05-09-2019, 09:35 PM
The rivets are firm to the chassis, and the grid wire is run through one of the rivets, which is the same as the Code 121, which puts it inside the shield. I see no signs this chassis ever had a shield around that tube, especially since it would take a very deliberate action to remove the ring and reinstall rivets. People who would hack into a radio would not be expected to cover their tracks like that.
By the way, I've tried several different tubes in both positions, and in fact, both of those "balloon" tubes have been pulled to be saved for a more special radio. (The original Balloon 42 howled more than the Ken Rad shoulder tube that lives there now.)
No loose solder joints either. Experimentation indicates the howling is affected by the incoming signal (spikes in audio or loud volume can trigger it), and hand placement around or between the audio tubes.
I believe shielding is the needed solution based on that, but I would like to see how the original Code 125 chassis handled the issue if they eliminated the ring on the chassis side.
If anyone has another Code 125, 225, or similar 71 series chassis with individual shields around the RF tubes, I'd be very interested in seeing how it was done.
The picture you're looking at is how I got the radio, before I worked on it, and the grid wire has been replaced because the insulation frayed around the rivet hole, and I was losing audio altogether. (That problem, at least, is fixed.)
What I don't want is to bodge a shield that wasn't on the original radio, unless they all were known to howl without the shield around the 39/44 after Philco removed the original shield. What I do want is to discover if Philco used some different type of shield around that tube, or some other solution and see if I can find one just like it so my radio is more authentic.
I'm sure I could stick a non-correct Goat shield around my now ST type 39/44 and solve the problem, but that's not what I'm after. I really want to know how these Code 125s originally worked without howling.
Dan
By the way, I've tried several different tubes in both positions, and in fact, both of those "balloon" tubes have been pulled to be saved for a more special radio. (The original Balloon 42 howled more than the Ken Rad shoulder tube that lives there now.)
No loose solder joints either. Experimentation indicates the howling is affected by the incoming signal (spikes in audio or loud volume can trigger it), and hand placement around or between the audio tubes.
I believe shielding is the needed solution based on that, but I would like to see how the original Code 125 chassis handled the issue if they eliminated the ring on the chassis side.
If anyone has another Code 125, 225, or similar 71 series chassis with individual shields around the RF tubes, I'd be very interested in seeing how it was done.
The picture you're looking at is how I got the radio, before I worked on it, and the grid wire has been replaced because the insulation frayed around the rivet hole, and I was losing audio altogether. (That problem, at least, is fixed.)
What I don't want is to bodge a shield that wasn't on the original radio, unless they all were known to howl without the shield around the 39/44 after Philco removed the original shield. What I do want is to discover if Philco used some different type of shield around that tube, or some other solution and see if I can find one just like it so my radio is more authentic.
I'm sure I could stick a non-correct Goat shield around my now ST type 39/44 and solve the problem, but that's not what I'm after. I really want to know how these Code 125s originally worked without howling.
Dan
"Why, the tubes alone are worth more than that!" (Heard at every swap meet. Gets me every time!)
Philcos: 90, 70, 71B, 610, 37-61 40-81, 46-420 Code 121 to name a few.
Plus enough Zeniths, Atwater Kents and others to trip over!
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