[37silverstreak]

Hey everyone,
Just wanted to present my next project, the modest Philco 40-81 portable. Now, I have a lot of other more interesting sets waiting for my attention, but this little guy has a more personal place in my collection.
This little 40-81 was given to my dad for Christmas in 1940 when he was 10 years old. It is complete with even the original Philco identification card with my dads' name and address still attached to the handle! The chassis is in beautiful condition with 3 original Philco tubes in place (the 4th is a Sylvania replacement). Even the original rubber coated wire is still flexible! I don't think that this set has been turned on for over 50 years. I have a picture of this radio sitting next to dad on the running board of my grandpa's 1937 DeSoto when he was sixteen in 1946.
I came across it while cleaning out my grandmas house after she died in 1987 and has been sitting packed away since then.
My dad is now almost 83 and his health is not good, to the point where I'm forced to realize that he probably won't be with us much longer. That got me thinking about this little radio, so I dug it out of hiding. I plan on replacing the caps and resistors, and even though the original wiring is intact, i will probably replace the wiring as well.
I haven't rebuilt a battery set before. I believe that the A voltage is 1 1/2 volts and the B voltage is 90 volts, is that correct? i have a battery eliminator but you should also be able to power it with 9 volt batteries and D cell batteries for the filament voltage, right?
Any input would be greatly appreciated. Thanks!
Kevin

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[TA Forbes]

Hello, neat little set!

Yes and yes on your questions.

[Arran]

Not correct on the B+ voltage, for some reason they chose 67-1/2 volts for the B+ on this set rather then 90 volts like most battery sets do. I have the same model but it's a little more neglected, the back is missing, also one of the battery packs must have been left inside and sprung a leak as there is a rusted area on the back of the chassis. I wouldn't be surprised if either your set or mine still worked if power was applied, short running times, low voltages, and no heat tends to make the caps, resistors, and wiring last a lot longer. I would even consider restuffing the original caps as there are only four of them in there, it's not too hard with a toaster oven and a glue gun. The service info for this model is in my 1940 Philco service manual.
Regards
Arran

[TA Forbes]

I stand corrected!

[Ron Ramirez]

Very neat...VERY clean...and how often do you see one of these sets that still have the original Philco owner's name card and card holder attached?

By the way, don't forget the [img] and [/img] tags before and after each picture. That way we can easily see the great photos! (I added them for you above.)
http://www.philcoradio.com/phorum/showthread.php?tid=29
http://www.philcoradio.com/phorum/showth...p?tid=4371

[37silverstreak]

Hey everyone,
Well, after spending an afternoon on the workbench saturday, the little 40-81 lives again! I replaced all the paper (and the one electrolytic) caps. I was able to restuff all of them except the electrolytic which was too big to fit in the original cardboard tube. I also replaced all the resistors. I had wanted to keep them, but most had drifted quite a bit. I also kept the original rubber wire in place. The rubber insulation is still in fantastic shape! Still soft and flexible after 70+ years! All the tubes tested over 75%. I did however order a NOS Philco 1N7 tube so the set will have all Philco tubes and I replaced the dial cord.
I have the set working off my AES power supply and it plays surprisingly well even though it's operating off only 63v B supply and not the 67 and 1/2v that Arran mentioned. i still have to align the set.
I have a couple of questions. First, Does anyone have any tips on cleaning the fabric on the case or should I just leave well enough alone? Also, I want to build a battery pack for the set so it doesn't have to be tethered to my power supply to use. I've seen some pictures online of guys who have done this, so I would like to try my hand at building one. Does anyone have any information or pictures on the type of battery used for this set? I know the voltages are 1&1/2v A and 67&1/2v B and the pin layout, but what about physical dimensions? Also, As Arran stated the B voltage for this set is 67 1/2 volts. if I were to use 8- 9volt batteries that would up the the voltage to 72 volts. Even though it's within 10% of the correct voltage, would this do any harm to the set? Or, should I add a resistor to drop the voltage? Any insight is always appreciated. Thanks!'
Kevin

[Chris Cusick]

I used 8 9 V cells in a Motorola portable that used the same arrangement. It works fine although I think 7 for 63 V would have been OK too. Others will chime in but I don't think the voltage level here is that important. You can snap the 9V batteries together using their own connectors and make something very close to the size of the original 67.5 V battery.

[Arran]

I looked up the schematic again after this and it seems to note B+ readings of 69 volts so the special battery pack may have been in the 70 volt range rather then 67-1/2. I'm sure you could connect 72 volts to it without cooking anything, but if you are worried about it you could connect a few silicon diodes in series with the + side, or between B+ and B- to cut it down.
Regards
Arran

[codefox1]

Well here's a primer on a pretty simple way to make a b battery eliminator
http://antiqueradio.org/bsupply.htm. Mind you an isolation transformer would be wise, else you may create a shock hazard. Anything that supplies 60 to 90 volts will work OK.

For the filaments, you could use a couple of D Cells, or do a little more digging, and you may be able to get a small transformer that has both, say 110 volt and 6.3 volt secondaries, say salavaged from a piece of test equipment. Well then, you could then use a LM317 device to supply the correct filament voltage, the above quoted reference to supply the B+, and I think you would be done.

This has been summarized at least twice on this forum in more detail , but I just can't find it today. You know, senior moment. Somebody will remember and post.