This radio doesn't know the words!
Posts: 825
Threads: 113
Joined: Aug 2012
City: The Villages
State, Province, Country: Florida
Because at low volume it hums
The latest subject is a DeWald C-800 . With the volume turned all the way down, I have a steady hum. It doesn't get any louder when the volume is turned up. It just hangs back in the background when tuned into a station.
All caps replaced (except micas). Resistors checked and replaced as necessary. All tubes tested ok. Alignment done. On both AM and FM stations come in loud and clear.
Any ideas? This has really got me . I may take a ride over to freezing lake Michigan and jump in-like someone else we know
Thanks,
Eric
The Villages, FL
Member: Philco Phorum, ARF, ARCI & Radiomuseum.org
Posts: 15,704
Threads: 551
Joined: Oct 2011
City: Jackson, NJ
Eric
There have been several threads lately addressing the similar problem.
All I can tell you:
1. Check all tubes for shorted Filament and Cathode (uually output ad Det/1st Audio)
2. Bad grounding - rivets etc
3. Shorted Gnd to chassis if separate, or shorted Filament wire to chassis.
4. Mechanical noise from the power transformer
You have to poke around.
Like, pull tubes one by one, see if it stops and with what tube. Then go from there.
Posts: 7,283
Threads: 268
Joined: Dec 2009
City: Roslyn Pa
Agree with Mike but when you start pulling tubes leave the rectifier in. If you pull it you will loose all HV Also replace the tube back into it's socket before going to the next one. You don't want to have with just the rectifier tube in it at the end of testing.
Terry
Posts: 15,704
Threads: 551
Joined: Oct 2011
City: Jackson, NJ
Yep, that's the point - one at a time while having the HV, we need to know which one it stops at.
Posts: 825
Threads: 113
Joined: Aug 2012
City: The Villages
State, Province, Country: Florida
Thanks for the ideas, guys. I don't think that I should pull tubes because it has no power transformer. I have swapped out each tube one by one with no change. I'll check grounds. Anything else you can think of for this AC/DC beauty?
Eric
The Villages, FL
Member: Philco Phorum, ARF, ARCI & Radiomuseum.org
Posts: 15,704
Threads: 551
Joined: Oct 2011
City: Jackson, NJ
Posts: 825
Threads: 113
Joined: Aug 2012
City: The Villages
State, Province, Country: Florida
Nope. has polarized plug - common to ground.
Eric
The Villages, FL
Member: Philco Phorum, ARF, ARCI & Radiomuseum.org
Posts: 2,128
Threads: 18
Joined: Oct 2008
City: Merrick, Long Island, NY
Don't bet your life or your reception on wall socket being wired correctly. Try in another room where a similar set works OK.
Posts: 15,704
Threads: 551
Joined: Oct 2011
City: Jackson, NJ
Although I try to wire chassis following Wide-Neutral convention. I would never rely on it for safety. For exactly the same reason - it cannot be guaranteed.
Posts: 4,686
Threads: 51
Joined: Sep 2008
City: Sandwick, BC, CA
I would loose the polarized plug, at least temporarily, I see that this is an AM/FM set so I would go back to how the factory had it wired until you can rule that out. Some AC/DC sets do not like having the neutral and hot side swapped on the power switch since it's often on the back of the volume control, I also noticed that the FM and AM detector tubes have their heaters connected closest to common negative/AC Neutral at the end of the filament string. If it is not being caused by this, or a heater to cathode short, then there must be an open ground connection, or something incorrectly wired.
Regards
Arran
Users browsing this thread:
|
Recent Posts
|
Philco 91 Speaker Replacement
|
The spider is glued on the cone and so is the voice coil. I think you can use a cotton swab dipped in acetone and carefu...RodB — 02:42 PM |
Restoring Philco 37-604C
|
Yes I saw that. If I knew, I'd probably try to arrange for getting it myself. But I have just got one.
Which does not m...morzh — 01:44 PM |
Philco 38-2 Automatic Tuning
|
When you push the lever, you are supposed to rotate the disk to the desired station.
Then the magnetic tuning will acqu...morzh — 01:42 PM |
Philco 38-2 Automatic Tuning
|
I figure out the muting from another picture that helped. Now I need to know how the automatic tuning works. When I push...dconant — 12:11 PM |
Philco 91 Speaker Replacement
|
How would I go about removing the spider from the cone?dconant — 12:04 PM |
Philco 38-2 Automatic Tuning
|
Hello, I am having trouble getting my automatic tuning to stay unmuted. If I play with the tuning handle I can get it to...dconant — 10:51 AM |
Does anyone make photofinish replacements?
|
Here’s the link to the DIY photofinish section of our site:
klondike98 — 09:46 AM |
Delco car radio Peko vibrator converstion issues
|
Hi Richard,
Thx for posting the schematic. As I remember as a kid, these were great performers for the time, likely...MrFixr55 — 08:56 AM |
Delco car radio Peko vibrator converstion issues
|
hello mr Fixr,
The Electro Powersupply that I am powering the radio with has a huge choke plus a 10,000ufd electrolyti...radiorich — 10:58 PM |
Delco car radio Peko vibrator converstion issues
|
How about putting a choke in the power supply?
The big cap was likely an attempt to stabilize the DC. Kids who cre...MrFixr55 — 09:19 PM |
Who's Online
|
There are currently no members online. |
|
|