I bought by mail a couple of twin piezo pickups. On inspection I found the cables connecting the discs to the pots to be so long that I couldn't install them into the narrow profile cigar box. As I had a spare unit to use as a pattern at I decided to cut all the original cables and solder much lighter, shorter ones in their place. Feeling very proud of my work I put everything together and tuned the guitar only to find it sounds fine as acoustic but no effect with the amp. I have checked the pre- and amps work fine so the fault is in my soldering (?).
Is there a way to find where the fault may be? Should I cobble together a battery powered circuit ....... or should I be swatting up on how to use a multimeter. Many thanks.
(Isn't this a fab site So much info!)
What do the solder joints look like? Shinny or dull gray? Shinny is good, dull needs to be redone. Do you have a meter, harbor freight has them cheap! Did you keep the iron on the joints for any amount of time(more then 5 sec) if so it's possible that you cooked them. Post some pics.
Post a pic of your meter.
Hi Will and thanks for your interest. The joints look nice and shiny to me, and I was careful not to have the iron on the points for too long although it isn't thermostatic and does get fairly hot. Hopefully the attached pics help and are clear enough.
No pics. Use the little icon that looks like a mountain than attach file, where it says pixel width, type in 150 then ok. Do that for each one. It is possible that you got crappy Piezos, it happens. Double check your polarity. The wire in the center(+) of the Piezo goes to the center lug of the plug and the one on the edge(-) goes to the ground lug, if those are bacwards you basically made them useless until rectified.
Thanks for the tutorial; have tested each stage and joint; all seems well. The pots are A500K and B500K made by Dilwe. The small tab (resistor?) on the Tone pot has no text and the original advert on Amazon does not specify its rating. If the hardware is near enough OK, is it possible the discs could be better placed? One is directly under the bridge, the other about 3 inches up the neck but within the box as per picture. I remain grateful for your interest.
Have you tested through the pots? Your locations are ok. Do you have a way to un solder your leads from the pots and solder direct to a output jack then plug into your amp? Also check your patch cord. As a matter of fact try that first!
it is possible you have damaged the piezos themself if you put too much heat into them.
put your meter on the 200mV scale and put the leads across the solder points of the piezos. now tap the piezo, not too hard and see if you get any reading on the meter.. you might have to drop to a smaller range. if you get nothing then its the piezo.
Thanks Tim, I couldn't give advice on testing piezos, because I didn't know, never dealt with them prior to building CBGs. Now I know. But I do suspect the Piezo, I "cooked" my first one thinking that they were indestructible. I also thought the same thing about 2032 button batteries, talk about pissing your pants! I'm glad I had my now defunct inspection magnifying light in front of my face. It definitely would have hurt.
Two good ideas, tks guys. They will have to wait until I get a new battery for the multimeter, though ! (thinks......how do I test the battery of a multimeter with a multimeter? Pls don't answer!)