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philco tropic model 42-760
11-09-2016, 06:07 AM
the wire with the white clip comes from the small transformer the other wire from that side of the transformer goes to pin 2 of both 42 tubes and the other two wires from the other side of the transformer goes to terminal lugs that connect to the blk and wht speaker wires
11-09-2016, 10:55 AM
Ok Now things are making sense! That transformer is the audio output transformer. The thing that was throwing me off track is that most of the time it's not mounted on the chassis but on the back of the spkr.
We need to test it to be sure that the primary winding is good (has resistance) and is not open (OL) So measure the resistance from your wht chip lead wire to pin 2 of one of 42 tubes then do like wise to the clip wire to pin 2 of the other 42 tube. If good should show around a few hundred ohms. Also measure from pin 2 of one 42 to pin 2 to the other 42. You mentioned that the spkr plugs in. Should have 4 connections, are for the voice coil and the other are for the field coil. Voice coil is mounted near the front of the spkr right behind the paper cone. We're not to interested in it but we are interested in the field coil. It's at the back end of the spkr and basically it's a big coil of copper wire that makes up part of the electromagnet that operates the spkr. Modern spkrs have a permimnate magnet (no electricity need). So we need to check it too. Unplug the spkr and measure the resistance of the field coil. Should be abt 800 ohms. On the spkr socket (on the chassis) should have 4 connections, two are grounded to the chassis one goes to the voice and the other to the field coil. The other two connections, one to the voice coil which ends up at the output transformer and the other is the field coil. If that is your loose wire it goes to the - side of the 15uf cap. When my pals were reading comic books I was down in the basement in my dad's workshop. Perusing his Sam's Photofoacts Vol 1-50 admiring the old set and trying to figure out what all those squiggly meant. Circa 1966 Now I think I've got! Terry
11-09-2016, 02:35 PM
first the speaker plug has 3 has three connections and also not the original speaker and when I measure the resistance I get 180 ohms two ways I try and 5 ohms the other way and from the wht clip to pin 2 of first tube 42 I get 360 ohms and to second tube 42 I get 317 ohms and from pin 2 to pin 2 of tube 42 I get 680 ohms
11-09-2016, 03:09 PM
Ok so your output transformer is ok and the wire with clip lead goes to the + side of the 40uf cap. I'm a little concerned about the field coil resistance as it's used the set the negative bias voltage in the set. With it being lower in resistance it will lower the bias voltage. I suppose if who ever change out the spkr may have add a series resistor between that loose wire and the - side of the 15uf cap @600 ohms at 15 or 20 watts. If not I would check the negative voltage on pin 4 of the 42 tubes should see about -15vdc.
When my pals were reading comic books I was down in the basement in my dad's workshop. Perusing his Sam's Photofoacts Vol 1-50 admiring the old set and trying to figure out what all those squiggly meant. Circa 1966 Now I think I've got! Terry
11-09-2016, 03:34 PM
ok you are saying the green speaker wire goes to negative side of 15 uf :the wire that goes to resistor 77 and on to power transformer goes to negative of 15 uf :the red wire that goes to resistor 16 goes to positive of 15 or 40 uf and the wht clip wire that goes to output transformer goes to positive side of 40 uf but just one question does the 40 and 15 still connect together at the positive side or will they be two separate ones now because in your earlier drawing they were connected and of course the negative side of 40 uf goes to chassis ground
11-09-2016, 06:49 PM
