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

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

48-482 no FM
#10

22 ohms would not be unreasonable for a 455 kHz IF transformer coil, but a 9.1 MHz coil should read much lower than that.

Don't be afraid of trying the alignment, as the FM IF will almost certainly need adjustment. Sometimes it is the best way to determine if a problem exists in any of the tuned circuits of an IF stage. If you can't get a definite peak on any particular adjustment, then a problem exists with that related circuit.

I have a 48-482 and found the FM IF to be way out of alignment even though the trimmer adjustments were seemingly previously untouched. The mica compression trimmers have a tendency to drift in capacitance, especially after 70 years.

As to enough signal at 9.1 MHz, 5 mV should be more than enough if injected into the 7F8 grid at test point A. Try the full 5 mV first and see if you get any negative AVC voltage at the point I described previously. Use the minimum signal level into test point A that results in an increase in AVC voltage over the reading with no signal applied. Decrease the signal generator output as each tuned circuit comes into alignment.


Messages In This Thread
48-482 no FM - by rebrands - 09-10-2017, 07:18 PM
RE: 48-482 no FM - by klondike98 - 09-10-2017, 07:57 PM
RE: 48-482 no FM - by Mondial - 09-10-2017, 08:41 PM
RE: 48-482 no FM - by rebrands - 09-10-2017, 09:50 PM
RE: 48-482 no FM - by rebrands - 09-12-2017, 01:35 PM
RE: 48-482 no FM - by robsradioactive - 09-14-2017, 07:23 PM
RE: 48-482 no FM - by rebrands - 09-14-2017, 10:19 PM
RE: 48-482 no FM - by Mondial - 09-15-2017, 12:35 AM
RE: 48-482 no FM - by rebrands - 09-15-2017, 04:28 PM
RE: 48-482 no FM - by Mondial - 09-15-2017, 09:22 PM
RE: 48-482 no FM - by rebrands - 09-15-2017, 10:44 PM
RE: 48-482 no FM - by rebrands - 09-16-2017, 11:06 PM
RE: 48-482 no FM - by robsradioactive - 09-17-2017, 06:38 PM
RE: 48-482 no FM - by rebrands - 09-19-2017, 12:37 AM
RE: 48-482 no FM - by klondike98 - 09-19-2017, 11:01 AM
RE: 48-482 no FM - by robsradioactive - 09-21-2017, 11:36 PM
RE: 48-482 no FM - by rebrands - 09-22-2017, 10:51 AM



Users browsing this thread: 1 Guest(s)
[-]
Recent Posts
Graphics for majestic 1050 dial glass.
Murf; I found this thread on the ARF, the first photo has a pretty good view of the dial glass. Regards ArranArran — 01:12 AM
Zenith H725
hello Ed, how about that speacial tape used for ducting it's like foil or how about thin piece of aluminum roof flash...radiorich — 12:19 AM
Zenith H725
Ed; One material that I have seen, but never tried for this was material for making exhaust gaskets, it's similar to ...Arran — 11:42 PM
Zenith H725
I just remembered, I have some hi temp silicone rubber material which could do the trick. Or a piece of FR4 laminate. Th...EdHolland — 08:39 PM
Zenith H725
The PSU filter cap arrived today (thank you USPS!) so I will work on that later. Meanwhile, I have the dial, speaker...EdHolland — 06:42 PM
Philco 610B oscillator wiring
Thanks Terry. After checking my notes I think I recorded about -10v at the 6A7 G4/control grid. The screen grid (G3 &...Tubester — 05:59 PM
The list of my radio & TV collection!
Magical chords of forgotten melodies, old nostalgic music on an old radio... Saturday night blues on the Mid-Waves on an...RadioSvit — 12:20 PM
Philco 42-345 Restoration/Repair
Thank you MrFixr55 the issue with this radio is that the internal coil antenna is missing and there was a wire in its pl...osanders0311 — 11:34 AM
Philco 610B oscillator wiring
Regarding the oscillator circuit which is comprised of the 6A7's cathode, control grid, and screen grid. These elements ...Radioroslyn — 10:33 AM
Philco 42-345 Restoration/Repair
Hi OSanders, First off, welcome to the Philco Phorum where Phine Phamily-Phriendly Pholks Phull of Philco Phacts and P...MrFixr55 — 08:41 AM

[-]
Who's Online
There are currently no members online.

>