R1 running hot

General discussion and support for the Peaberry SDR V2.

R1 running hot

Postby k1qn » Wed Jun 17, 2015 4:29 pm

I noticed that the big 22 ohm resistor, R1, is running hot to the touch. I know it's a 2 watt resistor, and I'm not leaving any skin on it, but just how hot is it supposed to run?
Al Gerheim, K1QN
Celebrating 50 years in ham radio!
k1qn
 
Posts: 90
Joined: Sun Oct 20, 2013 9:42 pm

Re: R1 running hot

Postby W4MMP » Wed Jun 17, 2015 4:45 pm

k1qn wrote:I noticed that the big 22 ohm resistor, R1, is running hot to the touch. I know it's a 2 watt resistor, and I'm not leaving any skin on it, but just how hot is it supposed to run?


Hi,
VERY hot. So hot that I can not touch it but for a very brief moment. Mine run about 42°C with a somewhat inaccurate IR thermometer. The 3V and 5V regulators run even hotter.
73
Ron / W4MMP
W4MMP
 
Posts: 579
Joined: Fri Jan 03, 2014 3:31 pm
Location: Lovettsville, Virginia FM19EG

Re: R1 running hot

Postby k1qn » Wed Jun 17, 2015 6:21 pm

The voltage drop is 4.82 volts, indicating a current of about 220ma, which is well within spec. Also indicates a dissipation of about 1 watt which is well within the 2 watt limit.

Suggestion: Instead of making a direct current measurement, measure the voltage drop across R1. (I'm an old EE Lab Instructor.)
Al Gerheim, K1QN
Celebrating 50 years in ham radio!
k1qn
 
Posts: 90
Joined: Sun Oct 20, 2013 9:42 pm

Re: R1 running hot

Postby W4MMP » Wed Jun 17, 2015 6:33 pm

W4MMP wrote:
k1qn wrote:I noticed that the big 22 ohm resistor, R1, is running hot to the touch. I know it's a 2 watt resistor, and I'm not leaving any skin on it, but just how hot is it supposed to run?


Hi,
VERY hot. So hot that I can not touch it but for a very brief moment. Mine run about 42°C with a somewhat inaccurate IR thermometer. The 3V and 5V regulators run even hotter.


Correction: It is the two 5V regulators that run hot. The 3V does not.
73
Ron / W4MMP
W4MMP
 
Posts: 579
Joined: Fri Jan 03, 2014 3:31 pm
Location: Lovettsville, Virginia FM19EG


Return to Peaberry SDR V2

Who is online

Users browsing this forum: No registered users and 2 guests

cron