keefer,
i attached a diagram of the vibrator i made and one of the tester for the AAR vibrator. i don't know a simple way to test the one i made other than to try it in the radio. if the AAR vibrator is good, the bulb will light up but be dim.
the 101 ohm resistors are 1 watt, altho i don't remember if you need that much wattage. the 47 ohm are probably just 1/4 watt. of course, you can experiment. i think you can use MJ2955 transistors in place of the TIP 36Cs. or any PNP that's rated at 15 amps.
curiously [to me], you absolutely have to remove the buffer capacitor to use my vibrator. and i'm guessing that you don't need it with any solid state vibrator. another curious feature of my vibrator is that it cycles at about 55 Hz, not 115 like the original and the AAR. even so, the radio works just fine.
for what it's worth, i fried an AAR vibrator once. there is another one out there, called aurora design, which is bullet proof. you have to solder it onto a 4-pin tube base or solder it into the radio.
i hope you'll let us know if the AAR vibrator is good and what you end up doing. good luck.
curious! and baffling. try checking the voltages i mentioned in an earlier post. if the vibrator is working, the AC and DC voltage readings will be 200+ volts. but if they are that high, the radio should work same as it does with the original vibrator.
i have to say that i "designed" the AAR tester on the fly and can't say with certainty that it is reliable.
maybe call AAR? http://www.antiqueautomobileradio.com/
good luck.
keefer,
do try removing the buffer cap. again, i don't think you even need it with a solid state vibrator.
your value of 682K for the buffer cap is puzzling. maybe you mean 682 uuf? = .00682 uf.
btw, "Of all the old paper capacitors, the buffer capacitor is the capacitor that is most prone to failure. Replacing the buffer capacitor is therefore essential." https://www.justradios.com/buffer.html
good to hear that the radio is "working." apart from the hum. pretty obviously, the buffer cap was bad. all the other waxy paper caps need to go, too. be replaced, that is. they should all have a votage rating printed on them along with the capacitance. this thread has links to various spec sheets with voltage ratings for many philco caps. https://philcoradio.com/phorum/showthread.php?tid=17750
the 2 electrolytic caps numbered 64 also need to be replaced. a 350V rating is plenty. 10 and 20uf are fie in place of 4 and 8. or anything in between. that should eliminate most of the hum, but any cap connected to ground is diverting some unwanted frequency to ground. the negative lead of the 8uf side of cap 64 connects to the case [ground]. because the voltage at the other end is even more positive. by a lot! 200+ volts. the positive ends of the 2 caps are connected to each other.
again, good luck.
Thank you very much.I replaced all caps except dual can cap.Ordered some caps 4.7 and 10 radial style.Will let you know how it works when I replace dual cap.Very much appreciate the guidance.
(This post was last modified: 09-22-2022, 07:01 PM by Keefer.)
Seems like something else is wrong.If i lay the radio on its side it will play with and without buffer cap with solid state vibrator.If i set the radio the normal way it wont play with buffer cap.The buffer cap is new by the way.Almost think something is loose or touching.Any thoughts?
Quote:Almost think something is loose or touching. Any thoughts?
Yes, include solder blobs, wire snips, poor contacts on the tube/vibrator sockets, component wires touching. Using modern (smaller) components, the leads will be much longer as the body is shorter. The use of insulated sleeving is a must. If no sleeving is available ,solid wire can be stripped of its PVC covering and used for sleeving. Not all PVC is happy with the heat of soldering and will flow at curves or shrink a bit, oops... New components on long leads in an auto radio should have the body of the component tacked to the chassis with electronic grade silicone. Vibration of a vehicle will work harden the lead wires and break the leads. The use of a "Popsicle" stick or a wooden dowel that can be used as an insulated probe to poke at the circuits will often disclose a fault. Heat from a small nozzle heat gun or a freeze spray can also help narrow the area of the issue. So will determining if it is audio, IF or RF or power supply.
Chas
Pliny the younger
“nihil novum nihil varium nihil quod non semel spectasse sufficiat”
Is the original mechanical vibrator good? Does the radio work in all directions with the mechanical vibrator? If so, possibly something wrong with the solid state one.
+1 0n Chas's ideas, they're great. If you can't get freeze spray but have "Canned Air Duster"(Available at Staples), turn the can upside down. CAUTION!! Make sure that the Air Duster is not flammable!
A useful technique is the "Tap Test". Hold a screwdriver by the blade and tap the entire radio, then tap individual tubes, transformers, etc.
One (somewhat scary) but useful idea is the "Drop Test". Pick up the radio about 1" above the bench and drop it.
Good luck!
"Do Justly, love Mercy and walk humbly with your God"- Micah 6:8
Best Regards,
keefer,
of course, the simple answer is - just remove the buffer cap. but, according to the AAR website, "Whether you use a Solid State or mechanical vibrator, both the radio manufacturer and the vibrator manufacturer recommend that you replace the buffer condenser each time you replace the vibrator." implying that the radio should have one even with a SS vibrator.
i have to agree with chas. that something is loose or touching. check the voltage at the rectifier tube with the buffer cap in place and with the radio oriented both ways. to see if you have high voltage when the radio doesn't play. also, try removing the AAR vibrator and connecting it on the bottom side of the radio with wires and alligator clips. that way you can rotate the radio and the vibrator separately and at least determine if the trouble is in the radio or in the vibrator.
quite the mystery. hope you're still having fun!
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