My nephew was home for the holidays and asked me to look at his acoustic electric bass that stopped "electricing".
The bass is an older Sam Ash product that is remarkably similar to this Dean http://www.music123.com/Dean-EAB-Acoustic-Electric-Bass-519943-i1150843.Music123 (http://www.music123.com/Dean-EAB-Acoustic-Electric-Bass-519943-i1150843.Music123) The electric system is an under saddle piezo pick-up coupled to a 3 band EQ with presence. So. as I said there is no electric output. I did power up the pre amp and probed ~8.5 volts at the 4558 op amp. I suspect that there is a problem with the piezo so that leaves me with this question for you.
How can I drive the pre-amp without the pickup? just to verify that the pre is/isn't working? The pre-amp is all smd and a no-name device. Well. It is stamped Maxwood MQ-1440. Not Fishman or baggs....
tia
-Keith
any failure mode diagnostic suggestions are appreciated.
If you can hook up a signal generator with probe leads and stick them in there. That's about all I can think.
Figure out where the piezo attaches to the piezo and poke it with your finger with the guitar plugged into the amp. You should hear a sound that is like touching the end of a guitar cable.
Zach
Quote from: The Iron Chef on January 02, 2009, 08:18:48 PM
My nephew was home for the holidays and asked me to look at his acoustic electric bass that stopped "electricing".
The bass is an older Sam Ash product that is remarkably similar to this Dean http://www.music123.com/Dean-EAB-Acoustic-Electric-Bass-519943-i1150843.Music123 (http://www.music123.com/Dean-EAB-Acoustic-Electric-Bass-519943-i1150843.Music123) The electric system is an under saddle piezo pick-up coupled to a 3 band EQ with presence. So. as I said there is no electric output. I did power up the pre amp and probed ~8.5 volts at the 4558 op amp. I suspect that there is a problem with the piezo so that leaves me with this question for you.
How can I drive the pre-amp without the pickup? just to verify that the pre is/isn't working? The pre-amp is all smd and a no-name device. Well. It is stamped Maxwood MQ-1440. Not Fishman or baggs....
tia
-Keith
any failure mode diagnostic suggestions are appreciated.
Take a look at the Cirgar Box Guitar guys. They will run the piezo straight into an amp with NOTHING in between. It doesn't sound like an accoustic, but it's not supposed to. There are many sites with schematics and MANY vids on YouTube if you want to hear how it sounds.
Regardless, a garden variety under saddle should make at least some guitar like sounds if plugged direct. It just won't sound pretty.