Posts: 663
Threads: 142
Joined: Jun 2011
City: Elko,MN.
Have this thing re-capped now and it does play.
I don,t seem to have the volume I would like,and if you turn it up to about 1/2 volume it starts getting distorted and the volume does not really go up.
Someone replaced the volume switch with a combe on/off/volume switch due to a bad switch on the off pushbutton.
I wonder if the switch is under-rated for that chassis,or if there could be something else I should be looking at like maybe a tube?
This one has been a bear for a newbie like me to work on.
Any idea's?
Thanks again,
murf
Posts: 190
Threads: 8
Joined: Oct 2005
City: Lexington, SC
You picked a difficult set to start out. As far as distortion, I would make basic voltage checks in the audio section with emphasis on the audio output bias. Should be about -20V on the control grids of the 7C5s. Also make voltage readings on the other tubes in the radio too. Often problems can be found this way without elaborate test equipment. If basic voltage checks are good then alignment will have to be considered.
Concerns about a under-rated switch is misplaced. Tubes are usually Ok. These being locktal tubes there is concerned about pin connection issues. Rocking the tubes in the sockets can reveal a intermittent pin while listening to the radio.
http://www.nostalgiaair.org/Resources/497/M0013497.htm
Posts: 663
Threads: 142
Joined: Jun 2011
City: Elko,MN.
rghines1 Wrote:You picked a difficult set to start out. As far as distortion, I would make basic voltage checks in the audio section with emphasis on the audio output bias. Should be about -20V on the control grids of the 7C5s. Also make voltage readings on the other tubes in the radio too. Often problems can be found this way without elaborate test equipment. If basic voltage checks are good then alignment will have to be considered.
Concerns about a under-rated switch is misplaced. Tubes are usually Ok. These being locktal tubes there is concerned about pin connection issues. Rocking the tubes in the sockets can reveal a intermittent pin while listening to the radio.
http://www.nostalgiaair.org/Resources/497/M0013497.htm
Voltages were checked as well as audio output.All seem fine.
Have had tubes out for cleaning and testing.
Is there a way to check the volume switch that was replaced?
Thanks for the help.
murf
Posts: 190
Threads: 8
Joined: Oct 2005
City: Lexington, SC
Little hard to read the schematic. Thinks it reads 2 Meg total with a 1 Meg tap. Believe the tap is for improving bass at low volume. Beginning to think the volume control replacement was poorly executed. Verify resistance and presence of a tap on the replacement and associated wiring. Not unusual to see poorly done vintage repairs for parts shortages, etc. Might find a replacement if needed from Mark Oppat at oldradioparts.net.
Posts: 663
Threads: 142
Joined: Jun 2011
City: Elko,MN.
rghines1 Wrote:Little hard to read the schematic. Thinks it reads 2 Meg total with a 1 Meg tap. Believe the tap is for improving bass at low volume. Beginning to think the volume control replacement was poorly executed. Verify resistance and presence of a tap on the replacement and associated wiring. Not unusual to see poorly done vintage repairs for parts shortages, etc. Might find a replacement if needed from Mark Oppat at oldradioparts.net.
Will check it out when I can.
Thanks again
