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Title: Filter Choke in Center Tap of Supply Post by: W1KSZ 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 Title: Re: Filter Choke in Center Tap of Supply Post by: Jim, W5JO 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.
Title: Re: Filter Choke in Center Tap of Supply Post by: WD8BIL 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.
Title: Re: Filter Choke in Center Tap of Supply Post by: W1KSZ 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 Title: Re: Filter Choke in Center Tap of Supply Post by: DMOD 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 Title: Re: Filter Choke in Center Tap of Supply Post by: W1KSZ 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 Title: Re: Filter Choke in Center Tap of Supply Post by: DMOD 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. Title: Re: Filter Choke in Center Tap of Supply Post by: W1KSZ on March 08, 2022, 03:53:04 PM That's probably the best thing to do with it. Prefer to sell it locally AMfone - Dedicated to Amplitude Modulation on the Amateur Radio Bands
as packing and shipping are a real pain. 73, Dick, W1KSZ |