开云体育

I'm just finishing up my build on a QCX+ 20m.
On page 52 of the assembly manual it mentions R50, the 270 ohm resistor being "larger than the other resistors" obviously a higher wattage rating.
... but the one provided in the kit looks exactly like all the others, (1/4w?).. same with the 270ohm R48 on the front panel..

Maybe this is a leftover comment from a previous rev of the manual?

??

On Tue, Jul 18, 2023 at 06:08 PM, Ronald Taylor wrote:

Hi Glenn. What revision?is your QCX+? My older Rev 2 still used the 1/4 watt resistor at R48. It was increased to 1/2 watt somewhere in the later revisions. If your kit is older you might refer to the instructions for the revision you have. But, R48 was indeed increased in size (ie Heat Dissipation) in later revisions as it runs a little hot.

?

Having said that, My Rev 2 QCX+ has been running with the smaller wattage resistor for a long time and shows no discoloration to the resistor or the surrounding board area. I'm sure you are fine using it. If you have a 1/2 watt one in your junk box, it won't hurt anything to substitute it.?

?Yes that R48 resistor is the feed to the display backlight LED.? Depending on what supply you are using, there is 10V or more across the 270 ohm resistor which will dissipate around 0.4W (depending on the actual supply voltage).? ?I found that the backlight was very bright so I replaced R48 with a higher value (I think maybe 390 ohm) which gives a more suitable brightness for my needs and reduces the power dissipation to just over 0.25W.
--
Peter Lee
G3SPL

R48 seems to be set for wow factor but using higher supply voltages it is too bright and on typical 2led illuminated panels is probably giving the LEDs a hard time if it’s on a lot. ?

On my QCX+5W I messed around with this for a bit and found 1.5K was fine indoors even on a 9V supply?

My QCX+ is the latest rev, 4? Just finished the build. I'll post comments on my thread "my QCX+ build" later today...

Yes, I noticed when I powered up, the LED backlight that you can see on the side of the display was extremely bright, I'll change r48 and see how it looks... is that just R48? not also R50?

Thanks Ron....gonna change it now