Topics

Resistor wattage

N7QL
 

What wattage resistors should I use to build the Bitx 20? I thought I saw the value of 1/2 watt thrown about somewhere but I cannot find it. I will be ordering the parts Monday that I don't already have so I am trying to be sure before I do any ordering. Thank you.

Jerry Gaffke
 

The Bitx40 shipped by hfsignals is using all surface mount 1206 resistors, which are good for 1/4 Watt.
There are occasional reports of R141 burning up, the 10 ohm emitter resistor in the power amp driver,
so that one could be upped to 1/2 Watt (or two 20 ohm 1/4 Watt resistors in parallel)

Jerry, KE7ER


On Sat, Apr 27, 2019 at 06:55 PM, N7QL wrote:
What wattage resistors should I use to build the Bitx 20? I thought I saw the value of 1/2 watt thrown about somewhere but I cannot find it. I will be ordering the parts Monday that I don't already have so I am trying to be sure before I do any ordering. Thank you.

MVS Sarma
 

While homebrewing Sunil's bitx 20 or any other older version with through hole components , can better use quarter watt mfr and preferably mlc capacitors.

Sarma vu3zmv

On Sun, 28 Apr 2019, 7:35 am Jerry Gaffke via Groups.Io <jgaffke=yahoo.com@groups.io wrote:
The Bitx40 shipped by hfsignals is using all surface mount 1206 resistors, which are good for 1/4 Watt.
There are occasional reports of R141 burning up, the 10 ohm emitter resistor in the power amp driver,
so that one could be upped to 1/2 Watt (or two 20 ohm 1/4 Watt resistors in parallel)

Jerry, KE7ER

On Sat, Apr 27, 2019 at 06:55 PM, N7QL wrote:
What wattage resistors should I use to build the Bitx 20? I thought I saw the value of 1/2 watt thrown about somewhere but I cannot find it. I will be ordering the parts Monday that I don't already have so I am trying to be sure before I do any ordering. Thank you.

Adrian Chadd
 

is replacing that resistor a common mod for the bitx40?


-a


On Sat, 27 Apr 2019 at 20:39, MVS Sarma <mvssarma@...> wrote:
While homebrewing Sunil's bitx 20 or any other older version with through hole components , can better use quarter watt mfr and preferably mlc capacitors.

Sarma vu3zmv

On Sun, 28 Apr 2019, 7:35 am Jerry Gaffke via Groups.Io <jgaffke=yahoo.com@groups.io wrote:
The Bitx40 shipped by hfsignals is using all surface mount 1206 resistors, which are good for 1/4 Watt.
There are occasional reports of R141 burning up, the 10 ohm emitter resistor in the power amp driver,
so that one could be upped to 1/2 Watt (or two 20 ohm 1/4 Watt resistors in parallel)

Jerry, KE7ER

On Sat, Apr 27, 2019 at 06:55 PM, N7QL wrote:
What wattage resistors should I use to build the Bitx 20? I thought I saw the value of 1/2 watt thrown about somewhere but I cannot find it. I will be ordering the parts Monday that I don't already have so I am trying to be sure before I do any ordering. Thank you.

N7QL
 

Thank you! Yeah with not the best vision I prefer through hole. 

Jerry Gaffke
 

I doubt very many Bitx40's have had R141 replaced,
only a few have reported this part to have failed.
Operating above 12.0v will improve your chances of seeing a failure here.

Another part that is dissipating more than it should is Q13, 
replacing it with a through hole (not surface mount) 2n3904 
should be sufficient.

Jerry, KE7ER


On Sat, Apr 27, 2019 at 09:02 PM, Adrian Chadd wrote:
is replacing that resistor a common mod for the bitx40?
 

 

Jerry,

The R141 fails because of the 2219 near by. The ambient temperature
for R141 is made very high by the power transistor and a little more
dissipation causes it to fail.

The big blue round is 2N2219A directly south is R143 and slightly to the
left is R150. R141 is to the right of R143. If the TX is pressed long enough
the whole area turns red hot!

Emacs!

Raj


At 28/04/2019, you wrote:
I doubt very many Bitx40's have had R141 replaced,
only a few have reported this part to have failed.
Operating above 12.0v will improve your chances of seeing a failure here.

Another part that is dissipating more than it should is Q13,
replacing it with a through hole (not surface mount) 2n3904
should be sufficient.

Jerry, KE7ER


On Sat, Apr 27, 2019 at 09:02 PM, Adrian Chadd wrote:
is replacing that resistor a common mod for the bitx40?