T3 Transistor – Source terminal Voltage problem BEM-014 – Voltages (before / after) This was needed so that I can find my way around faster, when measuring the voltages, since … I decided I’d like to salvage the device. I had to spend some time to identify the components based on their connections on the board itself and in the schematic: BEM-014 – Annotated Circuit Layout However, the scan of the component layout is very poor and only half of the component identifiers are readable. The available schematic / service manual does show the voltages and they are readable. In the following video it can be seen that the output settles down to a nice sinusoidal, but it starts clipping stronger and stronger as time goes by: BEM014 – Startup ok but clipping afterwards Component layout Thus it wasn’t anymore about lifted traces and moving the components back to their original place – but also, figuring out what is wrong with it. It looked good as the device was powered on, but 2 minutes into the operation it started clipping: Bad output waveform Having a look at the output waveform – it was also problematic. The puzzling thing about the temperatures was that one output transistor was way hotter than the one nearby. I took some temperature readings after letting it on for a while. Upon powering on – the good news was that the device did not blow up – nor any capacitors. Curiosity won though and I powered it on to see if it still works. I still kept wondering weather I should just salvage the capacitor and dispose of the rest. The insert operation affected the quality of the existing pages though. The second one contains few pages more – including the calibration procedure, that somebody seems to have inserted into the original schematic. One that is sharp (I assume the initial one). There are two schematics that I was able to find. Now with a name – it was easy to find a schematic. I decided to use one of the output transistors as criteria, and, after many searches, what do I spot at the END of the search results ? Low-frequency tone generator BEM014 But what was it ? I kept searching Google – but “tone generator” or “audio generator” or “signal generator” were returning too many results. But what is this thing ?!Ĭapacitor was still tempting, it was also tempting to try to repair / salvage the device. It looked more and more like it was an assembled kit – the owner made an error when assembling it – and it was easier to try to salvage the situation by soldering on the back on the circuit board. Some traces were lifted, and some components cut from the main side of the board and soldered on the back. Instead of the solder flowing properly, it looked like smaller blobs melted over smaller blobs. The large solder joints look cold, as made with a not powerful enough iron. The interior hand a stark contrast to the exterior. Very poor soldering Lifted trace Another component missing BEM-014 – Interior, as bought A diode is missing Another angle of Diode Components soldered on the back, including the diode. Who made this thing ? Interior aspect Top left pot turned all the way. The device looked clean – except the top / bottom screws that were missing but more importantly it was the lack of any marking / model.
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