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Zenith H725
#69

I got into the first AM IF can today, and found its mica was cracked. Amazing that it was still working. This one makes up three capacitor sections 120 pF, 120 pF and 240 pF. The last two share a common plate.  Fortunately, I had suitable silver mica caps on the shelf. I cut some sections of insulating sheet to replace the original mica, so the contacts don't short out, and reassembled with the new capacitors concealed in the can. I find there are three or four stages of note taking beginning with the basic chassis wiring and orientation of the can, then recording to which tags the wires of each coil are attached, and lastly the arrangement of contacts to pads on the mica sheet, orientation of the mica etc., quite time consuming.

Figuring what should go where for cap substitution was tricky, and reference was made to the schematic, and the original mica's silver pads to get the configuration correct. Thankfully after getting it back together, the radio was still receiving AM, and IFT1 peaked up cleanly on the signal generator.

Of course, it still crackles and crashes because the problem is in IFT2 Icon_lol

But at least I didn't end up in a worse situation than I started - there was some fear that I'd mix up connections or miss something, and end up with a dead radio.

I see that the last remaining AM IFT has three coils and three capacitor sections, so more delicate surgery lies ahead.  Icon_eek. One thing I figured out was a good way to hold the parts while resoldering wires and caps into the can.

I don't hold with furniture that talks.


