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

41-81 AVC Problem?
#4

I've been out of town, so I'm just getting back to this today.

The 250 mmf AVC filter capacitor tests good, so I didn't replace it.

As 7estatdef suggested, I measured the AVC voltage from the IF side of the 10 Meg AVC resistor (#13) to ground. With the radio tuned to the strongest local station, the voltage measured about 750 mv DC. On a weak station, it was about 330 mv DC. Tuned away from any station, it was still about 330 mv.

The measurements were similar with my VTVM and with my modern digital multimeter, which is rated at 10 Meg input resistance. The VTVM measured about 30 mv higher. It is rated 11 Meg/volt (1 Meg in probe), and I'm not too confident of the calibration.

I don't know how to interpret these measurements. Does this amount of difference seem reasonable?

Edited to add: I moved the cabinet around to reorient the loop antenna with respect to various radio stations. The AVC voltage when tuned to a strong station went up to 950 mv DC, but it was still around 330 mv on weak stations or between stations. The chassis was outside the cabinet, connected to the loop and ground with test leads. My workbench is in my basement, so it is likely that I'm getting weaker reception on all stations than if I were upstairs. I imagine the AVC voltage on strong stations would increase even more if I were upstairs.

Edited again: I tried an NOS 1H5GT detector tube without any change.

John Honeycutt


Messages In This Thread
41-81 AVC Problem? - by Raleigh - 06-07-2010, 12:09 AM
Re: 41-81 AVC Problem? - by codefox1 - 06-07-2010, 10:28 AM
Re: 41-81 AVC Problem? - by 7estatdef - 06-07-2010, 09:19 PM
Re: 41-81 AVC Problem? - by Raleigh - 06-18-2010, 02:02 PM
Re: 41-81 AVC Problem? - by rghines1 - 06-19-2010, 02:14 PM
Re: 41-81 AVC Problem? - by Chuck Schwark - 06-19-2010, 06:23 PM
Re: 41-81 AVC Problem? - by Raleigh - 06-21-2010, 09:52 AM



Users browsing this thread: 1 Guest(s)
[-]
Recent Posts
The list of my radio & TV collection!
Peter; I can't say for certain but many North American made radios from that era, the late 1940s onward, had silver m...Arran — 02:06 AM
Philco 39-7C Restore
A little more work today. I got the first IF transformer back together after replacing the wiring going to the 78 tube ...klondike98 — 12:06 AM
Two small radios from France. Restoration and review.
And here they are, the French beauties ready: In summary, the suspicion that radio transmits the national cha...Vlad95 — 10:46 PM
Two small radios from France. Restoration and review.
One is ready for washing, the other for painting: ATTENTION Faint-hearted and heart patients, please d...Vlad95 — 10:36 PM
Two small radios from France. Restoration and review.
Range Switch Block: I thought that mica capacitors of this type died out in the 30s, but no, they just moved ...Vlad95 — 10:29 PM
Two small radios from France. Restoration and review.
Chassis bottom view: Again, like twins, especially in the range switch part. Front panels: And...Vlad95 — 10:25 PM
Two small radios from France. Restoration and review.
Chassis removed, front view: Chassis rear view: It will be enough for the first device to prescribe a bath. Bu...Vlad95 — 10:11 PM
Two small radios from France. Restoration and review.
France Peculiarities of national character. Excelsior-52 threw me off track. It was too far outside my established...Vlad95 — 10:06 PM
Philco 16b no shortwave reception
First let thank everyone who helped ID this radio a few weeks ago! I have replaced all the capacitors and was able to r...Ken D. — 08:07 PM
Philco model 38 code 121 not receiving signal.
Ah yes, the Philco "Green Death" strikes again, someone suspected that cellulose nitrate based insulation migh...Arran — 06:23 PM

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

>