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Philco Mod 91 code 221 no reception - Printable Version

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Philco Mod 91 code 221 no reception - rlloyd898 - 01-30-2011

Hi there, I acquired a Philco Model 91 code 221 from my inlaws. I recently recapped the radio including the electrolytics. I had the vacuum tubes all tested and they passed. I cleaned the entire chassis and checked all the wiring for connections. I connected a 10 ft piece of speaker wire to the Ant and Gnd to attempt to pull in some signal. When I powered up the unit I just get a slight hum but receive no stations. When I move the tone switch it does change the hum slightly. I did notice the glow on the #36 Det Oscillator tube was significantly dimmer than the others. My mother in law unfortunatley said a few years ago that they plugged it in to see if it worked and did received some stations, however in the process they may have overheated the filter choke part 4819 because there was wax that had leaked out. It did check out though at 265 ohms so I think its still ok. It did find a few resistors out of speck ( the two 1 Meg resistors were around 1.5 megs). The push pull input TF part 6064 tested at 1950 ohms on the 2 wire side but only around 1600 ohms on the 3 wire side which according to the schematic should be 2400 ohms. Do you think that TF could be the problem? Also when I soldered in the 2 electrolytics, I disconnected the original + and connected the wires to the + on the new ones but soldered the negative ends to the original electrolytics neg where the other wires were soldered to. Should I have completely disconnected the negative end from the orig electrolytics and soldered the new electrolytics neg end to the wires? I thought that maybe the neg end had to be grounded to the chassis like the original electrolytics. Sorry about the long note, I just wanted to give you a lot of info to go with. I would certainly appreciate any info you can give me.
Thanks,
Ron L. Holly, Mi.

Re: Philco Mod 91 code 221 no reception - Radioroslyn - 01-30-2011

Hi Ron and Welcome
For starters clean up your 36 tube and socket. How's the high voltage? The input transformer primary seems good the secondary you need to measure from the center tap to each end to check to see if one side is open. If one side is open the set would play just not very loud and you won't have any grid bias on the tube with the open winding. Looks like the negative leads of the filters all go to the center tap of the hv winding.
http://www.nostalgiaair.org/PagesByModel/884/M0013884.pdf
Terry

Re: Philco Mod 91 code 221 no reception - rlloyd898 - 02-07-2011

Hi there and thanks for the info. I'm getting 720 VAC between the 2 p's at the rectifier and approx 400 VDC to the 2 F's. I'm also finding 380-400 volts around the choke. I'm also getting that similar voltage to the output TF on the speaker. I cleaned the 36 tube and socket but it is still dim. I did find a problem with part 6287-C, I replaced the capacitor but was supposed to have a 200ohm resistor there. I added it to the circuit(number 9 on the schematic). I was probing at the coils underneath checking for ohms and may have found an open circiut on the Oscillator coil (number 19) but it was difficult for me to diagnose. however when I plugged it in and turned it on I got a sizzle and could see some sparking on the Detector transformer (number 12). I immediately unplugged it. I dont know if I made a short while probong under the coils or if the soldered in resistor caused it. I simply solered it to each side of the capacitor as shown in the schematic. either way I think that coils' fried. Do you think I should go ahead and just try to find a new Det TF and/or Oscillator coil?