01-20-2013, 02:51 PM
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
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
