1954 Philco clock radio 

     Analog Dial           Page 1        Page 2        Page 3        

That was weird. What would cause it to go dead? Maybe a bad vacuum tube. One by one I swapped all the vacuum tubes but the set remained silent. Now I couldn't report back with the AVC voltage, but I had to start troubleshooting, so I started by checking voltages since that's what I was going to do anyway.
It was found they were too high coming out of the rectifier circuit. There were two reasons for this:

1. The schematic calls for 30, 25 and 20 mfd filter caps and I replaced them with 33, 33 and 33. This would cause an
    increase in voltage. However, the ones I removed were 40, 40 and 40, so I thought it was safe. (I figured the radio
    repair guy at Grosse Pointe Radio and Television knew what he was doing. For all I know he may have intentionally
    sabotaged the set so it would fail later. $$$)

2. The 220 ohm resistor was in reality only 160 ohms.

If the voltages are wrong here, they are wrong all over the entire radio!

Here's the 220 ohm resistor. I had to remove the new power cord to get to it.
I ordered some 220 ohm resistors and some capacitors to replenish my parts box. Also ordered some silver mica caps in case this thing had "Silver Mica Disease." Because they came from Canada, it took them 17 days to get here. By the time they arrived I was so busy doing other things I had almost forgotten about the radio. Work didn't resume till July 16. (Ironically, I didn't need any of the parts I ordered!)

Above, the clock from the bashed radio is being used to power the chassis while resistors are substituted to bring down the voltages.


It turned out that 220 ohms wasn't enough to bring the voltages down. It ended up with two 1500 ohm 1/2 watt resistors in parallel, which equaled a 750 ohm 1 watt resistor. The voltages are within four volts of what they should be.

I turned the radio on and... nothing. Dead as a door nail.

It was time to crack open the IF cans and look inside. Ugh, must be Silver Mica Disease.

I tried to pop the cover off one of the cans while it was still attached to the chassis, but it wouldn't come off. So instead, I cut one out of the bashed radio to see how it looked inside.

On the right is a close-up of what you can see of the capacitor. It's a real capacitor made of two metal plates, not a piece of mica with silver sprayed onto it.

Wait! It's a trick! It's a deception!! Those aren't metal plates, they're metal contacts! They touch the silver sprayed onto a piece of mica. Argh, the silver has migrated.

Why not just make the metal contacts into plates and put a bare piece of mica between them? I guess it was easier or cheaper to do it the way it was done. By the way, the capacitors are 100pf and 80pf, that's why they are different sizes on the mica.

There is the Silver Mica Disease, on the left. Atoms of silver from one capacitor are moving towards the other capacitor. When they meet you get a "pop" in the speaker. As more and more make the journey the pop turns into a torrent of static. It doesn't usually cause a dead radio, but it can happen.
It seemed I would have to operate on the IF cans, which I was dreading.  I turned the radio on and stared at the tube filaments warming up while I thought about it.

After about 30 seconds it came to life! Not only was it working, it was working better than it ever had! Instead of five locals, it was picking up everything! High power, low power, local, distant, far away stations, the entire band was full! Whoo-hoo!! I must have fixed a bad connection while I was pulling on the IF can cover. It was fixed!

It did not have Silver Mica Disease after all!!!
I told Andrea the radio was working but it was really bothering me that I didn't know what fixed it.

I was about to put the chassis back in the cabinet and turned it on one more time before doing so. It was DEAD! AGAIN!
Yes. AGAIN. DEAD. Deceased.

 It was working a minute ago!!!

I wasn't sure what to do at this point, so I changed tactics. I loudly slammed the silverware drawer shut. Nothing changed. I spoke to the radio in a James Cagney voice, then switched to Edward G. Robinson, see? Still nothing. So I threw my shoes down the steps after slamming the bedroom door 5 or 6 times.

Out of ideas, I sat down and forlornly started substituting tubes again. When I got to the 12BA6 the radio came to life! I put the original tube in, and the set was dead. I replaced it again and the radio came to life.

I had swapped out the tubes in June and they made no difference. Why was it working now? I tried it once more. Original tube - dead radio. Swapped tube - radio comes to life.

Remember, on page one the bashed radio suddenly came to life and then went dead. I believe both radios had the same problem with the same tube. Both radios had their filter caps replaced. Both sets were operating at higher than normal voltages and both 12BA6 tubes developed an intermittent problem. In this case, the 12BA6 had 108 volts on the plate, 48 volts higher than what it should have been.

Also, the red hot "tube saver" resistor is connected to pin 4, so instead of "saving" the tube, it may actually be killing it.

So apparently back in June, when I swapped the 12BA6 with the other, they were both in their "dead" state.
It was off to the garage to find a tube, and I found this "new old stock" 12BA6 that my buddy Joe Jones gave me years ago.

The radio now looks and works like new. I gave it to Andrea since this was all her fault to begin with. She volunteered to wear the same gown she had on in the video for this picture. All I can say is that it's a good thing I wasn't the radio repairman in the video, because the whole shoot would have been held up for months.

The 12BA6s were retested. One tested almost new, just as it had in May. I left it in the tube tester while I went outside and painted the garage window. When I came back the tube was dead. It was SO dead there was not the slightest deflection of the meter while pressing the test button. I tested the other one just in case there was a problem with the tube tester. The tube tester was fine. Into the trash can they went.

I tried to contact rjd2 to ask him about the radio in the video but he hasn't answered. The original video is posted here.

Large .jpg of the schematic can be seen here.
Sams Photofact Folder in .PDF can be seen here.
Riders manual for the radio can be found here.

We now return to our regularly scheduled program.