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38-116 broken wire in sub-chassis - Printable Version

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38-116 broken wire in sub-chassis - murf - 11-29-2015

Hi Guy's,
I have a request for detailed instructions on how to remove the sub-chassis on my 38-116.
Appears there is a broken hair like wire broken.
Its in the mid-section where the 6L7 tube is.
There are caps that need to be replaced as well.
I remember reading info on this repair on here before, but I cannot find it now.
I know the tuning dial assembly has to come off as well as the tuning capacitor and about 7 or 8 wires.
Don't know if I am brave enough to attempt this job, but if I had instructions it would help.
I am sure they have probably written a book on this subject.
Wish I could just hire someone to do it for me.
Anyone?
murf

RE: 38-116 sub-chassis removal - klondike98 - 11-29-2015

Can't help much but did find a comment by Ron that indicates the code 125 sub assembly is different from the code 121 assembly....and he did use the word "complicated". Icon_smile

John k9uwa from John and Jean Antique Radio posted some pics and comments for a 37-116.

38-116 question - murf - 12-01-2015

Have a question regarding my 38-116.
Noticed in the center section of the sub chassis that there is a broken wire. Very fine wire that I think goes to item 16 on the schematic which is the RF trans. (range 1). Yet the schematics and parts list show a wire wound 400 ohm resistor(item 13) from the trans. to the tube socket pin that has item 14(.05 condenser) attached to it as well.
I do not see the wire wound resistor under there.
Far as I can tell, the cap is run to ground. The resistor looks like it runs parrallel to the cap on the schematic, both going from the tube pin on one end and to ground on the other.
Should be a wirewound resistor from the tube pin to the transf 16.
Can someone decifer this area for me?
Anyway I could scrape off a small spot of the wax and somehow attach the wirewound resistor 13 to trans. 16?
Looks like a real nightmare to work in there without pulling the whole frickin radio apart.
Schematics are confusing in this area.
murf

RE: 38-116 sub-chassis removal - Ron Ramirez - 12-01-2015

I merged your other thread into this one, Murf, since both ask about a broken wire. Multiple threads on the same subject are not allowed.
http://philcoradio.com/phorum/showthread.php?tid=4586
Hang on, Terry, Morzh, and the cavalry are on their way to help...

RE: 38-116 broken wire in sub-chassis - murf - 12-01-2015

(12-01-2015, 09:55 PM)Ron Ramirez Wrote:  I merged your other thread into this one, Murf, since both ask about a broken wire. Multiple threads on the same subject are not allowed.
http://philcoradio.com/phorum/showthread.php?tid=4586
Hang on, Terry, Morzh, and the cavalry are on their way to help...

Thanks Ron,

RE: 38-116 broken wire in sub-chassis - Radioroslyn - 12-02-2015

The 400 ohm resistor needs to go from pin8 of the 6L7 to chassis gnd. I would suspect the the rf transformer lug is grounded also.

Terry

RE: 38-116 broken wire in sub-chassis - murf - 12-02-2015

Hi Terry,
So if I understand correctly, I could install the 400 ohm wirewound in parallel with the .05 cap.
That also goes from pin 8 to ground.
I have another ground tab on the sub chassis that I could use so that I could install new cap and resistor without having to put them down inside where the originals are.
Any extra wire wound resistors in your stash?
murf

RE: 38-116 broken wire in sub-chassis - Radioroslyn - 12-02-2015

I'd disconnect the cap and measure the resistance from pin 8 to gnd and see if that 400 ohm resistor is just hiding. If it came that way it wouldn'n work at all.

Terry

RE: 38-116 broken wire in sub-chassis - murf - 12-02-2015

Well I found that the broken wire was the resistor and was held onto the end of the cap with a big solder blob.
If I moved the blob around I could get reception.
I will have to replace both and see.
Only wire wound 400 ohm  resistors I could find were on ebay, but only in 3.25 watt.
Would that work instead of the 1 watt?
Mouser wants you to buy a bag of 100 with a 10 week delivery.
Found a friend of mine has one I can steal tomorrow.
Nice to have friends close that I can turn to in a pinch.
Thanks Terry,
murf

RE: 38-116 broken wire in sub-chassis - klondike98 - 12-03-2015

Radiodaze has a 5 watt 390 ohm for sale. Higher wattage is no problem other than it will be larger in size. They also have some 2 watt metal oxide resistors at 390 ohms.

RE: 38-116 broken wire in sub-chassis - Radioroslyn - 12-03-2015

I'm not quite sure why they are using ww resistor there. Typically it's a cc resistor and a 1/2 job. The ww may add a slight amount of inductance to the cathode circuit which it may need to operate on the SW bands. Not sure.

Terry

RE: 38-116 broken wire in sub-chassis - murf - 12-03-2015

Hi guy's,
Well I got lucky today and got a ww from a friend.
Put it in and the radio is playing and recieving on all bands again.
Now I want to try to figure out why it is not as strong as it should be on the audio side.
After it warms up a little it starts to get distorted and the sound quality diminishes a little.
I am thinking like a weak tube on the audio side.
What would you guy's look at if the tubes are ok?
I could go through the audio side and check resistors and caps again I suppose.
I did re-cap this thing and I replaced a handful of resistors.
Anyway, thanks for the help you guy's offer.
Invaluable service to hobbiests like myself.
murf

RE: 38-116 broken wire in sub-chassis - murf - 12-03-2015

Tested tubes and found the 6R7G almost dead.
Probably why I am having trouble on the audio end.
If I can find a tube on ebay, I think I will wrap it up.
Thank God I did not have to pull the sub chassis.
murf

RE: 38-116 broken wire in sub-chassis - murf - 12-09-2015

Update on the 116.
Got another 6r7 and tried it.
Did not help.
After it warms up a little the sound quality still diminishes and gets distorted.
If I increase the volume, it gets a little louder and along with increased volume comes the distortion.
Something is wrong in the audio side.
If the output tranny was going out, would this happen?
Or,is it a matter of working or not working?
Any chance it could be a speaker related problem?
Pulling my hair out on this one.
murf

RE: 38-116 broken wire in sub-chassis - Radioroslyn - 12-09-2015

Doubt it's the opt. I'd check the voltages on the 6L6 and the 6F6 tubes after it's warmed up. Suspect are the negative voltage on pin 5 or the positive on 3 or 4. You can also use a signal tracer to track down the distortion.

Terry