Ok, this kit is so simple, I cannot believe I’m here, but…
I bought 3 MK108 kits. I built one. It doesn’t work. I double-checked the (whopping) 4 components, everything looks fine; so I’m thinking a bad transistor.
I built a second one; exact same results… ok likelihood of two kits with bad parts, slim to none.
It seems like bad transistor(s)!? If I short across the transistor on the buzzer’s path, it buzzes.
I tested the transistor across the “water switch” path with a multimeter (diode mode), and it looks good, and in the correct direction.
The transistor is definitely mounted as per the PCB’s silkscreening, which jives with the meter test. Yet it’s behaving as if the transistor is not connecting the buzzer to ground (-) regardless of the “switch” (I connected the two water contacts with alligator clips to simulate water).
I avoided the conductive liquid issue by simply connecting the liquid contacts via wire (alligator clips).
I double (now triple) checked the resistors (both kits); they’re correct. R1 (Brown black Orange) above/left of buzzer. R2 (yellow purple yellow) right of buzzer, next to T1 (flat side towards edge of PCB, round side towards buzzer).
No, on the transistor replacement; I figured it was unlikely that I received TWO kits with bad transistors (or that I would have fried them both while mounting them).
I have a third kit; I could try that one…
You’d think after I successfully build a Nixie tube clock, I could put this together. :?
I have built one of these kits and had the same problem that you are having as well.
What I found is either the silk screen is wrong or there was a parts change with T1.
If you mount T1 180 degrees out (backwards from the print on the board) this will make it work.
We have taken a couple of random samples from our warehouse and we’ve assembled them. They all work fine, so we assume there must have been a couple of different transistors in a large batch of BC517.
We did not receive any complaints so far.
We apologize for this inconvenience which is totally beyond our control.
If you supply an address, we will be happy to send a spare transistor.
I wondered about that; it seemed to be the only possible problem, but I was thought I’d tested the leads properly, verifying the orientation matched the schematic… obviously not.
So, the PCB has the silkscreening for T1 backwards. Flip T1 around, and voila!
THANKS.
(p.s., yes, it’s a BC517)
[quote=“Wrong Way”]TimeFrame,
I have built one of these kits and had the same problem that you are having as well.
What I found is either the silk screen is wrong or there was a parts change with T1.
If you mount T1 180 degrees out (backwards from the print on the board) this will make it work.
I’ve got a similar problem to the OP. Tried 2 of these kits and neither work. Shorting the buzzer did work so I tried reversing the transistor but now nothing at all. Suspect the transistor has blown with all the heat from desoldering but any suggestions gratefully received.
Hi,
New to this forum.
I to could not figure out why the water alarm was not working.
Thanks to this forum I was able to see that you had to turn the T1 around and now it works. I have more of these kits on order so I suppose that the future kits will be screened the same wrong way? That’s OK as long as I know to turn the T1 180 out.
