05-21-2020, 03:50 PM
Mike, Methinks you have it backwards! I fix these confounded things so I have something to grumble about. [Image: https://philcoradio.com/phorum/images/sm...on_eek.gif] I used to be nice but now I'm turning in to a curmudgeon.[Image: https://philcoradio.com/phorum/images/sm...lleyes.gif]
Back to the grind.
Oh I should edit my remark about the speaker plug fitment. If you use one from a model 20 it's a good match in that it can be mounted so the flat is parallel to the bottom of the chassis. Will need to shave a little off as it will hit the qavc control. Plus elongate the screw holes. The 1st attempt was with a socket from a 116 chassis. That one will mount cockeyed.
Swapped out the 2nd IF transformer and the set was dead as a door nail. Well the audio was working but no mixer or IF. GRRRRRR[Image: https://philcoradio.com/phorum/images/sm...n_evil.gif] After some troubleshooting I found that was no hv on the plate of the 2nd IF amp (kill me now!!!) [Image: https://philcoradio.com/phorum/images/sm...wisted.gif] Bart measured the coil to find it was OK. [Image: https://philcoradio.com/phorum/images/sm...n_clap.gif] While I was digging around in the chassis I noticed that there was two blocks I neglected to restuff. One was the grid bypass on the qavc tube which doesn't seem all that important. If it was a dead short the avc line would "see" it thru the 4M resistor. Not that much of a big of a deal. The other was a dual .05. One section is the cathode bypass the the 2nd IF amp. Still not a bid deal as the cathode is fairly close to ground anyway. The other section was the plate bypass for 2nd IF amp. Now were getting somewhere.
Both blocks got new cap inside. I did take note that there was only wire connected to the plate bypass cap. Thought that the b+ must be connected to the coil but that wasn't the case. The wire was missing! Put a jumper over to b+ and it sprang to life! I'm not sure where the wire went but it may have been part of the wiring that was added when the Ktran transformer was added as a replacement. If so the wiring incorrect in that the 2nd IF amp was getting it's b+ from the wrong side of the shadowmeter.
Back to the original problem. Intermittent short in the 2nd IF transformer. I found the problem. There was a dinky fleck of solder that attached itself the mounting bracket (chassis ground) and was a few microns from the hv terminal at the base of the transformer. That problem is solved.
Did a few ancillary things cloth line cord, pop the bakelite grommet back in, align IF, and adjust shadowmeter. It's playing and sounds good. Have put it back in the cabinet for the acid test.
Back to the grind.
Oh I should edit my remark about the speaker plug fitment. If you use one from a model 20 it's a good match in that it can be mounted so the flat is parallel to the bottom of the chassis. Will need to shave a little off as it will hit the qavc control. Plus elongate the screw holes. The 1st attempt was with a socket from a 116 chassis. That one will mount cockeyed.
Swapped out the 2nd IF transformer and the set was dead as a door nail. Well the audio was working but no mixer or IF. GRRRRRR[Image: https://philcoradio.com/phorum/images/sm...n_evil.gif] After some troubleshooting I found that was no hv on the plate of the 2nd IF amp (kill me now!!!) [Image: https://philcoradio.com/phorum/images/sm...wisted.gif] Bart measured the coil to find it was OK. [Image: https://philcoradio.com/phorum/images/sm...n_clap.gif] While I was digging around in the chassis I noticed that there was two blocks I neglected to restuff. One was the grid bypass on the qavc tube which doesn't seem all that important. If it was a dead short the avc line would "see" it thru the 4M resistor. Not that much of a big of a deal. The other was a dual .05. One section is the cathode bypass the the 2nd IF amp. Still not a bid deal as the cathode is fairly close to ground anyway. The other section was the plate bypass for 2nd IF amp. Now were getting somewhere.
Both blocks got new cap inside. I did take note that there was only wire connected to the plate bypass cap. Thought that the b+ must be connected to the coil but that wasn't the case. The wire was missing! Put a jumper over to b+ and it sprang to life! I'm not sure where the wire went but it may have been part of the wiring that was added when the Ktran transformer was added as a replacement. If so the wiring incorrect in that the 2nd IF amp was getting it's b+ from the wrong side of the shadowmeter.
Back to the original problem. Intermittent short in the 2nd IF transformer. I found the problem. There was a dinky fleck of solder that attached itself the mounting bracket (chassis ground) and was a few microns from the hv terminal at the base of the transformer. That problem is solved.
Did a few ancillary things cloth line cord, pop the bakelite grommet back in, align IF, and adjust shadowmeter. It's playing and sounds good. Have put it back in the cabinet for the acid test.
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 it!
Terry
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