Hi Guy's,
Checking and replacing some resistors on my 116 and found that one of the wire wound resisters is checking out of tolerance.
Should be 14,000,checks about 9.5k.
Don't know what watt this resistor is.Not specified in the parts list.
Looked at antique electric supply and they have either 5 watt or 10 watt.
But they don't list a 14k ohm.
What combination of resistors would I need to get to come up with 14k?
And what watt would I want.
THis is listed on the parts list as schematic number 79.
Could this out of tolerance resistor be causing my floating volume problem I am noticing?Seems to drift up, then down.
Thanks for the help guy's.
I learn a little more everyday.
murf

Hi, murf, when I need odd resistors, I go here,http://www.surplussales.com/sitemap2/Rlist.html, lots of variety, and fairly fast shipping. They do have a 10.00 minumum, but I always order a few of the values I see fairly often, or will have in a set coming up.

Hi Murf

R79, 14K wire wound, is in parallel with R78. Are you sure you aren't reading combination of both? Unusual for wire wound resistors to change value.

Also this resistor may have been selected and changed at the factory? Unusual to see two different values paralled in a radio.

http://www.nostalgiaair.org/PagesByMode ... 013234.pdf

If you need this resistor try mouser electronics.

if R78 is a 70K resistor with R79 being as 14K resistor the combined resistance should be 11.7K.

I am only seeing the 79 wirewound resistor.Has 2 solder terminals.
Do not see 78 in parallel.
When checking 78 I am reading 9.5-10.0.
Still don't have a clue what watt resistor this would be.
Thanks
murf

As noted by Norm, unusual for radio schematic to show parallel resistors.
Wattage needed depends upon actual resistance value expected in that location.

Parallel resistors means voltage across them is identical and dissipation for each is a ratio of their Ohmic values.

# 79 is 1/5 the Ohmic value of # 78.
# 79 would be subject to 5 times the wattage dissipation of # 78

# 78 is rated 1 Watt
# 79 would see a max of 5 Watts
A single resistor instead of two parallel would see a max of 6 watts.

Order a ten Watt resistor.
But you still need to determine which Ohmic value is correct.

Deleted

Did you remove the wires from the terminals when checking the
resistance? That would be the first step that I'd try. Also, there
were two revision codes for that chassis, 121 and 125. That might
explain the differences in wiring you are seeing???

Pete

Yes, they're reading the same because they're in parallel as others have mentioned. If you remove one leg of 78 and then remeasure each, you'll find what their true values are.

I just started working on my 38-116 code 125 and noticed that several of the carbon resistors are swollen in the middle. Is the first time I have seen this. Is it a flaw in the resistors manufacture or sign of an electrical problem that occurred at some point?

I will be replacing them anyway, but I am curious.

Steve

Hi guy,s
I must have had a brain fart going on when I wrote the previos 1 or 2 posts.
I kept refering to checking the R78.
All I have is the R79(14k wirewound).
Do not have the R78 in my 121 code radio chassis.
The R79 checks 10k un-soldered.
I think that covers it.
I will have to do a little research and see if that could have been changed by Philco.
HAve a great evening guy's
murf

Maybe they changed to a single resistor of the proper value.

murf,

10k sounds pretty close to the correct value.

You might put everything back and check voltages.

Measure the voltage at each end of the suspect resistor while you wait for the problem to occur. Does either voltage change then?

Ted