Messages In This Thread
Zenith H725 - by EdHolland - 03-17-2025, 09:45 PM
RE: Zenith H725 - by MrFixr55 - 03-17-2025, 10:24 PM
RE: Zenith H725 - by EdHolland - 03-18-2025, 11:52 AM
RE: Zenith H725 - by David - 03-18-2025, 01:48 PM
RE: Zenith H725 - by EdHolland - 03-18-2025, 06:09 PM
RE: Zenith H725 - by Arran - 03-18-2025, 10:08 PM
RE: Zenith H725 - by RodB - 03-19-2025, 10:04 AM
RE: Zenith H725 - by EdHolland - 03-19-2025, 10:46 AM
RE: Zenith H725 - by morzh - 03-19-2025, 12:38 PM
RE: Zenith H725 - by RodB - 03-19-2025, 12:55 PM
RE: Zenith H725 - by morzh - 03-19-2025, 01:25 PM
RE: Zenith H725 - by David - 03-19-2025, 03:49 PM
RE: Zenith H725 - by Arran - 03-19-2025, 04:45 PM
RE: Zenith H725 - by Paul Philco322 - 03-19-2025, 08:13 PM
RE: Zenith H725 - by EdHolland - 03-20-2025, 12:34 PM
RE: Zenith H725 - by MrFixr55 - 03-20-2025, 12:59 PM
RE: Zenith H725 - by EdHolland - 03-20-2025, 08:40 PM
RE: Zenith H725 - by MrFixr55 - 03-21-2025, 08:59 AM
RE: Zenith H725 - by radiorich - 03-21-2025, 09:29 AM
RE: Zenith H725 - by EdHolland - 03-21-2025, 09:41 PM
RE: Zenith H725 - by MrFixr55 - 03-21-2025, 09:53 PM
RE: Zenith H725 - by EdHolland - 03-22-2025, 03:17 PM
RE: Zenith H725 - by EdHolland - 03-22-2025, 06:09 PM
RE: Zenith H725 - by RodB - 03-22-2025, 06:52 PM
RE: Zenith H725 - by Arran - 03-22-2025, 07:05 PM
RE: Zenith H725 - by MrFixr55 - 03-22-2025, 08:34 PM
RE: Zenith H725 - by EdHolland - 03-22-2025, 08:40 PM
RE: Zenith H725 - by radiorich - 03-22-2025, 10:22 PM
RE: Zenith H725 - by radiorich - 03-22-2025, 10:35 PM
RE: Zenith H725 - by MrFixr55 - 03-22-2025, 10:39 PM
RE: Zenith H725 - by radiorich - 03-23-2025, 12:17 AM
462ron - by 462ron - 03-23-2025, 08:54 AM
RE: Zenith H725 - by Paul Philco322 - 03-23-2025, 09:18 AM
RE: Zenith H725 - by EdHolland - 03-23-2025, 10:37 AM
RE: Zenith H725 - by radiorich - 03-23-2025, 11:31 AM
462ron - by 462ron - 03-24-2025, 08:22 AM
RE: Zenith H725 - by radiorich - 03-24-2025, 08:34 AM
RE: Zenith H725 - by EdHolland - 03-24-2025, 02:44 PM
RE: Zenith H725 - by EdHolland - 03-24-2025, 06:56 PM
RE: Zenith H725 - by radiorich - 03-24-2025, 10:33 PM
RE: Zenith H725 - by EdHolland - 03-24-2025, 10:46 PM
RE: Zenith H725 - by Arran - 03-24-2025, 11:42 PM
RE: Zenith H725 - by EdHolland - 03-25-2025, 11:49 AM
RE: Zenith H725 - by Arran - 03-25-2025, 06:40 PM
RE: Zenith H725 - by EdHolland - 03-25-2025, 06:42 PM
RE: Zenith H725 - by EdHolland - 03-25-2025, 09:13 PM
RE: Zenith H725 - by radiorich - 03-26-2025, 01:02 AM
RE: Zenith H725 - by EdHolland - 03-27-2025, 10:57 AM
RE: Zenith H725 - by EdHolland - 03-27-2025, 04:25 PM
RE: Zenith H725 - by EdHolland - 03-27-2025, 11:08 PM
RE: Zenith H725 - by EdHolland - 03-28-2025, 03:45 PM
RE: Zenith H725 - by EdHolland - 03-28-2025, 09:53 PM
RE: Zenith H725 - by radiorich - 03-29-2025, 01:27 AM
RE: Zenith H725 - by MrFixr55 - 03-29-2025, 02:33 PM
RE: Zenith H725 - by David - 03-29-2025, 06:28 PM
RE: Zenith H725 - by EdHolland - 03-31-2025, 12:16 PM
RE: Zenith H725 - by rfeenstra - 03-31-2025, 02:37 PM
RE: Zenith H725 - by RodB - 03-31-2025, 02:41 PM
RE: Zenith H725 - by EdHolland - 03-31-2025, 03:03 PM
RE: Zenith H725 - by EdHolland - 04-02-2025, 06:42 PM
RE: Zenith H725 - by EdHolland - 04-02-2025, 08:39 PM
RE: Zenith H725 - by Arran - 04-02-2025, 11:42 PM
RE: Zenith H725 - by radiorich - 04-03-2025, 12:19 AM
RE: Zenith H725 - by EdHolland - 04-03-2025, 10:18 AM
RE: Zenith H725 - by EdHolland - 04-04-2025, 06:18 PM
RE: Zenith H725 - by Paul Philco322 - 04-04-2025, 08:27 PM
RE: Zenith H725 - by EdHolland - 04-04-2025, 09:08 PM
RE: Zenith H725 - by radiorich - 04-05-2025, 01:03 PM
RE: Zenith H725 - by EdHolland - 04-05-2025, 06:10 PM
RE: Zenith H725 - by EdHolland - 04-06-2025, 04:04 PM
RE: Zenith H725 - by EdHolland - 04-06-2025, 07:40 PM
RE: Zenith H725 - by Arran - 04-07-2025, 02:34 PM
RE: Zenith H725 - by EdHolland - 04-07-2025, 05:32 PM
RE: Zenith H725 - by EdHolland - 04-08-2025, 05:51 PM
RE: Zenith H725 - by Arran - 04-08-2025, 06:34 PM
RE: Zenith H725 - by EdHolland - 04-08-2025, 08:23 PM
RE: Zenith H725 - by David - 04-08-2025, 08:52 PM
RE: Zenith H725 - by EdHolland - 04-10-2025, 01:43 PM
RE: Zenith H725 - by David - 04-10-2025, 04:06 PM
RE: Zenith H725 - by EdHolland - 04-10-2025, 06:06 PM
RE: Zenith H725 - by EdHolland - 04-20-2025, 05:09 PM
RE: Zenith H725 - by Paul Philco322 - 04-20-2025, 07:13 PM
RE: Zenith H725 - by David - 04-20-2025, 08:47 PM
RE: Zenith H725 - by radiorich - 04-21-2025, 09:43 AM
RE: Zenith H725 - by EdHolland - 04-24-2025, 08:04 AM



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