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
Philco model 38 code 121 not receiving signal.
Congrats on your success Stormlord. My rough guess is that since both the 15 and the 1A6 are supposed to be shielded, I...MrFixr55 — 10:04 PM
The list of my radio & TV collection!
A little light Saturday positive about our hobby in our feed... My new every Saturday video about antique radio equipme...RadioSvit — 02:12 PM
Model 70 Cabinet Trim
musar , Well if you have any more questions feel free to post away . Sincerely Richardradiorich — 08:56 PM
Model 70 Cabinet Trim
Although I have not made any cabinets or cabinet parts for a couple of years, I still have some parts left over, includi...Steve Davis — 06:26 PM
philcorepairbench.com - shadow-meter
Thanks Ron. But I can't find those articles.fenbach — 02:43 PM
Model 70 Cabinet Trim
Thank you, Gary. Before making my original post, I had clicked on "Steve Davis Cabinets" only to find that it...musar — 02:25 PM
philco predicta
Welcome to the Phorum, cgl18! I am not your resource for television repair, but lots of friendly help is available here...GarySP — 02:12 PM
Model 70 Cabinet Trim
Welcome to the Phorum, musar! You can send Steve Davis a private message (PM). The site is at the top of the Home page...GarySP — 02:09 PM
Model 70 Cabinet Trim
How do I contact him? The only contact information for him I could find when searching online was a telephone number th...musar — 10:38 AM
philco predicta
Hello, good afternoon, I would like to ask what the possible problem could be if I don't have an image on the screen. I ...cgl18 — 10:19 AM

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

>