Model 80 jr resistors getting hot - Printable Version
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RE: Model 80 jr resistors getting hot - Xolo100 - 01-04-2021
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?
RE: Model 80 jr resistors getting hot - RodB - 01-04-2021
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.
RE: Model 80 jr resistors getting hot - Xolo100 - 01-04-2021
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.
RE: Model 80 jr resistors getting hot - morzh - 01-04-2021
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.
RE: Model 80 jr resistors getting hot - Xolo100 - 01-04-2021
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.
RE: Model 80 jr resistors getting hot - Xolo100 - 01-04-2021
I observe the max temperature of 90° c after letting the radio run for about 30 to 40 minutes to stabilize.
RE: Model 80 jr resistors getting hot - morzh - 01-04-2021
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.
RE: Model 80 jr resistors getting hot - Xolo100 - 01-04-2021
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.
RE: Model 80 jr resistors getting hot - Xolo100 - 04-23-2021
Just an update here's the finished radio and it works beautifully. Thanks for all the help from the forum.
RE: Model 80 jr resistors getting hot - Radioroslyn - 04-23-2021
You might want to flip the knobs around the other way around.
RE: Model 80 jr resistors getting hot - Paul Philco322 - 04-23-2021
Nice Philco. nice Stromberg.............enjoy.
Paul
RE: Model 80 jr resistors getting hot - Xolo100 - 04-23-2021
Thank you lol I didn't realize I did that here's the fix knobs are on correct now.
RE: Model 80 jr resistors getting hot - morzh - 04-23-2021
It's one of those moments....you realize something's wrong but cannot quite tell.
Like one of those pictures where the guy is upside don but his mouth is not.
