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 Post subject: Help To Repair a Philco 38-3
PostPosted: Apr Thu 09, 2020 7:45 am 
Member

Joined: Apr Wed 03, 2013 2:49 am
Posts: 228
Location: Laredo TX 78045
Dear Friends I have had this radio for at least 5 years. Never hear it working. A friend from Nebraska(now living south Texas) made a serious attempt to make it work. Here his recap on the job done
"In early 2018, I was in communication with Oscar Hernandez of Nuevo Laredo, MX regarding a Philco radio, model 38-3 he wished to have repaired. In November of that year I moved from Nebraska to Texas and made arrangements with Oscar to receive the radio chassis to commence the repair work.

Upon receipt of the chassis from Oscar, I noted a number of irregularities in the work that had already been performed. There were wiring issues, a burnt & broken tube socket that should have been replaced, a number of capacitors had been replaced but not with values or types that met original design circuitry. Further, there had been nothing done with the potted bakelite components that house capacitors. And, it did not appear that any resistors had been tested for proper values. It is a known phenomena where carbon resistors will vary in resistance values over time and end up substantially out of tolerance.

I began working through these issues and attempted to correct each as I found them. I first went through and replaced all (ALL) of the wax capacitors with new, known-good components and also replaced the can-type filter capacitors with new ones. I removed every potted capacitor pack, removed the potting and old capacitors, and reinstalled new capacitors in their place.

Next I methodically went through each and every resistor. Lifting at least one end (to isolate for testing), checked the resistance value and either reconnected the component (if found good.. but most were not) or replaced the ones that tested bad with new, properly sized (to meet or exceed the value & current-handling capability) resistors.

I replaced the one tube socket that had been badly burnt and broken as well as replaced (one conductor at a time) all of the aged & broken wires within the chassis.

I also tested and ended up replacing nearly every tube that came with the chassis from Oscar.

Working on it a short time each day, it took the majority of the winter months of 2018 & 2019 (November through April) to get this far. The last known condition I witnessed on the bench, I could inject an audio signal at the volume control and had great audio through the last pre-amp and push-pull amplifier circuit. The original speak sounded very good. I was able to inject RF signals at the front end (Antenna connection) as could trace it up to and basically through the oscillator circuit but that signal was not being coupled to the audio circuit. I suspect that the oscillator tube or something else in the oscillator circuit has now failed and will not allow proper signal to get through.

During the later portion of this time, I developed health issues that make it nearly impossible to safely do any testing or troubleshooting in circuits where voltages are potentially lethal. It was at that point that I boxed everything up. The chassis, as it was, the new parts that I had not had a chance to install. Along with these parts, I also have some ‘very old’ vacuum tubes that Oscar had removed from another vintage set he was working on at home and sent to me . I did not have my good tube tester with me at the time and when I did get to it back in Nebraska, it had some failed components in it. It, like many of my projects, has been put on indefinite hold due to health issues. So.. I was not able to test the tubes for him. He would appreciate very much if someone could test them and let him know the status of each.

One additional note to be aware of. ALL of the radio chassis parts that belong to Oscar have been sealed up inside a large box since long before the current pandemic began. There is no contamination issues with any of the parts or equipment. And.. also in the box with the equipment is all of the schematic diagrams and radio literature I had collected before and during my repair attempts.

I will make my contact information available to anyone that takes this project on such that I may be able to answer questions on"
Ok, is there anybody(close to San Antonio, Houston or Dallas area willing to finish this project?


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