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Author Topic: Filter Choke in Center Tap of Supply  (Read 3886 times)
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W1KSZ
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« on: February 21, 2022, 01:28:54 PM »

The Filter Choke in an Eico 720 Xmtr seems to have developed a short to the frame. It only
occurs at high voltages in excess of 500 VDC. Below that it seems OK.

I seem to remember that in HV supplies, the Filter Choke was placed in the CT lead of the
Xfmr so that you didn't need a Choke with a high working voltage.

Not sure where I saw that. Can anyone help refresh my memory ?

Tnx es 73, Dick, W1KSZ
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Jim, W5JO
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« Reply #1 on: February 21, 2022, 05:47:59 PM »

Don't know where you saw it but was common practice.  My GK 500 is wired that way.
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WD8BIL
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« Reply #2 on: March 07, 2022, 09:06:14 AM »

OR just mount the choke on insulators of some kind to keep the case/core off chassis ground.
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W1KSZ
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« Reply #3 on: March 07, 2022, 09:39:49 AM »

It's even worse than that ... further investigation shows shorted turn(s)
in the HV Secondary.

Looks like this EICO 720 has become an organ donor.

73, Dick, W1KSZ
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DMOD
AC0OB - A Place where Thermionic Emitters Rule!
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« Reply #4 on: March 07, 2022, 12:44:31 PM »

It's even worse than that ... further investigation shows shorted turn(s)
in the HV Secondary.

Looks like this EICO 720 has become an organ donor.

73, Dick, W1KSZ

Love the 720.

BY now I would think the PS needs a complete revamping.

if you are going to keep it and operate it I would remove the tube rectifier (with its heat), solid state the PS, remove the old PS choke, and use a capacitive filter supply. One could use an equivalent Hammond transformer in place of the EDCCOR.

Phil - AC0OB

* 600V+ HV with EDCOR XPWR065 Transformer.pdf (41.09 KB - downloaded 196 times.)
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Charlie Eppes: Dad would be so happy if we married a doctor.
Don Eppes: Yeah, well, Dad would be happy if I married someone with a pulse.NUMB3RS   Smiley
W1KSZ
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« Reply #5 on: March 07, 2022, 11:14:25 PM »

Tossing another $150+ into this is not what I want to do.
I'll just write this one off.

Besides the Multi-Elmac Transmitter is a far better radio in a
much smaller package. I have three of them, one a daily user.

73, Dick, W1KSZ
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DMOD
AC0OB - A Place where Thermionic Emitters Rule!
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« Reply #6 on: March 07, 2022, 11:18:42 PM »

Tossing another $150+ into this is not what I want to do.
I'll just write this one off.

Besides the Multi-Elmac Transmitter is a far better radio in a
much smaller package. I have three of them, one a daily user.

73, Dick, W1KSZ

Then you could possibly sell it to someone who will upgrade it.

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Charlie Eppes: Dad would be so happy if we married a doctor.
Don Eppes: Yeah, well, Dad would be happy if I married someone with a pulse.NUMB3RS   Smiley
W1KSZ
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« Reply #7 on: March 08, 2022, 03:53:04 PM »

That's probably the best thing to do with it. Prefer to sell it locally
as packing and shipping are a real pain.

73, Dick, W1KSZ
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