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QCX Blank LCD

Richard Hall NS3C All Messages By This Member #20775 Hello, I just built the 80 meter version of the QCX and have a blank LCD: no blocks, just the backlight. With 12.7 volts input I see these voltages at the LCD pins: 1 0 2 2.08 3 2.08 (varies with R47 from 0 to 2.08) 4 .03 5 0 6 0 7 2.08 8 2.08 9 2.08 10 2.08 11 2.08 12 2.08 13 2.08 14 0 15 4.52 16 0 Can you suggest where to start looking for the fault? Thanks, Richard NS3C
[email protected] #20779 Pin 2 of the LCD should have +5V on it.? Since it isn't there, the next logical place to look would be at the output of the +5V regulator.? With the numbers on the regulator facing you, what do you read on the right pin (using the center pin as ground)? Bill W2EB
[email protected] #20780 OOOOPS!? I just noticed you have nearly 5V at the backlight, so the regulator is probably working OK.? Check the solder connection of both the connector on the PCB and on the LCD module.? All OK?? Bill W2EB
Hans Summers All Messages By This Member #20781 Hi Bill The backlight is powered via a series resistor from 12V. So as to not increase the power dissipation of the 7805 regulator. So your original post is still valid? 73 Hans G0UPL? ? toggle quoted message Show quoted text On Jan 14, 2018 10:45 PM, <w2eb@...> wrote: OOOOPS!? I just noticed you have nearly 5V at the backlight, so the regulator is probably working OK.? Check the solder connection of both the connector on the PCB and on the LCD module.? All OK?? Bill W2EB
Richard Hall NS3C All Messages By This Member #20782 开云体育 Yes, I checked and reflowed the solders on both the PCB and the LCD. They seem OK. New problem: I had 2.8 volts between the pins of the regulator until I slipped and shorted them. That let a little smoke out and now I have .3 volts so I suppose I trashed IC11! Richard NS3C toggle quoted message Show quoted text On Jan 14, 2018, at 11:45 AM, w2eb@... wrote: OOOOPS!? I just noticed you have nearly 5V at the backlight, so the regulator is probably working OK.? Check the solder connection of both the connector on the PCB and on the LCD module.? All OK?? Bill W2EB
Richard Hall NS3C All Messages By This Member #20783 开云体育 I just ordered another 7805. To be continued… Richard NS3C toggle quoted message Show quoted text On Jan 14, 2018, at 11:53 AM, Richard Hall <n76003@...> wrote: Yes, I checked and reflowed the solders on both the PCB and the LCD. They seem OK. New problem: I had 2.8 volts between the pins of the regulator until I slipped and shorted them. That let a little smoke out and now I have .3 volts so I suppose I trashed IC11! Richard NS3C On Jan 14, 2018, at 11:45 AM,?w2eb@...?wrote: OOOOPS!? I just noticed you have nearly 5V at the backlight, so the regulator is probably working OK.? Check the solder connection of both the connector on the PCB and on the LCD module.? All OK??? Bill W2EB
Roger G4IUP All Messages By This Member #20784 Hi Richard, You have been unlucky if you have damaged the 7805 because it has internal short circuit protection. Does look like it is though!? 73 Roger G4IUP toggle quoted message Show quoted text On 14 Jan 2018 20:01, "Richard Hall" <n76003@...> wrote: I just ordered another 7805. To be continued… Richard NS3C On Jan 14, 2018, at 11:53 AM, Richard Hall <n76003@...> wrote: Yes, I checked and reflowed the solders on both the PCB and the LCD. They seem OK. New problem: I had 2.8 volts between the pins of the regulator until I slipped and shorted them. That let a little smoke out and now I have .3 volts so I suppose I trashed IC11! Richard NS3C On Jan 14, 2018, at 11:45 AM,?w2eb@...?wrote: OOOOPS!? I just noticed you have nearly 5V at the backlight, so the regulator is probably working OK.? Check the solder connection of both the connector on the PCB and on the LCD module.? All OK??? Bill W2EB
Stephen Farthing G0XAR JO92ON97 All Messages By This Member #20787 Possibly you haven’t installed the microcontroller correctly. Check for bent pins and correct orientation.? Regards, Steve
Bernd All Messages By This Member #20807 Hello Richard, remove the lcd component. how much volt is on R48 / PIN 15 LCD ?? does your power supply provide enough, or is it not designed for the load?
Richard Hall NS3C All Messages By This Member #20831 开云体育 Thanks, I’ll try that and report when I get the replacement for the 7805 I destroyed. Steve, I checked the micro controller: correct orientation and no bent pins. Thanks, everyone, for your help! Richard NS3C toggle quoted message Show quoted text On Jan 14, 2018, at 1:28 PM, bernd.treppmann@... wrote: Hello Richard, remove the lcd component. how much volt is on R48 / PIN 15 LCD ?? does your power supply provide enough, or is it not designed for the load?

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