Zenith H725

hardpanman · Posted: Nov Mon 02, 2009 5:45 pm

My Zenith H725 AM/FM has a capacitor (#C28) that connects from the middle post on the volume control to the 19C8 tube. This paper cap is printed with the word GROUND on it and there is a brass hook on the opposite end that has a braided wire to chassis ground. When replacing this cap with a modern Xicon polypropylene coupling capacitor, what can I do about this ground?
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Burnt Fingers · Posted: Nov Mon 02, 2009 7:55 pm

That was probably done to reduce hum pickup. Try the new cap and if there is hum you may have to use a shielded lead to the tube grid.

Carl

jkaetzjr · Posted: Nov Mon 02, 2009 8:03 pm

I think that cap was actually shielded. If problem with regular cap, slip some coax braid over it and ground braid, or any sort of metal, foil, wrap it in spiral wire winding, whatever is handy

hardpanman · Posted: Nov Mon 02, 2009 8:37 pm

I pried open the little metal hook on the opposite end from the word GROUND and it was attached to the foil under the wax cover. That's where the little braided wire was connected and ran to chassis ground. If it hums I try the wrapping trick. Thanks.

gmcjetpilot · Member Joined: 22 Jul 2009 Posts: 433

hardpanman · Posted: Nov Wed 04, 2009 5:29 am

I gambled and ignored the ground, installed the electrolytics, and brought it up in the variac last night. FM is coming in sweet and pure. The first thing I brought up was some gospel music that was astounding in its clarity. Tubes rule!