Firestone 4-A-159

This Firestone 4-A-159  “De Luxe Radio” from 1957 is one of a group that must have been the “tough dogs” from some radio repair shop. 

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Every one so far has some unusual problem that’s been difficult to troubleshoot. This one wasn't an exception.

The case and knobs are polystyrene. I made the mistake of soaking the knobs in high-test isopropyl alcohol in an attempt to get off all the grunge. They softened up and their shape was distorted  :-( So I’m having to make-do with random pair of knobs.

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Restuffing the filter capacitor for the Firestone 4-A-150

The radio is new enough to use ceramic capacitors and good-quality resistors, so all I initially needed to do was to re-stuff the electrolytic filter capacitor.

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I like using the 10 mm diameter capacitors. They are easy to fit into the old can. A little J-B Weld epoxy will hold the can back together.

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Since this was a PCB-mounted capacitor, I tried routing the negative common lead through a hole drilled next to one of the common pins. This worked out well.

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After re-capping, the radio worked only intermittently. I finally noticed that one of the tube socket pins wasn’t soldered to the pad on the printed circuit board.

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The tube sockets have a center pin, apparently intended to insert into a mounting hole with a PC pad. But the Firestone printed circuit board wasn’t designed for these sockets. The Arvin manufacturing line fixed the problem by cutting off the center pin with a pair of dikes. But this socket wasn’t clean-cut, and the protuberance prevented the socket from fully seating on the PCB. The pin nearest the bump didn’t fully reach the PCB pad, leading to an intermittent connection.

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A few seconds with a pair of dikes to trim the tip, and the socket was ready to be re-mounted.

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Since it’s a PC board, it doesn’t have convenient test points for connecting the signal generator for alignment. I soldered a pair of wires on to the appropriate traces.

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Of course during all this manipulation of the chassis, the connection to the loop antenna flexed enough to fatigue and break off. 

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Ready to be reassembled. I’m just getting in the habit of covering the speaker with a square of cardboard while I work on a radio. This one got a few punctures while I worked on it. I repaired them with Sobo fabric glue.

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One of the pads lifted while I was re-soldering the socket, so I added a jumper to ensure good contact.

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Aargh! I managed to get the ferrite core stuck on the first IF transformer. While trying to get it unstuck, I ended up destroying the IF transformer. 

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The Sams Photofact doesn’t list any replacement IF transformer part numbers, only the Firestone part number. But they are just ordinary 3/4 inch PC mount 455 KC IF transformers. Perhaps made by Automatic Manufacturing? They have the same injection-molded polystyrene frame as one that I know to have been made by Automatic.

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Mark Oppat at OldRadioParts.net says he probably has a Meissner or Miller replacement IF transformer that will work, so I’m looking forward to getting it working and aligned.

© Steve Byan 2011-2016