So it was time to continue the piezo preamp project. I had the faint recollection that something was missing and the build wasn’t finished completely when I put it together. I hooked up the piezo and the audio jack using alligator clips and I put cable from the audio jack to my audio interface. I started Reaper and set ip up for recording. Then I connected the battery to the preamp and started tapping the piezo and nothing happened. Then I started to troubleshoot the preamp by looking at the schematic type of thing and it wasn’t long until I noticed that the battery plus was not connected to the op-amp so there was no supply current coming into the IC. I got my soldering iron and solder and fired up the station. I cannot keep the soldering iron connected to the station all the time because of our cats. I can’t keep any wires visible for that matter I have to hide them all as well as possible. So I finally got the soldering station set up and heating up, I managed to hit the power switch on the extension cord shutting everything down I had hooked up on it including my computer. I finally got the missing wire soldered which was little difficult because I hadn’t soldered anything for over a month or two. I hooked up all the cables again and tested the setup with Reaper and I got something coming in so I recorded it. I could here some tapping because I tapped the piezo. Here are some pictures about the situation:
As you can see poor soldering quality is my trademark. I tapped the piezo while hooked up to the audio interface and I turned the gain quite high so I could here the tapping. I noticed that I picked up signal only when I tapped the piezo directly. Nothing was picked up when I tapped next to it. I am not sure if it really works. One thing is certain that it works in the sense that everything is soldered and the solder joints are good. Since this device is a preamp meant for real amplifier I need to take it to the studio and connected it to a real guitar amp to see what I can get out of it. If it happens to work there then I can continue the layout design for the enclosure so I can wrap it up.
Testing the device at the studio with real guitar amplifier gave same results. Not giving a sound unless really tapping the piezo. Time for troubleshooting! The first thing I decided to do is visually inspect that everything is there and the paths goes the right way. At first I though that I had forgotten one connection, but turning the perfboard around I noticed that the connection was there. Visual inspection passed so next step was continuity testing and I tested random points and they all passed. Too lazy to hook up battery into the device I thought that next step would be ohm measurement. I got results from the 1k and 2k voltage divider part, but the 2.220M voltage divider I was unable to get real results. I noticed that this one meter I have, given to me by a friend, had 20M range do I could use that. My right hand is not in good shape due to my physical constraints so I was not satisfied with the measurements. This is something I have to do again using alligator clips to get a good grip and that is what I will do next.
I got the alligator clips connected and I tried to measure the resistor, but could not get a reading the meter did not show a constant value, or constant enough. I think the battery might be running out and I could not get the battery hatch open. Time passed and I did nothing. I did manage to buy a new multimeter and I thought that this time I will not buy one of those cheap chinese meter, but a more known brand. I almost did buy a UNI-T meter, but due to this one video which reviewed the Victor VC921 a cheap chinese meter, but the review was quite convincing. This is my first auto ranging meter and it can go up to 40M so I was able to measure my resistors because they seemed like the most probable cause. But they were quite on the spot, 2.223M ohms both, so what to do next is a good question. I might double check that the IC is connected correctly or I could simple scrap the project at least for now.
I haven’t worked on this project for a while or any other project for that matter and for now I will scrap it. I thought that this blog would inspire me to be more active about these projects, but that did not happen. It might be due to fact that I have been very very tired and I have not had the strength to do anything, I’ve had a really strong fatigue. The reason for this and the fact that my condition has gone down hill quite rapidly during the past six months is now starting to see light of day. It is a long progress to get the diagnose, but with very strong indications that I will have someday the diagnose of MS-disease. So for the time being I will not be updating any of my blogs and probably wont be doing any electronics projects for a while. I might have had MS for the past five to eight years undiagnosed at least if I look at the symptoms.
P.S. This was a good day for a post because it is my sons 6th birthday! Happy Birthday Onni!