开云体育

We?just completed a 40 meter QCX build with my 13 year old grandson.We are stuck on step 1 "LCD contrast adjustment".? We are following the current Trouble Shooting page under "Digital Section"and are getting the resutts as listed under"LCD all Blocks or all Blanks".? R47 has the full 5 volt range, but adjustment moves from all blocks to all blanks and never any alpha or numeric characters on the display. We performed all other tests in that section and found all ok with 1 exception.? Pin 1 on the LCD is ground with pins 5 and 16 measured?at ground as well.? The guide leads me to beleive that pins 5 and 16 should not be at ground although they appear to be at ground on the schematic.I also need to say that when we first powered up the QCX, the DC supply was connected in reverse for at least a minute before?we caught it.? Youthful enthusiasm makes a few errors!!? Old guys simply miss them!!? I dont think this caused any harm as D3 seems do have done its' job,? but I would appreciate any thought on where else to look.

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Right now we are looking at the Si5351A Synthesizer chip IC1.? Using a loop, it appears that the pins on the crystal side of the chip are a bit curled and corroded, as oppposed?to ?the pins on the opposite side that are flat against the pcb and shiny.? So right now I am thinking a malfunction in IC1.? But Im not sure how to confirm it.I cannot put test leads on the chip and am unsure enough of its operation to know what to expect at any test point.? Any thoughts on how to determine if IC1 is good or bad?

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I installed the following mods

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*moved inductor L5 to between pins 20 & 7

*Installed 10K resistor ffrom Q5 drain to +12Volts

*added 6.8K resistor from wiper R7 to ground

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Any suggestions greatly appreciated.

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Ken

W4DU