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

Thread Closed

A short in that old Philco 77
#1

http://www.nostalgiaair.org/pagesbymodel...013838.pdf

I finally have gotten serious about that Philco 77 (busy Summer what with trips to take and somehow four other radios got in line before it), but after restuffing the bakelite boxes and the small metal cap boxes and the large cap box, recapping the tone control, AND replacing all of the resistors with 1 watt new ones, it failed a dim bulb test.

Measuring the resistance on the power transformer, I find low resistance on the primary (about 20 or a bit more-going on memory here), VERY low resistance (0.1-0.2 ohms) on the filament secondary for the 80 (10 & 11), and on the ones for the 45s (7 & 8) and 24As & 27 (5 & 6). Under 300 ohms on the HV winding (9 & 12).

The wire-wound resistors measure as they should, and I've triple-checked the large cap box hook-up. The choke and the output transformer and the field coil all measure as they should.

I guess my question is: Should I be seeing higher numbers on the various filament windings, or are these numbers about right, AND if these numbers are about right, I should be looking for a short further down the line, right?

I have yet to try powering it up with no tubes, but I guess that is next?

UPDATE: when I tried bringing the transformer up with no tubes in it and a dim bulb (15 watts) in series with my variac, I bee a faints glow around 70 volts and a soft glow at 110 volts. I guess that qualifies as a shorted transformer?

Charlie in San Antonio


Messages In This Thread
A short in that old Philco 77 - by ccomer1955 - 08-12-2015, 07:34 PM
RE: A short in that old Philco 77 - by ccomer1955 - 08-12-2015, 09:33 PM
RE: A short in that old Philco 77 - by ccomer1955 - 08-13-2015, 11:41 AM



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 1987 online users. [Complete List]
» 1 Member(s) | 1986 Guest(s)
Avatar

>