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

48-475 signal injection
#1

Hi all! Back again!

This time, I've got a 48-475. Replaced all the caps (left most of the mica), checked wiring, replaced resistors if out of tolerance. Got a hum that varies with volume, but not too concerned with that as it will probably go away once I figure out this problem.

I inject an audio signal on pin 3 of the 7C6 ("D" of section 2) and get a good, loud output from the speaker. But when I inject the same signal on pin 6 of the output tube ("B" of section 2), I get no audio. All it does is silence the hum. Tube checks out O.K., but someone did replace it (should be a 7B5) with a 7C5.

Looks like the 7C5 should work in  place of the 7B5.

Voltages everywhere check out O.K., albeit about 20V low.

I've spent waaaaaaaay too much time on this radio already, since it had extensive repair in the past. But I did trace down all the wiring, and everything looks O.K. The only componet that was NOT in the radio was R312 (6.8Meg), but that goes to WS-2® which should only affect FM.

This is only half the schematic. I'll upload the other half if needed.

[Image: http://i1367.photobucket.com/albums/r796...ccckac.jpg]

Ideas anyone?

Thanks,

Pat


Messages In This Thread
48-475 signal injection - by Patrick - 09-27-2015, 02:34 PM
RE: 48-475 signal injection - by Patrick - 09-29-2015, 02:47 PM
RE: 48-475 signal injection - by Radioroslyn - 09-29-2015, 06:11 PM
RE: 48-475 signal injection - by Patrick - 09-29-2015, 06:41 PM
RE: 48-475 signal injection - by Raleigh - 09-29-2015, 07:53 PM
RE: 48-475 signal injection - by Patrick - 09-29-2015, 08:54 PM
RE: 48-475 signal injection - by Raleigh - 10-02-2015, 10:27 PM
RE: 48-475 signal injection - by Patrick - 10-04-2015, 01:00 AM
RE: 48-475 signal injection - by Patrick - 10-09-2015, 02:44 PM
RE: 48-475 signal injection - by Patrick - 10-09-2015, 01:23 PM



Users browsing this thread: 1 Guest(s)
[-]
Recent Posts
462ron
Hi Levi, here’s just a thought. Most radios run the oscillator higher than the dial setting. Say you set your radio to 1...462ron — 10:10 AM
1930s Stewart-Warner Tombstone Radio need help identifying model number
Another Update: I found a couple of damaged coils inside this radio that might have something to do with why this radio ...captainclock1988 — 10:51 PM
6TPZ and 5TPO Radio Help
If you are still on 5TPO, you lost me there. What X7? What Points 1 and 2?morzh — 08:37 PM
6TPZ and 5TPO Radio Help
Quick progress report: X7 is broken. Only one leg soldered, the other missing and the diode is cracked. I've replaced...R3Sons — 05:05 PM
6TPZ and 5TPO Radio Help
Oh...and you have electrolytic caps there. All need to go and be replaced.morzh — 04:36 PM
6TPZ and 5TPO Radio Help
Thanks, will do.R3Sons — 01:25 PM
1930s Stewart-Warner Tombstone Radio need help identifying model number
UPDATE: I was able to pick up a signal generator on the cheap (amazingly enough) on feebay and I did an IF alignment fol...captainclock1988 — 09:53 AM
Philco 91 Schematic
Hi Rod, The resistor connects to pin 4 and the ungrounded side of block 9. From pin 9 of the RF tube to one side of ...dconant — 09:34 AM
Just got a 49-1613 need to know...everything!
I just found your post. I have this exact same model, and have had it since 1985 when I was 15 years old! I performed a ...MuzzcoVW — 09:11 AM
B&K 1077B no video
Hello Tim, I would if it's a leaky Capacitor So are all 3 of those B- voltages low then ? Sincerely Richardradiorich — 01:55 AM

[-]
Who's Online
There are currently 4498 online users. [Complete List]
» 2 Member(s) | 4496 Guest(s)
AvatarAvatar

>