Model 71 Code 221 Mystery Cap - Printable Version
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Model 71 Code 221 Mystery Cap - Night Sky - 12-09-2017
Greetings All,
This is my first post, so hello!
After several successful guitar amp and tabletop radio resurrections I was pretty excited when a Philco Model 71 Code 221 “High Boy” showed up on the local trader for $20.
It was missing four tubes, the cone of one of the two speakers was pretty torn up and it was thick with barn dust. I started with compressed air and 95 years of dust, pet dander and Heaven only knows what was liberated to the Wyoming wind.
I pulled the chassis and restuffed the two large filter caps and ordered tubes. I pulled the tuner and performed a thorough cleaning, re-lubed it with high-temp grease and remounted it on tapered faucet washers which brought the dial back up to where it should be on the front.
I replaced the power cord and after a thorough inspection and numerous meter short checks, and (not having a variac) I connected the plug in series with a 5 watt incandescent night light bulb and with a volt meter connected the cord to the mains and turned the power switch on and began monitoring the voltage. As the caps charged the voltage stabilized at about 35V, the dial lamp had a dim glow and I watched the night light bulb closely for signs of arcing. I operated it for about an hour, all the time sniffing, feeling and listening for any potential problems. Satisfied with that step I moved over to a 40W bulb and repeated the same steps. The voltage went to about 74V but there was no sound, although the 80 rectifier started to warm up. I finally switched bulbs again to a 75W and finally heard a little static in the speakers. I then put in a 100W and Charlie Daniels (sounding more like George Burns) began to sing from the speakers. The voltage was around 84V.
I could get three stations without the antenna connected but the speakers sounded horrible. I ran it like that for a few hours and the sound improved as the grit started shaking out of the speakers. Up until then I was pleased with my work, but I knew I was flirting with disaster. I needed to increase the voltage, so I went to the shop and grabbed a 300W construction light, removed the 100W bulb and connected the 300W it in series. The radio sounded 100% better, I assume because the field coils on the speakers were finally getting enough power. The volt meter said 118V but I didn't dare go beyond that. Oddly, my isolation transformer was bumping the power from 124V to about 135V, so I took it out of the loop for the test. That is another topic at some point.
I couldn't find any sources for speaker parts, so with nothing to loose I embarked with scissors, construction paper and rubber cement and “repaired” the torn speaker.
A few days later I put everything back in the cab and turned it on, still going through the shop light, and it sounded great! At some point I am sure I will have to do more with the speakers, but for now I'm pleased.
The speakers were loose with no gritty sound, I took some pictures and knowing that it was on borrowed time I shut it off and decided I would replace the rest of the capacitors, except for the micas and all the resistors before I turned it on again. Which brings me to this:
I've scoured the different regular sources and I have been able to come up with a list of caps and resistors that I will soon be ordering, except my radio has an additional two-wire metal sardine cap that has no identifying numbers on it and I can not locate on the layout or schematic. I'm wondering if anyone has ever run into this and could steer me in the right direction? It is the cap just above the long resistor coil on the bottom sitting at about forty five degrees.
Thank you!
RE: Model 71 Code 221 Mystery Cap - Ron Ramirez - 12-09-2017
That is most likely part (48A), 0.25 uF.
http://www.philcoradio.com/images/phorum/schem/71.jpg
It - and the long resistor below it - were only used on two-speaker console models. Single speaker versions did not have that resistor or capacitor.
Oh - and welcome here!
RE: Model 71 Code 221 Mystery Cap - klondike98 - 12-09-2017
Welcome to the Phorum!
RE: Model 71 Code 221 Mystery Cap - morzh - 12-09-2017
Welcome!
Great job, especially considering the lack of equipment.
If this is a one time thing, you at some point might do a proper speaker reconing and enjoy it.
If t is a beginning of a beautiful friendship between you and archaic electronic equipment, you might invest in a Variac, especially considering a 500kVA type is below $100. Mich more convenient and manageable than lightbulbs.
Mike
RE: Model 71 Code 221 Mystery Cap - Night Sky - 12-09-2017
Thank you Ron
The schematic is just what ive been looking for!
Munch appreciated.
RE: Model 71 Code 221 Mystery Cap - Night Sky - 12-09-2017
Thanks Bob.
RE: Model 71 Code 221 Mystery Cap - Night Sky - 12-09-2017
I would have to agree with you on the variac. The bulbs method works, but can be a tad cumbersome. Where have you seen one for under $100? Christmas is fast approaching so I'll have to drop some hints. Also agree with the cones. Who does them? I saw a name but couldn't find it again.
RE: Model 71 Code 221 Mystery Cap - Electrothaumaturgist - 12-09-2017
When you do the bulb thing, don't you start with the highest wattage bulb first?
RE: Model 71 Code 221 Mystery Cap - morzh - 12-09-2017
I think you start with lowet wattage, then again I never use t.
The idea is, the lower the wattage, the higher the resistance, so it drops more.
RE: Model 71 Code 221 Mystery Cap - Electrothaumaturgist - 12-09-2017
Naw... You want a bulb of about twice the wattage rating of the radio, if there are no shorts, the bulb will glow dim. If there is a short, it will glow very brightly, protecting the radio.
What an excellent Phind foir $20
RE: Model 71 Code 221 Mystery Cap - Stall-U-Rated - 12-09-2017
Tapered faucet washers????... I LOVE IT!!... Did the same to a 37 delco. I keep an assortment of them handy just in case..
Steve
RE: Model 71 Code 221 Mystery Cap - Night Sky - 12-10-2017
The wshers fit perfectly. I'm glad to hear that you'v used them too.