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WTB a TDK 114H1 common mode choke

 

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.?
 

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
 

Is the choke wound with fairly thin wire? It would be unusual for a CM choke to have all its windings shorted together unless it got very hot from fault current or adjacent heat sources, or by serious over-voltage between the windings. I'd recommend leaving out the choke and just jumping the lines until the cause is figured out. Rewinding or replacing the choke later should be fairly easy.

Ed
 

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.??
TDK114H1.jpg

On Tue, Jul 9, 2019 at 7:16 PM doug <dmcgarrett@...> wrote:


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
 

Thanks Ed. See my other reply with photo. I think a pair of windings shorted and burnt the insulation off the other windings and caused all to short together. It must be thin wire on a toroid and now a melted blob of less than an ohm between any two pins with no pins open.?
I suggest NOT following the manual where it says to disconnect the collector of the overcurrent sense transistor to disable the protection. It is safer to look for a short with an ohm meter. In this case all six rectifiers in the?+5v,?+15v, and -15v supplies appeared to be shorted (less than an ohm). I did not believe that and looked elsewhere. Pulling a connector indicated the short was off the main power supply board but still did not make sense. One shorted capacitor is not surprising, two shorted capacitors unlikely, three shorted capacitors better start thinking something different. The resistance went up as I moved away from the choke. Four shorted windings in a choke seemed impossible and I expected to find the choke OK but had to remove it to check further.?
Anyway still looking for a spare before trying to wind one. I don't like the idea of four windings touching even if varnished. Formvar is good but can it be trusted? I suppose all windings touch adjacent wires in any transformer.
PeterB

On Tue, Jul 9, 2019 at 10:33 PM Ed Breya via Groups.Io <edbreya=[email protected]> wrote:
Is the choke wound with fairly thin wire? It would be unusual for a CM choke to have all its windings shorted together unless it got very hot from fault current or adjacent heat sources, or by serious over-voltage between the windings. I'd recommend leaving out the choke and just jumping the lines until the cause is figured out. Rewinding or replacing the choke later should be fairly easy.

Ed

 

Here's a datasheet:?.
Looks like 1:1:1:1 CM coil, maybe coilcraft have something similar?

On Tue, Jul 9, 2019, 7:06 PM peter bunge <bunge.pjp@...> 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.?

Attachments:
 

Thanks Siggi. How did you find that? My search turned up nothing.
It is as I suspected but now I know what inductance to aim for.
I'm still hoping to find one. There must be a stash somewhere.
Peter

On Wed, Jul 10, 2019 at 12:42 PM Siggi <siggi@...> wrote:
Here's a datasheet:?.
Looks like 1:1:1:1 CM coil, maybe coilcraft have something similar?

On Tue, Jul 9, 2019, 7:06 PM peter bunge <bunge.pjp@...> 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.?

Attachments:
 

On Wed, Jul 10, 2019 at 20:57 peter bunge <bunge.pjp@...> wrote:
Thanks Siggi. How did you find that? My search turned up nothing.

Just some Googling and then clicking through a couple of times. Many of those datasheet collection sites seem quite sketchy, so I generally don¡¯t look there unless manufacturer and supplier sites come up empty.

Good luck on finding or making a substitute.

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