saxtim
Well-known member
I'm hoping someone can help me with winding an autotransformer. I had some tips ages ago at the old place, but the thread is long gone. It's for a U87ai mic clone, the schematic can be found here:
http://www.omnipressor.com/MicSchLib/u87ai.gif
The inductor in question is in the DC-DC converter.
I've spent the last couple 6 months on and off on this project and I've now designed/etched/stuffed the PCBs, soldered everything up and it's more or less ready to go bar the autotransformer (and a suitable capsule - another story).
I've got a toriod core with an AL value of 2770nH. It's 16mm in diamater. I've also got some thin magnet wire (I think .25mm from memory).
Bo Hansen has penciled in the values for the inductor on the schematic, but I'm not sure of the units - it looks like micro henries? I know it was mentioned sometime ago at the old place when this was orignally being discussed but I can't remember.
Anyway I have some questions about winding etc:
1. Will it actually matter that much if I don't get the same inductance values? I remember Jacob mentioning that I should just trying winding something like x+2x turns and seeing what voltages were generated. Any suggestions what number of turns to start with?
2. Does it matter if the individual windings contact each other, or should each turn round the core be separated slightly from the last?
3. Its just one long continous winding around the core I need right? I don't need a second winding over the top do I?
4. How do I make the connection for RT? With GE and GN, because they're at the start/end there is extra magnet wire to play with to solder connections to. But for RT, I was fiddling around today and I had great difficulty trying to solder a wire onto the actual loops on the coil, the magnet wire seemed to not like be soldered to and my connections would simply break off if they were knocked - is there a trick for this?
thanks
tim
Thanks
tim
http://www.omnipressor.com/MicSchLib/u87ai.gif
The inductor in question is in the DC-DC converter.
I've spent the last couple 6 months on and off on this project and I've now designed/etched/stuffed the PCBs, soldered everything up and it's more or less ready to go bar the autotransformer (and a suitable capsule - another story).
I've got a toriod core with an AL value of 2770nH. It's 16mm in diamater. I've also got some thin magnet wire (I think .25mm from memory).
Bo Hansen has penciled in the values for the inductor on the schematic, but I'm not sure of the units - it looks like micro henries? I know it was mentioned sometime ago at the old place when this was orignally being discussed but I can't remember.
Anyway I have some questions about winding etc:
1. Will it actually matter that much if I don't get the same inductance values? I remember Jacob mentioning that I should just trying winding something like x+2x turns and seeing what voltages were generated. Any suggestions what number of turns to start with?
2. Does it matter if the individual windings contact each other, or should each turn round the core be separated slightly from the last?
3. Its just one long continous winding around the core I need right? I don't need a second winding over the top do I?
4. How do I make the connection for RT? With GE and GN, because they're at the start/end there is extra magnet wire to play with to solder connections to. But for RT, I was fiddling around today and I had great difficulty trying to solder a wire onto the actual loops on the coil, the magnet wire seemed to not like be soldered to and my connections would simply break off if they were knocked - is there a trick for this?
thanks
tim
Thanks
tim