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On 3/23/2024 07:27, Greg McCain via groups.io wrote:
> Well,
>
> I personally would carefully remove the cap and then check continuity
> between pins 1 and 2 at the LCD display itself.
>
> If it still shows a short, the problem is probably:,
> -- a bridge between? pins 1 and 2 of the LCD solder connections
> --? something in the LCD internals
> -- or possibly something off in the PAD resistor PAD circuit on the
> other end. There's a Vcc feed over there too.
>
> And of course, check the cap itself for a short once it's out of the
> circuit. If it is shorted, that's the culprit.
>
> Good luck. Not sure if you are comfortable with working like that on
> small SMDs.
>
> Greg
>
>
>
>
> Yahoo Mail: Search, Organize, Conquer
> <>
>
>? ? On Fri, Mar 22, 2024 at 11:41 PM, Al Simons
>? ? <al@...> wrote:
>? ? I pulled the trimmer this afternoon, and it shows ~22k as spec'd, and
>? ? the wiper goes smoothly over that range. I don't remember whether it
>? ? went all the way to zero at the ends or not, but I've put the wiper
>? ? mid-range in my testing and it doesn't change the apparent short
>? ? between
>? ? VCC and GND.
>
>? ? I have raised the black pin spacer blocks on JP303 and 304 to make
>? ? sure
>? ? there was nothing extraneous being hidden, but the board is clean.
>
>? ? I tried to pull the jumpers on display pins 1 and 2, to isolate the
>? ? problem to the display board or the carrier board that has the various
>? ? components on it, but I was unsuccessful on getting them unsoldered
>? ? enough to be able to pull the wires.
>
>? ? So of your list, I think we are down to a shorted C301, or a short on
>? ? the display board.? Any other ideas welcome!
>
>? ? Good night.
>? ? -Al
>
>? ? On 3/22/2024 18:59, Greg McCain via groups.io wrote:
>? ? > C301 sure looks like a bypass capacitor for the 5v feed into the LCD
>? ? > board. There to send little spikes and ripples on Vcc (the output of
>? ? > the 5V power supply) safely down the ground.
>? ? >
>? ? > One side of it should have continuity with pin 2 of JP303 (the four
>? ? > pin connector).
>? ? >
>? ? > The other side, I believe, should not show continuity with that
>? ? pin 2,
>? ? > when checked with an ohm meter.
>? ? > And of course, there should also not be continuity directly between
>? ? > the actual contact ends of the capacitor, unless perhaps . . .
>? ? >
>? ? > C301 is indeed shorted . . .
>? ? > OR There is a short between pins1 and 2 on the LCD component itself,
>? ? > OR there is a short through the trimmer resistor (R305)
>? ? > OR? if the trimmer resistor can actually be set to '0' ohms.
>? ? >
>? ? > Can you confirm that the trimmer resistor is? turned all the way
>? ? > counter-clockwise (when looking right down on the top of the
>? ? bugger)?
>? ? >
>? ? >
>? ? > Greg
>? ? >
>? ? > Greg McCain
>? ? > gamccain50@...
>? ? >
>? ? >
>? ? > On Friday, March 22, 2024 at 07:27:20 PM EDT, Al Simons
>? ? > <al@...> wrote:
>? ? >
>? ? >
>? ? > With the display board out of the radio, I measured 0 ohms
>? ? between pin 2
>? ? > of the 4 pin connector (GND), and the pad to the right side of C301,
>? ? > which is marked VCC on the trace diagram. Seems "odd." Possible
>? ? shorted
>? ? > C301? Unfortunately, I have no surface mount skills or equipment.
>? ? >
>? ? > What is a path forward?
>? ? >
>? ? > 73,
>? ? > -Al WA1TYB
>? ? >
>? ? > On 3/22/2024 15:44, Greg McCain via groups.io wrote:
>? ? > > Hopefully something simple and/or obvious.
>? ? > >
>? ? > > Don't forget to check the 2 header connectors on the main
>? ? board too.
>? ? > >
>? ? > > Good hunting. Let us know if you solve it.
