CT-2 radio motorboating sound
Posts: 7
Threads: 1
Joined: Jan 2012
I have replaced all the caps including the filter caps, but none of the ceramic ones. I get a motorboating audio sound that has a frequency change with the changing of the volume control level. I can hear a faint station in the background. Has anyone had this problem with this chasis and can lead me in the right direction to fix the radio?
Jay :
Posts: 7,283
Threads: 268
Joined: Dec 2009
City: Roslyn Pa
Check 14. All connections should show a low resistance to ground. Like less than 30 ohms.
Terry
When my pals were reading comic books
I was down in the basement in my dad's
workshop. Perusing his Sam's Photofoacts
Vol 1-50 admiring the old set and trying to
figure out what all those squiggly meant.
Circa 1966
Now I think I've got!
Terry
Posts: 7
Threads: 1
Joined: Jan 2012
What is #14?
Jay :
Posts: 7
Threads: 1
Joined: Jan 2012
Has anyone got a set of voltage readings on various tubes in the CT-2 chassis. I hate the Ryder schematics. I suppose they were OK in the days long ago when everyone was working on these radios at least once week. They probably had voltge readings written down in a book. I am used to using Howard Sams schematics and service sheets. I am spoiled, I guess. Any help along this line will be appreciated.
Jay
Posts: 7,283
Threads: 268
Joined: Dec 2009
City: Roslyn Pa
It's on the Rider diagram #14 is the oscillator coil.
Terry
When my pals were reading comic books
I was down in the basement in my dad's
workshop. Perusing his Sam's Photofoacts
Vol 1-50 admiring the old set and trying to
figure out what all those squiggly meant.
Circa 1966
Now I think I've got!
Terry
Posts: 2,128
Threads: 18
Joined: Oct 2008
City: Merrick, Long Island, NY
Schematic here with plenty of voltage points. Bear in mind these were taken with meters of the day that somewhat loaded down the circuit, so you may get higher readings. Not much of a voltage divider tree here. So start here.
http://www.nostalgiaair.org/PagesByModel...014125.pdf
Posts: 7,283
Threads: 268
Joined: Dec 2009
City: Roslyn Pa
CF Wrong set his is a car radio CT-2 not the PT-2 table radio.
Terry
When my pals were reading comic books
I was down in the basement in my dad's
workshop. Perusing his Sam's Photofoacts
Vol 1-50 admiring the old set and trying to
figure out what all those squiggly meant.
Circa 1966
Now I think I've got!
Terry
Posts: 7
Threads: 1
Joined: Jan 2012
That reference brings up a Philco PT2 chassis with totally different tubes and a lot lower B+.
I would like to see voltages for the CT2 chassis if anyone has such.
I have 205 VDC at the first filter cap and 193V at the second filter cap. I guess that is normal for this chassis?
The rersistance to ground at 14 is less than 30 ohms at all 4 connections.
As I turn up the volume, the motorboating sound turns into a fairly smooth humming sound.
Posts: 7,283
Threads: 268
Joined: Dec 2009
City: Roslyn Pa
HV sounds OK. Starting at the rf amp tube with the set on start pulling the tubes in order mixer, IF amp... Until the motorboating stops. That will tell you which stage is the problem.
Terry
When my pals were reading comic books
I was down in the basement in my dad's
workshop. Perusing his Sam's Photofoacts
Vol 1-50 admiring the old set and trying to
figure out what all those squiggly meant.
Circa 1966
Now I think I've got!
Terry
Posts: 2,128
Threads: 18
Joined: Oct 2008
City: Merrick, Long Island, NY
7estatdef Wrote:CF Wrong set his is a car radio CT-2 not the PT-2 table radio.
Terry I need new glasses.
Posts: 160
Threads: 36
Joined: Jan 2006
PT- 2 is a 1935 Packard, I restored one once, These old Transitones had oscillator troubles sometime you can repair them by rewinding and finding the brake, but this sound like a power supply problem go though the work you did double check, a drop of soider in the wrong play can give you fits,I've done it!
Posts: 10
Threads: 0
Joined: Nov 2012
City: Fontana, Ca.
do you have the first filter cap hooked with nthe neg lead going to the pwr trans sec CT? these Philcos had the CT going to a choke and the other side of the winding was grounded to get nbias voltage for the audio tubes, the first filter had the neg lead going to the trans. CT and the second filter neg lead to ground, the filters were common pos.
Posts: 2,128
Threads: 18
Joined: Oct 2008
City: Merrick, Long Island, NY
I think you gents are onto something. Often the chassis is not the most negative point in the voltage divider, and there is a filter capacitor that has it's positive leg to the chassis, and negative side to the center tap of the power transformer. Get this wrong, and the set will not work. Either that or you are operating the radio in a marina.
Posts: 62
Threads: 8
Joined: Oct 2012
City: Hidden Valley, AZ
Ha!
DG
Pacing the cage...
Users browsing this thread: 1 Guest(s)
|
Recent Posts
|
Jackson 715 not working
|
Mrfixr55, its working now. I cleaned the switches and sockets with spray cleaner. Thanks for helping on this one.daveone23 — 06:26 PM |
Jackson 715 not working
|
Now that you posted the schematic, I don't know why that Sprague electrolytic cap is across the meter, as it is not indi...MrFixr55 — 05:51 PM |
HiFi (Chifi) tube amp build - but my own design.
|
What may be lacking in the PP Tube amps may be the 2nd harmonics, which some, especially RCA back in the day called &quo...MrFixr55 — 05:32 PM |
Jackson 715 not working
|
Usually in an emission tester, the tube under test is measured as if it were a diode. So, some testers connect all the g...RodB — 04:17 PM |
Restoring Philco 37-604C
|
Yep. F5 is green, D5 is Red.
Red is Bad.
Green is Clean.morzh — 01:30 PM |
Jackson 715 not working
|
I did start to do that but I stalled out because I could not figure out how the grid and plate get voltage. In this diag...daveone23 — 11:52 AM |
Restoring Philco 37-604C
|
(Insert Homer Simpson "DOPF" Here.)
When all fails, look at the can. Took the Ron Ramirez advice, red Caig D...MrFixr55 — 09:23 AM |
Philco 91 Speaker Replacement
|
From your text I am not sure if you intend to use the existing speaker with a resistor instead of the field coil.
It wo...morzh — 08:44 AM |
Philco 91 Speaker Replacement
|
My field coil is bad. I am still hoping to find an original, but if I can't I will go with a fitting Philco speaker, 125...dconant — 08:34 AM |
Philco 91 Speaker Replacement
|
As Rod said, it is OK to use a fitting speaker, and then look for an original one.
If you buy a Hammond 125 output tr...morzh — 08:15 AM |
Who's Online
|
There are currently 3952 online users. [Complete List] » 1 Member(s) | 3951 Guest(s)
|
|
|
|