn't work, I find that I cannot get a voltage reading at all across the capacitor (which is in series with the switch and dc power jack). I can get it across the batteries (singularly and in both together, across the switch when it's closed, and across the jack when the switch is closed). Since it cannot get across the capacitor when it doesn't work, I cannot get a voltage reading anywhere else. If I try to read across one lead of the capacitor and then another (with respect to ground) and then try again on the first lead I tested, it starts working. For a while. If I leave the circuit alone until tomorrow, I'm sure I could come in and it wouldn't be working. There are no loose solder joints anywhere, everything is connected really well and there are no bridges.
I'm thinking it might be the switch (a really cheap slide type), but again, I cannot force it to fault no matter how much I fiddle with it. I'm about to start pulling out my hair over this (and has me distracted now from my regular work).
Ideas? Thoughts? Criticisms for Canadian Class B digital apparatuses?
There is no identification as to the manufacturer (I wouldn't want to claim it either, honestly) anywhere on the case, only an FCC tag stating it's from Canada (it complies with Canadian ICES-003, is a Class B digital apparatus, etc. standard junk).
It has a dc input only jack, two battery slots for AA alkaline (so you could use either or), and the circuit board with the four components (I really suspect a really small 555 timer under the black glob). No diodes except for the output portion (which seems to have its own issues, but is not the subject of this discussion).
When it doesn't work, I find that I cannot get a voltage reading at all across the capacitor (which is in series with the switch and dc power jack). I can get it across the batteries (singularly and in both together, across the switch when it's closed, and across the jack when the switch is closed). Since it cannot get across the capacitor when it doesn't work, I cannot get a voltage reading anywhere else. If I try to read across one lead of the capacitor and then another (with respect to ground) and then try again on the first lead I tested, it starts working. For a while. If I leave the circuit alone until tomorrow, I'm sure I could come in and it wouldn't be working. There are no loose solder joints anywhere, everything is connected really well and there are no bridges.
I'm thinking it might be the switch (a really cheap slide type), but again, I cannot force it to fault no matter how much I fiddle with it. I'm about to start pulling out my hair over this (and has me distracted now from my regular work).
Ideas? Thoughts? Criticisms for Canadian Class B digital apparatuses?
