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#20m JP 3, 4, and 5 #20m


Syd
 

Just starting to test/align this rig. The display is all blacked out! Trying to see what is supplying the voltages and signals into the display module, I see that JP3, JP4, and JP5 are the connections to the display board and it sure would be nice to know what these three JP pins are connected to, especially the VDC and gnds!  I cannot find any place in the QCX+ manual that shows what is on these pins.  Is there a list of what is on these pins?
73 wt1v


J Ramos <joshramos@...>
 

Did you try adjusting the contrast pot for the LCD? Sections 6.1 and 6.2 in the manual have a few things to check that might solve what you’re seeing.

 

73

AE0CM


Evan Hand
 

Syd,
The pins are labeled on the schematic.  You will find JP5 between C21 and C22 above Q7, JP3 and JP4 are to the right of IC2.  I believe that is the only place that the jumpers are documented.

73
Evan
AC9TU


Steven Dick
 

The schematic on pages 149-150 of the manual shows signals on front panel JP1,2,3.  Not sure what you mean by "the display is truly black." Does the backlight light up?  If not, you have an open path to the LEDs in the LCD. Have you tried adjusting the contrast pot? You can test voltages at the top of the front panel pc board which go to pins 1-16 of the LCD. The LED ungrounded pin should have voltage on it and the contrast pot should move that voltage when you adjust it.  Most likely you have a bad solder joint on the front panel PCB or on one of the pins on front panel PCB JP1,2,3 or mating connectors on the main board especially on the ground pins.  It's difficult to probe these when the QCX+ is assembled but it's relatively easy to probe LCD signals at the top of the front panel PCB and trace them to their final source or destination at the processor. Probe very carefully to not short adjacent pins on the processor.

-Steve K1RF

------ Original Message ------
From: "Syd via groups.io" <nhuq1@...>
Sent: 9/17/2020 9:30:03 PM
Subject: [QRPLabs] #20m JP 3, 4, and 5

Just starting to test/align this rig. The display is all blacked out! Trying to see what is supplying the voltages and signals into the display module, I see that JP3, JP4, and JP5 are the connections to the display board and it sure would be nice to know what these three JP pins are connected to, especially the VDC and gnds!  I cannot find any place in the QCX+ manual that shows what is on these pins.  Is there a list of what is on these pins?
73 wt1v

Virus-free. www.avast.com


Syd
 

I have checked for the following:

there is 5 VDC on the LCD pin 2

there is 10 VDC on the LCD pin 15

I checked the gnd path from the main pcb to the pins on the LCD, it's there

I also checked the  pot output to the LCD and found an LCD pin 3 where the adjustable voltage on the pot matches the LCD

I can see the on/off switching voltage working at JP3 pin 3

so it's looking like I am going to unassemble the LCD bd assembly and look for mistakes on the assembly.

Finally, when I get the LCD pcb apart, can I apply a 5VDC directly to the LCD power pin 2 and a adjustable VDC on pin 3 to see if the LCD lights up?
If I get desperate it would be nice to affirm that the LCD actually works.

73 wt1v


Syd
 

by truly black I mean no display at all, no backlight or anything!


Evan Hand
 

Syd,
The backlight can fail and the display still works.  You need to have light to see the characters and adjust the contrast control.  You should at least be able to see some boxes.

Did you try adjusting the contrast control as AE0CM suggested?
73
Evan
AC9TU


Steven Dick
 

The LCD has two internal LEDs in series for the backlight. LCD pin 16 should be at ground. You can measure from LCD pin 16 to any convenient ground point on the main PC board.  That is also checking the interface connector as well as any bad or missing solder joints on the LCD and the connector path.  LCD pin 15 should be sitting at about 4.4 volts with a +12V power supply.  If it is sitting at 10V, that may indicate pin 16 is missing its ground.  When you say you checked the gnd path from the main pcb to the pins on the LCD, it's there, the one that's in question is pin 16, which is for the return current for the backlight LEDs.  Pin 1(VSS) and Pin 5 (RW) may have their grounds, but pin 16 is independent of these and should be checked by itself with an ohmmeter to the main board ground.

-Steve K1RF

------ Original Message ------
From: "Syd via groups.io" <nhuq1@...>
Sent: 9/18/2020 11:34:42 AM
Subject: Re: [QRPLabs] #20m JP 3, 4, and 5

I have checked for the following:

there is 5 VDC on the LCD pin 2

there is 10 VDC on the LCD pin 15

I checked the gnd path from the main pcb to the pins on the LCD, it's there

I also checked the  pot output to the LCD and found an LCD pin 3 where the adjustable voltage on the pot matches the LCD

I can see the on/off switching voltage working at JP3 pin 3

so it's looking like I am going to unassemble the LCD bd assembly and look for mistakes on the assembly.

Finally, when I get the LCD pcb apart, can I apply a 5VDC directly to the LCD power pin 2 and a adjustable VDC on pin 3 to see if the LCD lights up?
If I get desperate it would be nice to affirm that the LCD actually works.

73 wt1v

Virus-free. www.avast.com


Syd
 

problem solved! pin 16 on the LCD display was not making connection to the gnd. Resoldered, done!
73 wt1v