Welcome Guest! Be sure you know and follow the Phorum Rules before posting. Thank you and Enjoy! (January 12) x

Thread Closed
Thread Rating:
  • 0 Vote(s) - 0 Average
  • 1
  • 2
  • 3
  • 4
  • 5

Model 80 jr resistors getting hot
#16

I found it interesting, because the 36 detector oscillator tube data shows 165 volts on the screen grid to cathode. But the note for the philco 80 says there's a correction. I tend to go with what you guys are saying because you have more experience with these radios.

Just wondering if I put a higher wattage 16K resistor in place of the one currently in the circuit would that help cool down that particular resistor? And with the higher wattage would that have an adverse effect , positive effect or or neutral effect on my detector oscillator tube?
#17

The heat dissipated is current squared times resistance. If that number is higher than the rating of the resistor then you run the risk of damaging it. So, if you need to dissipate two watts you should use at least a three watt resistor. If you use a bigger wattage it will still dissipate two watts.
#18

I’ve measured 165 V through the 16 K resistor I’m coming up with 10.3 mA and 1.7 W. The resistor is a 5 W resistor that I have installed. So I believe it should be OK. However this resistor is still very hot to the touch, And from what I’ve read in the thread most likely it’s because the resistor is smaller in size then original. Everything in the radio seems to be working fine and the performance is good and I’m receiving all stations across the band. The resistor doesn’t show any signs of burning. My plate voltage on the 36 oscillator detector tube is showing right on spec 245 V my screen grid voltage on the 36 oscillator tube is showing a little low 86.7 V. If I go by the Riders schematic it says the screen grid should be 165 V but when I look at the RCA receiving tube data sheet it says Max volts for the screen grid should be 90 V and then when I read that note above in the tread it says it should be somewhere around 80 V. So I’m a little confused. I’m inclined to think everything is fine.
#19

You could possibly measure the temperature of the resistor and then look in the datasheet. If the temperature is well under the limit, you do not have to worry. At least your dissipation looks to be 1/3 of the rating (at 165V).
If you want to put the PN of the resistor, I will look in the datasheet.

People who do not drink, do not smoke, do not eat red meat will one day feel really stupid lying there and dying from nothing.
#20

Thank you Morzh The part number is ROX5SSJ16K the manufacturer is TE I observed a max temperature of 90° c after about 30 to 40 minutes of letting the radio stabilize and temperature.


Attached Files Image(s)
   
#21

I observe the max temperature of 90° c after letting the radio run for about 30 to 40 minutes to stabilize.
#22

Which is well within the rated temperature which is up to 155C..

Also, up to the ambient of 70C there is no derating of the load.

This is indeed a very small resistor for a 5W-rated one. Mere 17.5mm x 6.5mm. So it will get hot.

But if TE connectivity says it is good, then it is good.

People who do not drink, do not smoke, do not eat red meat will one day feel really stupid lying there and dying from nothing.
#23

Thank you Morzh. I'm satisfied with the results and I really appreciate your help and guidance and knowledge. Now on to the restoration of the case. Looking forward to having this radio on my mantle.
#24

Just an update here's the finished radio and it works beautifully. Thanks for all the help from the forum.


Attached Files Image(s)
           
#25

You might want to flip the knobs around the other way around.

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
#26

Nice Philco. nice Stromberg.............enjoy.

Paul

Tubetalk1
#27

Thank you lol I didn't realize I did that here's the fix knobs are on correct now.


Attached Files Image(s)
   
#28

It's one of those moments....you realize something's wrong but cannot quite tell.

Icon_lol

Like one of those pictures where the guy is upside don but his mouth is not. Icon_smile

People who do not drink, do not smoke, do not eat red meat will one day feel really stupid lying there and dying from nothing.




Users browsing this thread: 1 Guest(s)
[-]
Recent Posts
An attempt to remove the Field Coil from a G speaker
Mike; I've only run into a speaker with an open filed coil twice, and they were on newer speakers from the 1940s. One ...Arran — 12:48 AM
An attempt to remove the Field Coil from a G speaker
Arran Yes, this is my plan for now and what do I got to lose, this is not even the speaker from this radio, but one o...morzh — 10:44 PM
An attempt to remove the Field Coil from a G speaker
Mike;  I would unwrap the field coil, and see if maybe there a break near one of the ends, like where the coil wire att...Arran — 10:23 PM
An attempt to remove the Field Coil from a G speaker
...and this is what I did. I fed a little LT into the screwholes with a small brush, and a little on the rim next to the...morzh — 09:52 PM
Philco 40-120C Restoration
I combined the two 40-120C threads together as we like to keep the discussion of the same radio together. It helps with...klondike98 — 09:36 PM
Philco 40-120C Weak, Distorted Ouput
Just checked were I buy tubes price is four dollars. So living in Florid we have a local source for tubes. David    David — 09:14 PM
Philco 40-120C Weak, Distorted Ouput
The higher voltage may be due to higher mains voltage. My mains run 120-125AC when the set was new mains would be 110-11...David — 09:09 PM
Philco 40-120C Weak, Distorted Ouput
Thank you for your reply. I pulled a speaker from a Philco 41-221 and received the same result. I used a signal tracer t...bluecap — 08:45 PM
Philco 40-120C Weak, Distorted Ouput
Have you tried a different speaker? How did you trace the distortion? How do you know it is weak? What is the reference?...morzh — 08:33 PM
Philco 46-480 Electronic Restoration
Amen to that! Every time I think I’ve captured them all, I realize that there’s another error. My goal is to finish with...jrblasde — 07:00 PM

[-]
Who's Online
There are currently 1940 online users. [Complete List]
» 1 Member(s) | 1939 Guest(s)
Avatar

>