Welcome Guest! Be sure you know and follow the Phorum Rules before posting. Thank you and Enjoy! (January 12, 2025) x

Thread Closed

Philco 640 - Need Some Help
#8

(06-30-2016, 10:06 AM)Steve Davis Wrote:  The very first thing to do is, touch the grid cap of the 85 tube with your finger. Do you get a loud hum? Next, place another radio next to the radio under test to see if you can tune the local oscillator of the nonworking radio.

Steve

This is the strategy that should be used with any dead radio - (1) Can you get some hum in the speaker by touching the grid of the last couple stages? Then your audio section is probably working.  Otherwise, concentrate on those last one or two stages.

If the audio is working, (2) determine if the LO oscillator is working.  If not, concentrate on the LO / converter stage.

If the LO is working, then why is the signal not passing through and reaching the audio stages of the radio? This is where you can get out your signal generator and start tracing a signal through, stage by stage.

Mark K8KZ


Messages In This Thread
Philco 640 - Need Some Help - by Geoff - 06-29-2016, 06:07 PM
RE: Philco 640 - Need Some Help - by Radioroslyn - 06-29-2016, 07:52 PM
RE: Philco 640 - Need Some Help - by Geoff - 06-29-2016, 08:05 PM
RE: Philco 640 - Need Some Help - by Geoff - 06-30-2016, 02:37 AM
RE: Philco 640 - Need Some Help - by Radioroslyn - 06-30-2016, 07:45 AM
RE: Philco 640 - Need Some Help - by Steve Davis - 06-30-2016, 10:06 AM
RE: Philco 640 - Need Some Help - by markmokris - 07-01-2016, 11:59 AM
RE: Philco 640 - Need Some Help - by Geoff - 07-01-2016, 04:00 PM
RE: Philco 640 - Need Some Help - by Geoff - 07-01-2016, 04:01 PM
RE: Philco 640 - Need Some Help - by Geoff - 07-01-2016, 04:02 PM
RE: Philco 640 - Need Some Help - by Geoff - 07-01-2016, 04:04 PM
RE: Philco 640 - Need Some Help - by Geoff - 07-01-2016, 04:10 PM
RE: Philco 640 - Need Some Help - by Geoff - 07-01-2016, 04:16 PM
RE: Philco 640 - Need Some Help - by Radioroslyn - 07-01-2016, 07:19 PM
RE: Philco 640 - Need Some Help - by Geoff - 07-01-2016, 07:20 PM
RE: Philco 640 - Need Some Help - by Radioroslyn - 07-01-2016, 08:19 PM
RE: Philco 640 - Need Some Help - by Geoff - 07-02-2016, 01:02 AM
RE: Philco 640 - Need Some Help - by Geoff - 08-04-2016, 06:39 PM
RE: Philco 640 - Need Some Help - by Geoff - 08-04-2016, 08:08 PM
Philco 640 Shadow Meter Bulb Type - by Geoff - 08-04-2016, 07:04 PM



Users browsing this thread: 1 Guest(s)
[-]
Recent Posts
54C Complete Teardown/Rebuild
Hello Roy, here is this one sincerely Richardradiorich — 12:45 AM
54C Complete Teardown/Rebuild
Richard, Had grabbed it already but thank you just the same.  I find myself wanting to find some way to block out the...glyphmon — 12:03 AM
54C Complete Teardown/Rebuild
Hello roy, here is a link to the schematic . Sincerely Richardradiorich — 11:54 PM
54C Complete Teardown/Rebuild
Richard, The Silvertone 2014 also is a transformerless set, so I am incorporating a 1:1 600 ohm audio isolation transfo...glyphmon — 11:37 PM
Preliminary work on wife's Silvertone 2014
Did an alignment today which was interesting.  IF alignment went great, almost all was already spot-on.  Adjusting on th...glyphmon — 11:35 PM
54C Complete Teardown/Rebuild
The main problem with adding a Bluetooth input is that this set lacks a traditional power transformer to isolate it from...radiorich — 11:19 PM
54C Cabinet Refinish
I started stripping this cabinet before it got super chilly out because I knew I wasn't going to be able to work on ...glyphmon — 11:18 PM
54C Complete Teardown/Rebuild
While I'm waiting to wrap up the final steps on my wife's Silvertone 2014, I started disassembly on the next project.  O...glyphmon — 11:07 PM
Preliminary work on wife's Silvertone 2014
Hello roy, that great news glad it worked out for you !! Sincerely Richardradiorich — 10:50 PM
Preliminary work on wife's Silvertone 2014
Safety caps arrived today.  Soldered one in and had a successful first power-up.  No magic smoke escaped and it tunes in...glyphmon — 09:53 PM

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

>