(11-09-2016, 03:34 PM)the picker Wrote: ok you are saying the green speaker wire goes to negative side of 15 uf :the wire that goes to resistor 77 and on to power transformer goes to negative of 15 uf :the red wire that goes to resistor 16 goes to positive of 15 or 40 uf and the wht clip wire that goes to output transformer goes to positive side of 40 uf but just one question does the 40 and 15 still connect together at the positive side or will they be two separate ones now because in your earlier drawing they were connected and of course the negative side of 40 uf goes to chassis ground > the green speaker wire goes to negative side of 15 uf Wire color is not listed what I can tell you is that one of the field coil wires goes to the chassis the other goes to the negitive side of the 15uf cap. >the wire that goes to resistor 77 and on to power transformer goes to negative of 15 uf Yes >wire that goes to resistor 16 goes to positive of 15 or 40 uf and the wht clip wire that goes to output transformer goes to positive side of 15 or 40 uf Yes >does the 40 and 15 still connect together at the positive side Yes > because in your earlier drawing they were connected and of course the negative side of 40 uf goes to chassis ground Read post #12. I drew the the diagram wrong that's why I deleted it and redrew it correctly. Forget the first drawing. BTW the - side of the 40uf cap does connect to the chassis the - side of the 15uf doesn't, it connects to 77, pt and fc. When my pals were reading comic books I was down in the basement in my dad's workshop. Perusing his Sam's Photofoacts Vol 1-50 admiring the old set and trying to figure out what all those squiggly meant. Circa 1966 Now I think I've got! Terry
11-10-2016, 07:47 AM
I put the cap in the radio and I get a little buzzing sound and when I touch the top of tube 75 I get a higher static noise and I checked the tube voltage on pin 4 of both 42 tubes and I get minus 1.6 dc v when radio starts to warm up and 0 dc v when the radio is warm and these measurements were taken from chassis ground
11-10-2016, 08:11 AM
>add a series resistor between that loose wire and the - side of the 15uf cap @600 ohms at 15 or 20 watts.
When my pals were reading comic books I was down in the basement in my dad's workshop. Perusing his Sam's Photofoacts Vol 1-50 admiring the old set and trying to figure out what all those squiggly meant. Circa 1966 Now I think I've got! Terry
11-10-2016, 08:24 AM
do you mean the green wire that went to the speaker and what else would work because it looks like the closest I have is a 1000 ohm at 10 watts
11-10-2016, 09:33 AM
if you have 2 connect them in parallel.
When my pals were reading comic books I was down in the basement in my dad's workshop. Perusing his Sam's Photofoacts Vol 1-50 admiring the old set and trying to figure out what all those squiggly meant. Circa 1966 Now I think I've got! Terry
11-10-2016, 09:54 AM
I connect two parallel and have a reading of minus 6.4 dc v and no change in radio but I have a bad feeling I have a bad volume control also because it crunches when I turn it and so when I tested the resistance from the centre pin to one side it has .2 ohm at high volume and .1 ohm at low and from centre pin to other side at high volume it has .600m ohm and at low it has .600m ohms and across the two outside pins it has .600m ohms
11-10-2016, 12:42 PM
(11-10-2016, 09:54 AM)the picker Wrote: I connect two parallel and have a reading of minus 6.4 dc v and no change in radio but I have a bad feeling I have a bad volume control also because it crunches when I turn it and so when I tested the resistance from the centre pin to one side it has .2 ohm at high volume and .1 ohm at low and from centre pin to other side at high volume it has .600m ohm and at low it has .600m ohms and across the two outside pins it has .600m ohms Schematic shows a volume control w/4 connections (2meg w/a tap at 1meg) On the other hand the tone control has 3 connections. Maybe your vc was replaced too. When my pals were reading comic books I was down in the basement in my dad's workshop. Perusing his Sam's Photofoacts Vol 1-50 admiring the old set and trying to figure out what all those squiggly meant. Circa 1966 Now I think I've got! Terry
11-10-2016, 03:14 PM
so is my voltage close enough now for the radio to work and do I need to replace the volume control thanks
11-10-2016, 04:06 PM
Your grid bias is low @6v. With 250v on the plate (pin 2) the - dc voltage needs to be -17 to -21vdc on pin 4 (grid 1). With that low of a bias voltage 2 things are going to occur. Distorted audio and excessive plate current flow on the two 42 tubes. Not good for the 42 tubes.
http://www.mif.pg.gda.pl/homepages/frank...1/4/42.pdf Wouldn't worry too much about the vc yet I'd get the set to pass a RF or IF signal. Do you have a signal generator? When my pals were reading comic books I was down in the basement in my dad's workshop. Perusing his Sam's Photofoacts Vol 1-50 admiring the old set and trying to figure out what all those squiggly meant. Circa 1966 Now I think I've got! Terry
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