Re: WTB a TDK 114H1 common mode choke
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I think the choke started with shorted adjacent windings which soon caused all windings to short together. There is no sign of a short past it now it is removed. It was shorting the +5v, +15v, and -15v supplies together. It is about 3/8" cube like a DIP8 It is probably a toroid with 4 windings. TDK seems to be impossible to contact and have too many catalogs. Is it a coil, transformer, transient suppressor, or? Because it is from 1980 it is probably not in their catalogs and they would have no interest in selling me just one. Keysight may have a spare if no one here has one, or a scrapped HP4192A. There are two on the board but twelve 113G1 which look the same only pins 3 & 4 are missing (so 3 windings). The pin numbering is different from a DIP, see below. You can see the second one and the holes where I removed the bad one which had no signs of damage externally like discoloration, cracks, or swelling.??
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
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