Some months ago I found a deal on a used Microphone Tester. It is like the Super Star T747 but it is branded "Alan" which I THINK I have heard is some kind of French connection to Midland. When I got it ... it didn't work at all. Soon tracked that to the ground lead on the 9V battery clip broken off of the PCB. Soldered that back in place then hot glued a good dot to hold the 9V battery leads in place.
Pushed in a standard Cobra 4 pin microphone. The TX/RX lights worked but no sound came through at all. I say no sound came through..... when I turned the volume pot you could hear "scratchiness"...but no audio from the microphone made it in.
I went ahead and desoldered all of the connector pins and removed the PCB so I could a) trace the circuit out and b) just see what parts were there.
I now have a pencil whipped schematic of the whole thing (and there isn't much! A standard LM386 chip hooked up, two LEDs ... one green...one red... and all of the copper connections between the mic jacks.
I have to get an audio source hooked up but I am going to do that to do further testing and make sure that sound IS getting passed through and amplified.... but as big of a PITA as disassembly is.... I think since there are only 4 electrolytic caps I am going to just replace them before putting it all back together......AND pipe some signal THROUGH it just to make sure that everything is working BEFORE resoldering it all together.
Pushed in a standard Cobra 4 pin microphone. The TX/RX lights worked but no sound came through at all. I say no sound came through..... when I turned the volume pot you could hear "scratchiness"...but no audio from the microphone made it in.
I went ahead and desoldered all of the connector pins and removed the PCB so I could a) trace the circuit out and b) just see what parts were there.
I now have a pencil whipped schematic of the whole thing (and there isn't much! A standard LM386 chip hooked up, two LEDs ... one green...one red... and all of the copper connections between the mic jacks.
I have to get an audio source hooked up but I am going to do that to do further testing and make sure that sound IS getting passed through and amplified.... but as big of a PITA as disassembly is.... I think since there are only 4 electrolytic caps I am going to just replace them before putting it all back together......AND pipe some signal THROUGH it just to make sure that everything is working BEFORE resoldering it all together.
