Hi Guys

can you give me some help i have popped R141 ,whilst working a station near Inverness who gave me 5/8/9 ,

Then Smoke !! luckily R141 let go ,

I would like to replace with a bigger value Resister by drilling 2 holes through the board to support the Resister with solder..

My question is : is the b40 board single or double printed circuit, my unit is shoehorned into its cabinet i don't want to pull it all out to find out ,

and don't want to do any more damage,

--
Regards John 2E0Eii

开云体育

Thanks Marco for your reply a big help

Hi John,

It is a double sided board.

I would just remove the resistor and put in a 1/2 watt in its place.? Also, check the transistor (Q14) to make sure it didnt sacrifice itself also.

Good luck

Marco - KG5PRT

On Thu, Feb 15, 2018 at 4:02 PM, John 2e0eii <2e0eii@...> wrote:

Hi Guys

can you give me some help i have popped R141 ,whilst working a station near Inverness who gave me 5/8/9 ,

Then Smoke !! luckily R141 let go ,

I would like to replace with a bigger value Resister by drilling 2 holes through the board to support the Resister with solder..

My question is : is the b40 board single or double printed circuit, my unit is shoehorned into its cabinet i don't want to pull it all out to find out ,

and don't want to do any more damage,

--
Regards John 2E0Eii

-- 
Regards John 2E0Eii

开云体育

Thanks for your help Chris and your feed back,

Un solder the smc resistor and fit a higher wattage resistor to the top of the PC it will do the job chris g0wfh?

On 15 Feb 2018 22:02, "John 2e0eii" <2e0eii@...> wrote:

Hi Guys

can you give me some help i have popped R141 ,whilst working a station near Inverness who gave me 5/8/9 ,

Then Smoke !! luckily R141 let go ,

I would like to replace with a bigger value Resister by drilling 2 holes through the board to support the Resister with solder..

My question is : is the b40 board single or double printed circuit, my unit is shoehorned into its cabinet i don't want to pull it all out to find out ,

and don't want to do any more damage,

--
Regards John 2E0Eii

-- 
Regards John 2E0Eii

I have just finished chasing the smoking R141. Even after replacing the smd with an axial 1/2 watt, mounted vertically, it continued to get blazing hot after only 2-3 seconds of PTT. Be sure to check to see if it's still getting hot. After checking the obvious, rechecking all resistor values, double checking transistor voltages using Randy's chart. After replacing Q14, I still had the problem. I removed R14 again and mounted a new one, elevated like a 3 legged bug. Problem solved. My conclusion, with Q14 mounted tight to the board, there is a risk that the metal Q14 case will short to the board. An insulated spacer should be used or have been used, to keep this device up just a bit from the board. A friend suggested cutting the bottom of my case to access to the entire underside of the board. A great idea for new builders. BTW, I mounted the axial 10 ohm resistor through the tiny hole near it's original location. That connects to the bottom board foil ground, and one of my smd pads were destroyed from unsoldering the burned R141.?

Sent from Mike's iPad WA1MAD

Mike,

Mesure the voltage across the resistors and you know the resistors value. Calculate :if I remember right V2/R = Voltage squared divided by resistance to get the power dissipated. That should give you some insight on why the Rs are getting hot.

Raj

At 16/02/2018, you wrote:

I have just finished chasing the smoking R141. Even after replacing the smd with an axial 1/2 watt, mounted vertically, it continued to get blazing hot after only 2-3 seconds of PTT. Be sure to check to see if it's still getting hot. After checking the obvious, rechecking all resistor values, double checking transistor voltages using Randy's chart. After replacing Q14, I still had the problem. I removed R14 again and mounted a new one, elevated like a 3 legged bug. Problem solved. My conclusion, with Q14 mounted tight to the board, there is a risk that the metal Q14 case will short to the board. An insulated spacer should be used or have been used, to keep this device up just a bit from the board. A friend suggested cutting the bottom of my case to access to the entire underside of the board. A great idea for new builders. BTW, I mounted the axial 10 ohm resistor through the tiny hole near it's original location. That connects to the bottom board foil ground, and one of my smd pa

ds were destroyed from unsoldering the burned R141.

Sent from Mike's iPad WA1MAD

开云体育

Did you mean that you removed Q14 again, rather than R14, elevated like a 3 legged bug Mike? A metal cased transistor certainly could short to adjacent pads if f mounted flush to the pcb.

Bill