Good morning,
I am working on one of these.
Can someone please tell me what ecaps this uses? I am confused by the different schematics I have and ehat is currently in my radio. Also there is a resistor 80 ohm I believe mounted the the chassis. Can someone tell me what wattage I should use for this and does it have to be mounted to the chassis?
Thanks
Chris
Hi Chris,
http://www.nostalgiaair.org/Resources/584/M0013584.htm
I looked at the 122 schematic from nostalgiaair.org and it appears the electrolytic caps in your chassis have been replaced. The schematic shows 3 caps in the power supply; 30-25-20 mfd 160v. All 3 were originally contained in one tubular part. Your photo shows 4 individual caps so you must be careful to trace out the wires and locate the points they are connected. Then you will have to determine the extra cap and why it is there. The resistor is R17 in the schematic which is a candohm wirewound dropping resistor of 83 ohms in the filament string. You can replace it with a 10 watt 85 - 90 ohm resistor. I usually put the replacement across the terminals of the old one after removing the wire guts. Take your time with replacing the caps because you don't know what the intention of the person who installed them was.
Rod
Rod,
The 128 uses a voltage doubler circuit rather than the half wave rectifier that the 122 uses. The voltages listed on the schematic are low enough that you should be able to use 250v units. A pair of 22mf (101 & 102)and a 47mf (104's) should be fine.
Thanks Terry. I had a feeling there might be a different way of confusion
. So 2 of the caps are used for the doubler and maybe the other 2 for filtering? Chris will have to be careful to connect the 2 doubler caps correctly.
C-101 charges up during the positive cycle of the ac although it's dc after going thru the rectifier. C-102 charges up during the negative cycle. C-104 is what is know as a brute force filter which means it's a high value cap.
Can you help me figure out exactly where the ecap connections are? Still trying to figure out reading the schematic.
thanks
Chris
Can someone please help me.Have recapped the radio. Replaced the resistors. The radio starts fine for awhile but twice now the two 16 ecaps swell and start smoking. I bring it up slowly on a variac. I smell smoke and those two caps swell. What am I doing wrong? Originally there were 40s in their. Should I try that? Can some one verify that my connections are ok? I was always under the impression that the negatives if the ecaps should be connected together. This one has the negatives at different locations? Went through two sets of ecaps so far.
Thanks
Chris
I edited post 7 reread. On pg 168 there is a diagram of your power supply but you'll have to re number the tube pins as Philco changed the tube on run 127.