On 07/09/2019 03:05 PM, peter bunge wrote:
Does anyone have a TDK 114H1 common mode choke. At least that is what I
think it is, see schematic below.
This is at the input of the floating power supply in an HP4192A LF
impedance analyzer. I was looking for the short that blew out the 700v
transistors and was confused to find the +5v, +15v, and -15v power
supplies all seemed to be shorted to ground. I did not believe there
could be 3 shorted capacitors nor could I believe that T3 had all
windings shorted together but that is what my ohm-meter was telling me.
I removed it and yes all windings are shorted together, one winding is
ground.
If no one has one how about suggestions? Wind four wires on a small
toroid, varnish, and install? I think it is a common mode choke and
needs the ground return to go through it to cancel the field generated
by the DC currents. I don't think it is critical and, given the second
one in series, I might not notice a difference with just jumper wires,
or wires through a ferrite bead. I am surprised at the lack of small
capacitors, just many aluminum electrolytics.
If all the wires are shorted together, the choke got awfully hot, so you
need to find out what load got shorted and burned it out. It may
still be shorted. I would think that you could wind your own replacement, but you need to find the problem first.
--doug, WA2SAY, retired RF engineer
