Welcome Guest! Be sure you know and follow the Phorum Rules before posting. Thank you and Enjoy! (January 12) x

Thread Rating:
  • 0 Vote(s) - 0 Average
  • 1
  • 2
  • 3
  • 4
  • 5

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 - Yesterday, 01:03 PM
RE: Zenith H725 - by EdHolland - Yesterday, 06:10 PM
RE: Zenith H725 - by EdHolland - 5 hours ago
RE: Zenith H725 - by EdHolland - 2 hours ago



Users browsing this thread: 2 Guest(s)
[-]
Recent Posts
Zenith H725
Here's what the inside of AM IFT2 looked like, and the other pic shows the discs I made to take place of the mica and ke...EdHolland — 07:40 PM
Zenith H725
IF2 will need replacement caps. The arcing was severe enough that the mica is pitted and holed where the HT flashed over...EdHolland — 04:04 PM
My Philco 37-116 Restore
Measuring from center tap like the tube voltages show. Cap 127 is isolated from ground. Cap 127 shown in upper left of p...dconant — 08:05 AM
My Philco 37-116 Restore
Are you measuring relative to the centertap or the GND?morzh — 11:57 PM
Philco 610B oscillator wiring
Still not clear on the wiring interface between the 6A7 and oscillator. After refering to the available schematics and s...Tubester — 07:18 PM
Refinishing Ideas
My 37-116 code 121 is the best sounding radio i have...a daily driver. Since we are talking about "changes". ...poulsbobill — 07:18 PM
My Philco 37-116 Restore
Hello, I finally got brave enough to take the cans off the Expander Unit. Got the grid cap wires replaced and back toget...dconant — 06:50 PM
Zenith H725
I got into the first AM IF can today, and found its mica was cracked. Amazing that it was still working. This one makes ...EdHolland — 06:10 PM
Philco model #20
AHH HA , I got it and can’t thank you fellows enough , when I changed the capacitors I took the advice and did not unsol...onlyrick — 02:24 PM
Zenith H725
Hello Ed, yes, I like letting projects run for few days to make sure they don't start acting up . Sincerely Richardradiorich — 01:03 PM

[-]
Who's Online
There are currently 818 online users. [Complete List]
» 1 Member(s) | 817 Guest(s)
Avatar

>