Posts: 44
Threads: 9
Joined: Apr 2011
City: Pittsburgh, PA
Still new at this and new to Philco and superhets. Is it necessary to pull the coils out to test them? I haven't found a definitive answer in my research. Is there a cheat sheat available showing point to point testing that would verify continuity in all the coils w/o disturbing them. Thanks in advance. One curious thing I found was a single 16 mfd ecap instead of the 2 8mfds...probably a repair??? No stations as yet and I replaced the 16 mfd with a 22 mfd.
Posts: 7,273
Threads: 268
Joined: Dec 2009
City: Roslyn Pa
Most of the time the primary of the antenna coil and the feedback winding of the oscillator coil are the one that are commonly open.
Terry
(This post was last modified: 02-27-2012, 08:57 PM by Radioroslyn.)
Posts: 44
Threads: 9
Joined: Apr 2011
City: Pittsburgh, PA
(02-27-2012, 08:56 PM)7estatdef Wrote: Most of the time the primary of the antenna coil and the feedback winding of the oscillator coil are the one that are commonly open.
Terry
The only sound I get is steady soft hum and a noise like somebody is hitting radio with a rope at a steady cadence...curious.
Posts: 7,273
Threads: 268
Joined: Dec 2009
City: Roslyn Pa
Go a head and replace the paper caps, electrolytic caps and out of spec resistors. Then we can talk about coils.
Terry
Posts: 44
Threads: 9
Joined: Apr 2011
City: Pittsburgh, PA
After recapping the bakelites and rewinding the primary of the osc coil...still nothing in terms of reception. Primary of osc coil now measures 2.1 ohms vs. 3.4 of schematic. Antenna on grid cap of 6A7...still nothing. The .7 SW of antenna coil measures open. Would that knock out even BC reception??
Posts: 2,128
Threads: 18
Joined: Oct 2008
City: Merrick, Long Island, NY
(03-19-2012, 08:39 AM)sjhs1962 Wrote: After recapping the bakelites and rewinding the primary of the osc coil...still nothing in terms of reception. Primary of osc coil now measures 2.1 ohms vs. 3.4 of schematic. Antenna on grid cap of 6A7...still nothing. The .7 SW of antenna coil measures open. Would that knock out even BC reception??
It is customary to post link to schematic with question
http://www.nostalgiaair.org/PagesByModel...013793.pdf
If the antenna coil is open, it needs to be rewound or replaced. That being said and if voltages are reasonable, work backwards from the speaker (right to left) with a modulated signal generator to find out where you are losing signal.
Posts: 7,273
Threads: 268
Joined: Dec 2009
City: Roslyn Pa
If the primary of the ant coil as open you can hook the ant to the grid cap of the mixer tube and you should be able to receive radio signals. Is you local oscillator working?
Terry
Posts: 44
Threads: 9
Joined: Apr 2011
City: Pittsburgh, PA
(03-19-2012, 04:33 PM)7estatdef Wrote: If the primary of the ant coil as open you can hook the ant to the grid cap of the mixer tube and you should be able to receive radio signals. Is you local oscillator working?
Terry
http://www.philcoradio.com/tech/60evol.htm
No, oscillator not working. In addition plate voltages are high 370 vdc. Also, resistor on band switch measures 11 ohms ...schematic says 10k, but I have another 60 in a different version that works and this resistor also measures 11 ohms. Confused. Antenna on grid cap of 6A7 doesn't bring in anything.
(This post was last modified: 03-19-2012, 08:52 PM by sjhs1962.)
Posts: 15,527
Threads: 545
Joined: Oct 2011
City: Jackson, NJ
Your resistor measures 11 Ohm because it is in parallel to the antenna coil that actually says "11 Ohm" on it.
You know how paralleling resistors work, right?
(This post was last modified: 03-19-2012, 09:15 PM by morzh.)
Posts: 44
Threads: 9
Joined: Apr 2011
City: Pittsburgh, PA
(03-19-2012, 09:14 PM)morzh Wrote: Your resistor measures 11 Ohm because it is in parallel to the antenna coil that actually says "11 Ohm" on it.
You know how paralleling resistors work, right?
Thanks...tricky concept that could trip you up easily. I found the calculator online...of course you have to know that the resistors are in parallel.
Posts: 1,703
Threads: 55
Joined: Sep 2005
City: Evanston, IL
(03-19-2012, 09:44 PM)sjhs1962 Wrote: ...of course you have to know that the resistors are in parallel.
That's where experience in reading and interpreting a schematic helps with these kinds of issues.
Continued good luck,
Chuck
Posts: 7,273
Threads: 268
Joined: Dec 2009
City: Roslyn Pa
Well The thing isn't gonna work if the oscillator isn't running. Check the voltage on grid 2 of the 6A7. Should be pretty high like 100 volts. If not rewind oscillator feedback winding.
Terry
(This post was last modified: 03-21-2012, 06:21 PM by Radioroslyn.)
Posts: 13,776
Threads: 580
Joined: Sep 2005
City: Ferdinand
State, Province, Country: Indiana
And make sure that oscillator feedback winding is wound counterclockwise!
--
Ron Ramirez
Ferdinand IN
Posts: 44
Threads: 9
Joined: Apr 2011
City: Pittsburgh, PA
Osc coil wire that doesn't go to any terminals on actual osc coi....what is purpose of this coil wire? Does it go to cathode of 6A7?
Posts: 44
Threads: 9
Joined: Apr 2011
City: Pittsburgh, PA
On the antena coil, the primary is the inserted coil inside the tube and the secondary has the three taps. I am wondering if it is necessary to rewind the .7 sw coil since it doesn't function for the most part?
Users browsing this thread: 1 Guest(s)
|
Recent Posts
|
Correct model 84 Ac plug an cord type
|
From what I read Philco went to using brown rubber power cords in 1936, so cloth was used in the 1935 and earlier models...Arran — 11:25 PM |
Correct model 84 Ac plug an cord type
|
Hi Bruce,
I have not worked on an 84, but in general, power cords for almost any radio prior to 1938 was cloth covered...MrFixr55 — 08:34 PM |
Restoring Philco 38-14
|
OK, well, so after staring at the sch again, I realized the problem had to be the #12/12A padder.
I put a scope on the o...morzh — 08:15 PM |
Correct model 84 Ac plug an cord type
|
Hello Bruce,
I mostly use brown far as my cloth powercords go !
Here is the plug that I have used bakelite Acorn style...radiorich — 08:05 PM |
Correct model 84 Ac plug an cord type
|
Looking for as correct as can find the right Ac plug an the correct colored cloth line. Ive seen many old photos but mos...Bruce — 04:13 PM |
Restoring Philco 38-14
|
Rod
Two Y-caps make sense if you use them from L/N to the chassis; this is only makes sense in the transformer radios...morzh — 10:11 AM |
Restoring Philco 38-14
|
Mike, I'm curious about a specific use of he Y cap. Lately I've seen a single cap across the power transformer primary. ...RodB — 09:01 AM |
Restoring Philco 38-14
|
hello morzh ,
That sounds like a plan !
Sincerely Richardradiorich — 07:45 AM |
Restoring Philco 38-14
|
Richard,
It helped some, but I still had the whining when engaging the rear power strip (I did not realize it was fro...morzh — 07:07 AM |
Restoring Philco 38-14
|
Hello morzh,
Yes , that dreaded hum in my room where i do alighment I have my cable modem and router plus desktop plus ...radiorich — 11:25 PM |
Who's Online
|
There are currently 4501 online users. [Complete List] » 2 Member(s) | 4499 Guest(s)
|
|
|
|