qcx+ resistor r35 #qcxp40 #missing


Yannig - F4IUJ
 

I have resistor R35 missing, it is supposed to be 750k and in my personal stash I only have a 680k or 1M.
Can somebody tell me if 680k is close enough! Do I need to do somehow 680. + 68 = 748?


Ronald Taylor
 

That resistor provides bias to IC9A from the 5 volt line to pin 3 of IC9. 648 ohms will probably work fine. Just measure the voltage on pins 1,2&3 of IC9 with an outboard DVM. They should all be between 4.5 and 5 volts. Typically 4.8 or so. Good luck. 

Ron

On Fri, Apr 30, 2021 at 14:57 YannigR via groups.io <yannig.robert=laposte.net@groups.io> wrote:
I have resistor R35 missing, it is supposed to be 750k and in my personal stash I only have a 680k or 1M.
Can somebody tell me if 680k is close enough! Do I need to do somehow 680. + 68 = 748?


G3SPL
 

R35 is part of the high pass for the CW filter. I think it would be wise to try 2 resistors in series as you suggest to make up a value reasonably close to 750K. If its value was not important, I guess the CW filter designer would have used the more common 680K resistor value, so best to get as close as you can with 2 resistors.
--
Peter Lee
G3SPL


Ronald Taylor
 

I stand corrected. Peter is correct. I was only looking at it from a DC perspective. Probably best to series the two to get closer to 750K 

Ron

On Fri, Apr 30, 2021 at 16:14 G3SPL <leepd60@...> wrote:
R35 is part of the high pass for the CW filter. I think it would be wise to try 2 resistors in series as you suggest to make up a value reasonably close to 750K. If its value was not important, I guess the CW filter designer would have used the more common 680K resistor value, so best to get as close as you can with 2 resistors.
--
Peter Lee
G3SPL


Yannig - F4IUJ
 

On Sat, May 1, 2021 at 01:14 AM, G3SPL wrote:
R35 is part of the high pass for the CW filter. I think it would be wise to try 2 resistors in series as you suggest to make up a value reasonably close to 750K. If its value was not important, I guess the CW filter designer would have used the more common 680K resistor value, so best to get as close as you can with 2 resistors.
Thank you,

I am a bit of a beginner, how do you it ? Just slide each resistor in a hole then solder together the other side ?

Yannig - F4IUJ


Ronald Taylor
 

That works. Just put one end of each resistor in each of the two holes and connect the other ends of both resistors together. 

Ron

On Sat, May 1, 2021 at 13:49 YannigR via groups.io <yannig.robert=laposte.net@groups.io> wrote:
On Sat, May 1, 2021 at 01:14 AM, G3SPL wrote:
R35 is part of the high pass for the CW filter. I think it would be wise to try 2 resistors in series as you suggest to make up a value reasonably close to 750K. If its value was not important, I guess the CW filter designer would have used the more common 680K resistor value, so best to get as close as you can with 2 resistors.
Thank you,

I am a bit of a beginner, how do you it ? Just slide each resistor in a hole then solder together the other side ?

Yannig - F4IUJ


Yannig - F4IUJ
 

Hello all,

At the end resistor R35 is not missing, it was just in a bag where I didn't notice it, so making the initial inventory was definitely not a waste of time as I would have never found it otherwise!

Anyway, thank you for the help.

73
Yannig - F4IUJ