09-08-2026, 12:35 PM
Hello NorthCapNerd and welcome to the Phorum.
https://philcoradio.com/library/download...20Book.pdf
First off when you reference a specific chassis you are working on it's wise to supply a link to a schematic, if possible, so we are all on the same boat. If you have a schematic from Beitman and I get one from the Phorum library the parts will be labeled differently. So let's dig in. Yes your volume problem is connected with the feedback circuit from the output transformer. If you look at the schematic from the library the volume control and tone control get the ground reference they need from the tap on the opt secondary winding. Since the tap is on the secondary winding it is essentially at ground potential since the resistance of the winding is only a couple ohms. You'll notice the tap is connected to the wiper of the tone control and the bottom of the volume control. Without the tap you should be able to connect the wiper of the tone control to ground and restore the full function of the volume. The purpose of the feedback is to provide a small negative feedback that reduces audio distortion at the expense of a reduction in gain. The German radios of the late 50s, early 60s used this technique extensively. One thing you want to do is be sure the controls have been cleaned, preferably with Deoxit F5.
Here's my take on the speaker. Speaker cones are rigid, so they can push air. If you use something soft to make a repair then the rigidity is compromised. I use rigid paper and acid neutral adhesive to repair a cone. A surround has to be flexible, so repairs should have flexibility. I use flexible paper and contact cement for this. Some surrounds were in such bad shape I used the contact cement all the way around. Improved the bass response greatly. I have purchased surrounds on eBay and Amazon, there are many available. Measure carefully. The ones I replaced came out great. There are many videos on YouTube. You have to use spacers to keep the voice coil centered.
Noone likes dirty tubes. IF YOU USE WATER OR A CLEANER TO CLEAN YOUR LOCTAL TUBES YOU WILL NOT HAVE TUBE NUMBERS ON YOUR TUBES. You must be cautious with mineral spirits. Put some on a cloth and wipe gently checking the lettering as you clean. Some say if the number is printed on the top it's OK, but if you aren't cautious, you get one chance.
Have at it and keep us posted.
https://philcoradio.com/library/download...20Book.pdf
First off when you reference a specific chassis you are working on it's wise to supply a link to a schematic, if possible, so we are all on the same boat. If you have a schematic from Beitman and I get one from the Phorum library the parts will be labeled differently. So let's dig in. Yes your volume problem is connected with the feedback circuit from the output transformer. If you look at the schematic from the library the volume control and tone control get the ground reference they need from the tap on the opt secondary winding. Since the tap is on the secondary winding it is essentially at ground potential since the resistance of the winding is only a couple ohms. You'll notice the tap is connected to the wiper of the tone control and the bottom of the volume control. Without the tap you should be able to connect the wiper of the tone control to ground and restore the full function of the volume. The purpose of the feedback is to provide a small negative feedback that reduces audio distortion at the expense of a reduction in gain. The German radios of the late 50s, early 60s used this technique extensively. One thing you want to do is be sure the controls have been cleaned, preferably with Deoxit F5.
Here's my take on the speaker. Speaker cones are rigid, so they can push air. If you use something soft to make a repair then the rigidity is compromised. I use rigid paper and acid neutral adhesive to repair a cone. A surround has to be flexible, so repairs should have flexibility. I use flexible paper and contact cement for this. Some surrounds were in such bad shape I used the contact cement all the way around. Improved the bass response greatly. I have purchased surrounds on eBay and Amazon, there are many available. Measure carefully. The ones I replaced came out great. There are many videos on YouTube. You have to use spacers to keep the voice coil centered.
Noone likes dirty tubes. IF YOU USE WATER OR A CLEANER TO CLEAN YOUR LOCTAL TUBES YOU WILL NOT HAVE TUBE NUMBERS ON YOUR TUBES. You must be cautious with mineral spirits. Put some on a cloth and wipe gently checking the lettering as you clean. Some say if the number is printed on the top it's OK, but if you aren't cautious, you get one chance.
Have at it and keep us posted.
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