Jalopy wrote:So... having received a shipping confirmation today and having reviewed the concerns regarding vactrols - How can one test a vactrol before committing it to the build? I read the page 22 in the PS3100 thread linked in the above post and did not see it explicitly discussed.
Thanks!
Good question really....I haven't thought that far through since I haven't had any issues myself but lets figure it out shall we?....
It's probably real easy to test them first rather than have to desolder them and fiddle with all that troubleshooting.... I normally test all components while I'm building modules before soldering them into place..
After reading the Ps3100 thread I posted again and thinking about what makes a vactrol, I'm guessing that a way to test a vactrol would be to supply a voltage to the LED and then test the resistance of the LDR. I'm not sure how much you know about electronics so, I'll break it down for everyone, eh?
I'm no expert but I know a little...
LEDs have polarity and probably require a maximum of 3 volts.. So, One could find the polarity of the LED side of the vactrol by doing a continuity test with a multimeter... Vactrols usually have a marking on them to indicate polarity, and if you know how to identify that then you won't need to do a continuity test. However a continuity test will also identify a working or faulty LED... When you know which leg of the LED is positive and which one is negative, then you could probably touch those legs to the positive and negative sides of a 3V coin cell battery...
The LDR (Light Dependent Resistor) side of the vactrol is not polarity dependent. So then you could use a multimeter to test the resistance while the LED has a charge from the coin cell battery. If they all test out to be around the same resistance then they are probably good... If one of them tests out to have a lot more resistance then the others then maybe the resistance is too much to let enough light through to the rest of the circuit...
Here is the quote from the other thread, and I've put in bold some of the important clues:
davebr wrote:
Then you can just tack another one in and see how it differs. I didn't write down the actual resistance but a "good" one at whatever voltage/current I ran them at was a couple of hundred ohms, say 190ohms. The "bad" one was a couple of K ohms, like maybe 2300ohms. It was a big difference. I've matched vactrols before for some of the Buchla builds and I never saw that much of a difference. It was always something like 2X, not 10X.
Dave
So,I'm also guessing that the current supplied to the LED is not critical that it is 3V.. Just
DON'T go over 3V... So if you don't have a 3V coin cell battery lying around you could use a single AA or AAA battery as they are 1.5V... The important thing here is that you use the same battery to test the Vactrols(same Volts)...
I haven't looked at the Vactrol datasheets and
I don't know what voltage they need to function... I'm just guessing about the voltage and erring on the safe side.. So, looking at the datasheets is always advised when testing or understanding components...
As I said, I'm not expert, but I hope this helps... Any Pedantic rants and or corrections about my testing method are welcome as I just made it up as I was going along.....
Receiving bad vactrols is not as common as one might think. Now that a few wigglers "might" have received these bad vactrols, it could be safe to assume that the quota of bad vactrols have been fulfilled and no one else will have these problems..
