Philco 71B Code 125 speaker thumping
Posts: 44
Threads: 8
Joined: Feb 2021
City: Durham
State, Province, Country: NC
Bought this set on eBay. I replaced the electrolytics and safety capacitors and the set plays but has a rhythmic "heartbeat" sound thumping from the speaker.
I am getting stations but is interrupted by the regular thumping sounds. Sounds to be around 60 per minute. It does not look like anyone has reworked the Bakelites so before I do that I wanted to see if anyone else has seen this before.
Posts: 18,427
Threads: 622
Joined: Oct 2011
City: Jackson
State, Province, Country: NJ
I wonder if you have an electronic clock with a step motor nearby.
Doesn't look like anything inside would make it.
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: 44
Threads: 8
Joined: Feb 2021
City: Durham
State, Province, Country: NC
I do have an electronic clock and speaker connected to a nearby PC. I disconnected from the wall outlet and the thump continues.
I have attached a movie capture for review.
Thank you for your response
Posts: 18,427
Threads: 622
Joined: Oct 2011
City: Jackson
State, Province, Country: NJ
You cannot attach movie here. It's not attached.
Put it on some videohosting and give the link.
PS. Actually, a good idea to check that whatever you attached is actually attached.
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: 2,327
Threads: 23
Joined: Jul 2020
City: Greenlawn
State, Province, Country: NY
HI DM Blackburn,
This sounds like a a capacitor problem. First off, it is important to note that the 2 main filter caps do not ground to the chassis, they connect to the center tap of the HV secondary. Make sure that the The "can" of the capacitors must be insulated from the chassis. The second possibility is dress of the grid cap for the First Audio stage (labeled Detector - Audio on the schematic. Make sure the lead is dressed correctly. If there is supposed to be a shield on this tube, ensure that it is in place. touch the wire. Does the "beat" change?
Next, "divide and conquer"
Does the "beat" noise occur with the volume control all the way down? If yes, the problem is in the audio stage or power suppl. If no, the next step is to power down and pull the detector tube. Power back up and raise the volume control. You may hear a little hum, but you should not hear the beat.
If no hum, power down, reinstall the detector tube and pull the IF tube. If no hum, reinstall the IF but leave the grid cap off. Repeat the test. If no hum, repeat the same procedure with the First detector. If no hum, repeat with the 1st RF Amp tube. This should help you isolate the stage that is causing the issue. The issue may be a bad capacitor, bad resistor, gassy tube, etc.
If the Bakelite condenser blocks have not been serviced, do so. Remember, you can't just "bridge" the caps with new ones, the old ones must be take out of the circuit. Remember, some of these blocks have 2 caps or a cap and esistor inside. Several of these condensers are "B+ Bypass" condensers. Failure of these condensers can cause this problem. Service the "Filter Condenser Block" by replacing their components also. Check the continuity of the voltage divider resistors
Mike (Morzh) has written a great article on servicing theses Bakelite blocks without having to detach / reattach the lead wires. See the attached link:
https://philcoradio.com/library/index.ph...soldering/
Hope this helps
"Do Justly, love Mercy and walk humbly with your God"- Micah 6:8
"Let us begin to do good"- St. Francis
Best Regards,
MrFixr55
Posts: 1,797
Threads: 55
Joined: Feb 2015
City: Roseville, MN
Is it a putt-putt sound like an old motor boat or an intermittent buzz pulse like an electric fence? Try to see if you can control it with volume or antenna signal strength. We need to narrow it down to feedback or anything picked up on the antenna.
Posts: 18,427
Threads: 622
Joined: Oct 2011
City: Jackson
State, Province, Country: NJ
...and if we could listen to the sound (video or just audio file), it would help.
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: 44
Threads: 8
Joined: Feb 2021
City: Durham
State, Province, Country: NC
Can you tell me which video hosting app you use to save the video and create the link ?
Posts: 44
Threads: 8
Joined: Feb 2021
City: Durham
State, Province, Country: NC
Try this link to view a video of the thumping noise. I'm new at this so I hope this link works
https://studio.youtube.com/channel/UCZR7...DING%22%7D
Posts: 44
Threads: 8
Joined: Feb 2021
City: Durham
State, Province, Country: NC
Try this link to view a video of the thumping noise. I'm new at this so I hope this link works
https://studio.youtube.com/channel/UCZR7...DING%22%7D
Posts: 18,427
Threads: 622
Joined: Oct 2011
City: Jackson
State, Province, Country: NJ
Youtube is good.
And if you make the video public, we won't have to sign in to view it.
PS. And after I jumped through some hoops to sign in from work, it said i have no permission to view it.
Just go to the studio and make the video public.
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: 44
Threads: 8
Joined: Feb 2021
City: Durham
State, Province, Country: NC
I checked YouTube "Your videos" and the short is designated as Public with no restrictions
Posts: 18,427
Threads: 622
Joined: Oct 2011
City: Jackson
State, Province, Country: NJ
Then you should give us the link to the public version. You probably gave us the link you view yourself when you are in your account.
What is the name of it (exact)? We then could find it by name.
Or log out from the account, find it and give us the link to it then.
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: 44
Threads: 8
Joined: Feb 2021
City: Durham
State, Province, Country: NC
I signed out of my YouTube account and did a search for "Philco 71B Code 125 speaker thumping" and could play the video short.
My YouTube account is listed as Daryl Blackburn @darylblackburn52
Hopefully, this will work for you. Again, sorry, I'm new at this. Thanks for staying with me on this
Posts: 18,427
Threads: 622
Joined: Oct 2011
City: Jackson
State, Province, Country: NJ
Yep. It worked.
I think, yes, your radio is doing this.
Something drives the output to saturation maybe. It is a pretty sound hard click.
Does not look like motorboating.
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.
Users browsing this thread: 1 Guest(s)
|
|
Recent Posts
|
|
Philco P45-6365 Universal Transformer Instruction Manual
|
| Can anyone guide me to where this may be found?GRG — 03:00 PM |
|
54C Complete Teardown/Rebuild
|
| I don't think that I have encountered a 12Z3 before, curious how it uses one of those but includes a #43, which is a 25 ...Arran — 02:17 PM |
|
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 |
|
Who's Online
|
There are currently 2666 online users. [Complete List]
» 2 Member(s) | 2664 Guest(s)
|
|
|
|
 
|
![[-]](https://philcoradio.com/phorum/images/bootbb/collapse.png "[-]")