>? ? > >
>? ? > > Greg KI4NVX
>? ? > >
>? ? > >
>? ? > >
>? ? > > Yahoo Mail: Search, Organize, Conquer
>? ? > >
>? ? >
>? ? <
>? ? <>
>? ? >
>? ? <
>? ? <>>>
>? ? > >
>? ? > >? ? On Fri, Mar 22, 2024 at 5:05 PM, Al Simons
>? ? > >? ? <al@...> wrote:
>? ? > >? ? Greg, THANK YOU.? Pulling the display board lets it come
>? ? up, drawing
>? ? > >? ? ~150mA at 6V. The terminal program is running, so it seems
>? ? that at
>? ? > >? ? least
>? ? > >? ? part of the CPU is OK.? Now to figure out what I did wrong
>? ? with the
>? ? > >? ? display board!
>? ? > >
>? ? > >? ? Again, thanks.
>? ? > >? ? -Al WA1TYB
>? ? > >
>? ? > >? ? On 3/22/2024 14:36, Greg McCain via groups.io wrote:
>? ? > >? ? > Just a quick thought.
>? ? > >? ? >
>? ? > >? ? > Without the control board will the unit even power up
>? ? since the
>? ? > >? ? rotary
>? ? > >? ? > push to power on won't be available?
>? ? > >? ? >
>? ? > >? ? > You might try just removing the display.
>? ? > >? ? > If the current stays up, then the fault might be in the
>? ? display
>? ? > >? ? board
>? ? > >? ? > or the 5v power board.
>? ? > >? ? >
>? ? > >? ? > I've seen other posts where faults/ bridges/shorts in the
>? ? power
>? ? > >? ? > boards' connector chains have caused odd problems. I took the
>? ? > advice
>? ? > >? ? > in the build instructions and clipped the one set of pins
>? ? back
>? ? > >? ? about a
>? ? > >? ? > millimeter or so because I could definitely see I that a few
>? ? > >? ? were too
>? ? > >? ? > long and extended past the solder pads and awful close to
>? ? other
>? ? > >? ? items.
>? ? > >? ? >
>? ? > >? ? >
>? ? > >? ? > Greg
>? ? > >? ? >
>? ? > >? ? >
>? ? > >? ? > Yahoo Mail: Search, Organize, Conquer
>? ? > >? ? >
>? ? > >
>? ? >
>? ? <
>? ? <>
>? ? >
>? ? <
>? ? <>>
>? ? > >
>? ? >
>? ? <
>? ? <>
>? ? >
>? ? <
>? ? <>>>>
>? ? > >? ? >
>? ? > >? ? >? ? On Fri, Mar 22, 2024 at 2:32 PM, Al Simons
>? ? > >? ? >? ? <al@...> wrote:
>? ? > >? ? >? ? Just completed my Rev 3 QMX assembly. It performs the
>? ? USB stick
>? ? > >? ? >? ? emulation ok, to place the FW file on board. I did
>? ? this both on
>? ? > >? ? >? ? initial power-up and by jumpering AUX2 to GND.
>? ? However, after FW
>? ? > >? ? >? ? load, when I press the left knob it draws power for an
>? ? > >? ? instant and
>? ? > >? ? >? ? then powers back down to 0.000A.? I'm using 7V, limited to
>? ? > 200mA.
>? ? > >? ? >? ? I have inspected all my joints w/ a magnifier, all
>? ? seem fine but
>? ? > >? ? >? ? I'm considering buying a USB microscope.
>? ? > >? ? >
>? ? > >? ? >? ? To start troubleshooting I want to check the power
>? ? boards.? For
>? ? > >? ? >? ? easier access, is it safe to power up the unit without the
>? ? > >? ? control
>? ? > >? ? >? ? board and display boards plugged in?
>? ? > >? ? >
>? ? > >? ? >? ? I've been monitoring this group since I placed my
>? ? order.? I
>? ? > think
>? ? > >? ? >? ? I remember a reference to a troubleshooting guide by
>? ? Hans, and
>? ? > >? ? >? ? another report of this failure mode, but I can't find
>? ? either.
>? ? > >? ? >? ? Pointers to either would be greatly appreciated. I'm aware
>? ? > of the
>? ? > >? ? >? ? troubleshooting log Hans has posted about units he's
>? ? fixed,
>? ? > >? ? but it
>? ? > >? ? >? ? doesn't mention this failure.
>? ? > >? ? >
>? ? > >? ? >? ? Thanks for any advice and pointers.
>? ? > >? ? >? ? 73,
>? ? > >? ? >? ? -Al WA1TYB
>? ? > >? ? >
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