Tweet
So far I have successfully built the Rev D MPP to work with a commercial "Miner John" 6" Mono Folded TDI coil. My board is running at 14.8V using the Panasonic 18650 batteries and the coil specs are 310uH @ 2.20 ohms. The issues started when I modified the board using the KRinAz mods and I am not sure what is happening here. When I first ran the detector, the audio was not steady as it was before the mod. In other words, the audio (using a 3" 8 ohm speaker) was chirping, not a steady tone as before then after several runs, the sound quit but I could hook up my earphone and I could still here a faint chirping sound. I checked my audio Threshold pot connections but that did not resolve the issue. My next check was the voltage at PL5 and that checked out at +4.98V and -4.97 at pins 1 and 3 but turning the audio threshold 10K pot did not change the pitch. However pin 2 (middle) the voltage was all over the place ranging from 13.1 to -.86Volts. Immediately I suspected U10 (NE555) so I hooked up my O'scope to the output before R38 (680 ohm) and I got a square wave that appeared to have a lot of noise. I am not sure how to interpret or diagnose what I am looking at. I am attaching a screenshot of the NE555 output in hope one of the Forum members can point me in the right direction. Any suggestions would be immensely appreciated.
-
-
Try adjusting the Trigger level on the scope . Looks like it's trying to trigger on a Harmonic. -
homefire, good point, missed that. I will try it again when I get home from work.Comment
-
Well so much for help from the forum! not a word but I was able to find and fix the problem. It turns out two issues, one, an out of tolerance trimmer (cheap) and second, the coil was wired incorrectly. Had somehow switch the ground and Tx pins on my connector. Detector working beyond expectations and almost rivals in depth my friend's White dual field detector.Comment
-
Good stuff. Did the Triggering thing help ?Comment
-
Yes not sure why I did not set trigger on channel 1, guess I was frantically looking all over the place until I sat down with pencil and paper and retraced my steps. Something as simple as wrong coil wiring will throw you off big time. I am in the industrial controls design Engineer and no experience in MD but just started getting into MD building kick. My son is an EE major and has also taken an interest in building MD's besides our hobby of prospecting mainly for gold and meteorites.
But a Big Thanks! Homefire for you kind help!Comment
-
Glad to hear you got it fixed Hector, nice job..Comment
Comment