Sears Silvertone table radio, model 5021

[William]

I have been working on a Sears Silvertone table radio that was built by Arvin for Sears, chassis number 132-80001. It came in two model, 5020 which was a walnut plastic case and model 5021, the one I have, which came in a wood Early America maple cabinet. This was definitely a TOTL radio for Sears, having 8 tubes, a 5X7 woofer and a tweeter with crossover cap. It sounds quite good when it works. The down side of this radio, it has a PC board. Tube layout as follow:

17C9, 18FX6A, two 18FW6A's, two 18FY6A's, 50C5 and a 50HK6. No rectifier tube, it uses a diode as the rectifier.

Here's the odd part. The 50C5 is an audio output tube which makes perfect sense. The 50HK6A is also listed as a audio output tube. Both tubes are shown as audio output tubes in Sam's and on the tube chart in the radio. The schematic shows them in PP, I think, but how does that work with them not matching in number. I checked, and they do not sub for one another yet they are both used in the audio output circuit for this radio.

So, this radio had the "HUM", OK, I replaced the filter can cap with three component caps and all was well. NOPE, that did not fix the hum. Hmmm... I poked and prodded and discovered a bad solder joint at a resistor that I did not touch. Soldered that, and it worked until the next time I turned it on and the hum was back. Again, poked and prodded around and found another bad solder joint, and then another and another and another... After soldering a lot of connections it seems to be working but I almost hate to put it back in the cabinet, afraid the jarring of the PC board might cause another open contact. Moral of the story, be careful when you remove a 60 plus year old chassis in a radio with a PC board. Apparently the radio does not like that.

This is the radio:

https://www.radiomuseum.org/r/sears_roe ... _5021.html

The Sam's is 696-10. When I first started working on this radio I could not find any info on it. About month ago I started looking again and found the above link but no schematic. I kept looking and eventually found someone on ARF that included the Sam's.

https://antiqueradios.com/forums/viewtopic.php?t=276254

Go all the way to the end of this thread and you will find a a PDF that will open so you can see the schematic.

If anyone can explain the different audio output tubes I would love to know.

Bill

[electra225]

I'm not sure I understand why they used two different output tubes. Admiral and GE liked using 50HK6, 50HC6 and 35GL6 output tubes that nobody ever heard of and nobody else used. This radio uses low-filament-amperage tubes. There is a 5.2 ohm hum-bucking coil on the HK6 end of the output transformer. You might check to see it isn't open. My guess is they used two different output tubes to control hum, but I wouldn't swear to that in court....

Also check to see that one half of the output transformer primary is not open, that you have actually a P-P output rather than single-ended. One of those output tubes may not be working, which can cause a hum. Verify this by checking B+ at the plates of both output tubes. Is the hum controlled by the volume control? Do you have the 18FY6 and the output tubes that you can sub?

[William]

Actually, after pretty much soldering just about every connection on the PC board it is playing just fine. I slipped it back in the cabinet and it still plays. The next test is putting the back, back on. That is usually the death step.

Bill

[electra225]

Good job. ....

[danrclem]

I have confidence in you Bill and believe you have it permanently fixed.

[William]

Thanks, guys, but I am not out of the woods yet. Stay tuned!

Bill

[William]

Yup, as my luck goes, back installed on the cabinet and the hum is back. Here we go again!

Bill

[electra225]

Does that cabinet use an interlock on the power cord?

[William]

Yup!

Bill

[William]

Yup!

Bill

[electra225]

Since it always possible that something weird, out of the ordinary, may be going on, I asked about the interlock. Might it be possible that the interlock which is fairly rigid in the back, might be flexing the PCB enough that it is breaking a trace to the filter caps. You might take a good look at the traces and connections around the rectifier and filter caps. The heat from the rectifier might burn some of the traces. IT's worth a look at least.

[William]

I actually thought of that. After 60 plus years of heat and flexing it is a wonder it works at all. The PC board sags a little
in the middle which is where the interlock is located. The 2 output tubes are located to the left. I will get back to it sometime this weekend.

Bill

[electra225]

Bell wire makes good wire for hardwiring a printed board. Not all that tough, just tedious. The GE stereo I did for Don had about half the amp chassis hardwired and it's been running just fine for at least ten years now. My problem with running traces looking for a breach is something my eyesight is not good enough for anymore. Hardwiring is usually more successful than trying to resolder connections. Heat is likely what caused the breach, more heat from a soldering iron usually doesn't help any. Good luck.......