It's been a while... FOUND
Posts: 825
Threads: 113
Joined: Aug 2012
City: The Villages
State, Province, Country: Florida
Since I've run across a problem like this. I have a 49-905 that I just finished replacing all the electrolytic and paper capacitors. All tubes and resistors check ok. My problem is a hum. It gets louder with the volume control but never over powers a station. I checked all the wires and they appear to be dressed as original. Even though the tubes tested good I swapped them out 1 by 1 with no difference.
Any help will be appreciated.
Schematic
Thanks,
Eric
The Villages, FL
Member: Philco Phorum, ARF, ARCI & Radiomuseum.org
(This post was last modified: 10-03-2015, 04:04 PM by Eric Adams.
Edit Reason: spelling
)
Posts: 15,527
Threads: 545
Joined: Oct 2011
City: Jackson, NJ
Eric
Hum can be anything.
Does it change with tuning or stays constant?
Now, often it is a result of bad ground. Look at rivets holding ground leaves where wire solder to. These are often the culprits.
People who do not drink, do not smoke, do not eat red meat will one day feel really stupid lying there and dying from nothing.
Posts: 825
Threads: 113
Joined: Aug 2012
City: The Villages
State, Province, Country: Florida
It stays constant, but it doesn't drown out a station when I tune it in. It kind of stays in the background.
One more thing I forgot to mention. When I first got it completed, there was no hum. I aligned both AM and FM without a sound. I put it in the cabinet and played it for about 15 or 20 minutes and then it started. Does that help?
Eric
The Villages, FL
Member: Philco Phorum, ARF, ARCI & Radiomuseum.org
Posts: 7,273
Threads: 268
Joined: Dec 2009
City: Roslyn Pa
Hey Eric,
I'd try swapping the tubes you may have gotten a cathode to control grid short internally in the tube. Higher voltage heater tubes are a little more suspect than others. As Mike said check grounds is good too.
Terry
Posts: 825
Threads: 113
Joined: Aug 2012
City: The Villages
State, Province, Country: Florida
Thanks, Terry. Tube swap has been tried. I'm just going to check all the grounds and recheck all of my solder joints.
I'll let you guys know how it turns out.
Thanks,
Eric
The Villages, FL
Member: Philco Phorum, ARF, ARCI & Radiomuseum.org
Posts: 825
Threads: 113
Joined: Aug 2012
City: The Villages
State, Province, Country: Florida
Well, I took it off of the punishment shelf for another look. I tried tube swaps again. It was the 19C8! I replaced it and the hum was completely gone.
Thanks for your help everyone.
Eric
The Villages, FL
Member: Philco Phorum, ARF, ARCI & Radiomuseum.org
Posts: 1,562
Threads: 56
Joined: Nov 2008
City: Sedona, AZ/Placentia/CA
Congrats Eric, one more off the punishment shelf.
Jerry
A friend in need is a pest! Bill Slee ca 1970.
Posts: 5,071
Threads: 269
Joined: Nov 2012
City: Bandon
State, Province, Country: OR
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 3468 online users. [Complete List] » 1 Member(s) | 3467 Guest(s)
|
|
|
|