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Thanks Peter, I knew that lowering the impedance of the contrast control worked, but did not investigate why. Now I know. Thanks. 73 Vin

Just like mine peter. when transmitting, there was a few milli-volts change on the contrast pin. I modified the PCB by 1) replace the pot with a lower resistance say 5k pot. 2) Cut the track

Display contrasts in and out like it should, just no text. Only two rows of blocks. Fades away one end of the pot, back again at the other. Have checked continunity between IC2 and the display and its

Note that compared to operating a bs170 on 12 volts, excessive dissipation is reached at a much lower rf output at 5 volts. For one device, 300 mW is a good place to stop at 5 volt operation. If you

Thanks Shirley for your detailed suggestions! It is indeed the contrast, not the backlight that is flickering. The +5V rail remains stable during key down (4.830V key up, 4.832V key down, measured

Check voltage on pin 3 of display, with respect to the voltage on pin 1 (0volts). When mine was set up, it measured 0.9V and was extremely critical. If you turn the pot to the end-stop, both ways, and

Sorry to hear that Roger.. It gives you the excuse to upgrade to the U3S or QCX though Hi Hi. And also do some repairs to the bust kits. 73 James 2E0MUA

Using an AVR output for variable backlight control is a neat idea. But I think it's impossible to do on the QCX because there aren't any pins left - every I/O pin on the microcontroller is already in

LCD Display flicker and contrast change is something that can be evaluated with a simple test platform made up of an LCD and an Arduino. Run the "Hello World" program from Arduino IDE examples to get

Thanks, Michael Sounds like a plan Marc

Marc, The first time I ran through the process I thought the same thing...the variable capacitor had very little effect and the resistors barely dipped the display but I kept repeating the process

Nice tip Michael; I have been kit building for many years and I have been bending 'em up, one component at a time!? No wonder it takes me so long to build my kits!? Thanks for passing it along, Karl

Very helpful Greg - that saves a lot of time. Thank you for your advice.? 73 Brian G3ZOH

Flickering of the backlight brightness is caused by voltage drop in the +12 power supply rail. In the QCX design the LCD backlight is powered from the +12 rail through a resistor rather than from the

Cheers for the response Hans...I've not resolved the fact that when I change the side tone frequency my TX and RX frequencies are no longer aligned. I need to experiment a bit more to see if I can

Shirley, Appreciate the clarification.? Thank you for the speedy reply.? 73, Guy N7BIR

I noticed that the display contrast changes quite strongly (characters becoming dark) when transmitting, causing the display to flicker when sending CW. Is this a general problem, or is there

none of that was necessary, Brian. I have already used the same encoder for QRPLabs VFO/Signal Generator with no need for any additional circuitry. I just grabbed +5V from one of the pins of GPS

Hey Guys I went through the alignment procedure and it went strangely. BPF display bar was varying in strength?even before I started to turn the C1. It had a "8" when I went forward but it varied as

And it did, Hans :-(