Re: 40M QCX 14.8V on Voltage Regulator Output

James Daldry W4JED
 

Hi, Mike

Oh - is that why it's getting dark and I can only see my shoes? And said shoes are getting wet? And when I look up I can only see a round patch of sky? Thanks for the info. Uh, could somebody pass me a ladder?

73

Jim W4JED

On 5/25/19 9:47 AM, Mike wrote:
James,
When you realise that you are digging a hole for yourself, its generally a
good idea to stop digging.
But to realise that there is a hole requires knowledge

On 25 May 2019 at 9:22, James Daldry W4JED wrote:

Hi, Fred

I read the symptom description and looked at the picture. I know it's
highly unlikely that there's anything major wrong. My first guess is to
look at the microprocessor socket and make sure that all the pins went
into the socket, that one isn't outside the socket or buckled. Not only
been and done, but proudly wear the T-shirt. BUT-

The fact that our intrepid Tech managed to read a negative voltage in a
system with only 1, positive, power supply indicates to me that he
probably couldn't get light out of a flashlight bulb, a piece of wire,
and a "D" cell. This is not intended as a put-down. We aren't taught
this stuff in school.  To trouble-shoot a circuit you first have to know
what a circuit is. I've had, on multiple occasions, to fix the results
of someone without quite enough skill attempting a repair. The things
that make this an amazingly high-performance radio in a little package
make it an amazingly difficult thing to repair without half destroying
the board. You could write a book on how to trouble-shoot and repair it.
Our Tech doesn't own that book.

So - getting a person that has a job, that has to eat and sleep,
probably has to interact with family, and at the same time go from
square zero to apprentice electronic technician is going to take a
substantial amount of time. Probably years. In the process things will
get burnt by soldering equipment, parts will get hooked up wrong and
destroyed, probes will slip and gates punctured. That's life.

I just wanted to get an almost-a-radio converted into a radio in the
minimum amount of time, with minimum destruction.

Jim W4JED

On 5/24/19 8:11 PM, Fred Lodden wrote:
Jim,
You might want to tone it down a little.
The original poster has been licensed with a Technician class licence
for less than 20 days. He would be new to the hobby. On the steep part
of the learning curve. He does not have 50 years of tech experience
under his belt.
Got himself a low cost CW transceiver kit, put it together (probably
with great excitement) turned it on and did not see what he expected.
He seeks help from the group.
I find that his report of the issues was very good. A couple of photos
and some voltages from various parts of the circuit. So much more
information than many trouble reports provide.
I still think that there might not be any real big problem with the unit.
Perhaps it is just an unsoldered lead or a cold joint somewhere.
The fact that the LCD backlight comes on says that there is some
voltage somewhere, and it is not reverse polarity otherwise the LCD
backlight LED would not come on at all. From the photos the power
connections appear to be correct. Measuring voltages around the 7805
regulator (with reference to ground) will further help to diagnose any
issue.
I seriously hope that he is not deterred and persists with the
diagnosis, and the hobby.
73 Fred VK2EFL


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