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

Thread Closed

1936 Philco 645
#27

Let me first apologize for misstating my shadowmeter issue. The vane remains slightly deflected with MAXIMUM signal. I can bend the light bracket to center the shadow, and the shadow will narrow substantially with tuning-- it just won't be at minimum width unless the vane centers perfectly when tuned accurately.

I was going to illustrate that with photos, but unfortunately the radio went tango uniform last night (any Air Force folks out there?). No audio--no apparent signal.

Nevertheless, here's a 20-second video of the shadowmeter. Power starts when the light comes on, the vane deflects maximum left and then returns slightly towards center. The vane remains in the position it is when the video stops. This is with no shunt, no antenna, and no apparent signal. I think this is normal.

https://picasaweb.google.com/coldrb/Febr...directlink

Now, to get the radio working again. While doing nothing but turning the tuner knob, the radio went silent. Nothing but a slight hum out of the speaker. No evidence of any signal received or amplified.

I have only a rudimentary understanding of electronics, but I did my best to diagnose until 2 a.m. The only anomaly I have found is the 6A7 oscillator/detector shows zero voltage at the oscillator grid. All other tube socket and power transformer voltages are the same as before the set died

I have double-tested the 6A7 with both transconductance and emissions tester; verified the appropriate continuity through the input transformer, output transformer, oscillator transformer; and randomly tested a number of other components. As you can see, I'm now flailing aimlessly at the problem and need some direction.

So, given the sudden failure and zero oscillator grid voltage (It was -22 V), can someone give me some direction in diagnosing the problem?

I have a legible schematic posted here:

https://picasaweb.google.com/lh/photo/gv...directlink

Grateful for Guidance,
Winky


Messages In This Thread
1936 Philco 645 - by Ronin61 - 03-23-2013, 10:33 PM
RE: 1936 Philco 645 - by morzh - 03-23-2013, 11:48 PM
RE: 1936 Philco 645 - by 7estatdef - 03-24-2013, 08:58 AM
RE: 1936 Philco 645 - by Ronin61 - 03-24-2013, 11:05 AM
RE: 1936 Philco 645 - by Ronin61 - 03-24-2013, 02:21 PM
RE: 1936 Philco 645 - by Ronin61 - 03-24-2013, 02:38 PM
RE: 1936 Philco 645 - by Ronin61 - 03-24-2013, 02:39 PM
RE: 1936 Philco 645 - by Ronin61 - 03-24-2013, 02:41 PM
RE: 1936 Philco 645 - by 7estatdef - 03-24-2013, 04:06 PM
RE: 1936 Philco 645 - by Ronin61 - 03-26-2013, 04:13 PM
RE: 1936 Philco 645 - by 7estatdef - 03-27-2013, 08:38 AM
RE: 1936 Philco 645 - by morzh - 03-27-2013, 12:15 PM
RE: 1936 Philco 645 - by codefox1 - 03-28-2013, 04:34 AM
RE: 1936 Philco 645 - by Ronin61 - 04-07-2013, 09:30 PM
RE: 1936 Philco 645 - by 7estatdef - 04-10-2013, 06:27 PM
RE: 1936 Philco 645 - by Ronin61 - 04-11-2013, 04:58 PM
RE: 1936 Philco 645 - by Ronin61 - 04-22-2013, 10:57 AM
RE: 1936 Philco 645 - by 7estatdef - 04-22-2013, 05:13 PM
RE: 1936 Philco 645 - by Winky Dink - 02-02-2014, 05:57 PM
RE: 1936 Philco 645 - by Mondial - 02-02-2014, 06:15 PM
RE: 1936 Philco 645 - by Winky Dink - 02-02-2014, 06:32 PM
RE: 1936 Philco 645 - by Winky Dink - 02-02-2014, 11:20 PM
RE: 1936 Philco 645 - by Mondial - 02-03-2014, 01:07 AM
RE: 1936 Philco 645 - by Winky Dink - 02-03-2014, 03:43 AM
RE: 1936 Philco 645 - by Mondial - 02-03-2014, 09:24 AM
RE: 1936 Philco 645 - by Ron Ramirez - 02-03-2014, 11:27 AM
RE: 1936 Philco 645 - by Winky Dink - 02-03-2014, 07:35 PM
RE: 1936 Philco 645 - by Winky Dink - 02-04-2014, 01:00 AM
RE: 1936 Philco 645 - by Winky Dink - 03-24-2014, 10:10 AM
RE: 1936 Philco 645 - by codefox1 - 03-24-2014, 10:52 AM
RE: 1936 Philco 645 - by Winky Dink - 03-24-2014, 11:41 AM



Users browsing this thread: 1 Guest(s)
[-]
Recent Posts
HiFi (Chifi) tube amp build - but my own design.
It's the other forum. I'm also in DIY, but mostly read there. Honestly, I kinda jumped into this without much thought to...TV MAN — 10:43 AM
Philco 71 Code 125
Hello,  I am in need of a schematic for this radio. Mine has the three separate circular tube shields and a shadow me...dconant — 08:06 AM
Stromberg Carlson 1500 Squeal
And life just keeps getting more complicated.dconant — 07:57 AM
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

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

>