If Q5 has shorted as you put it then there will be next to no voltage on the drain because of the two 10 k dropper resistors on the way to that drain.

Many people operate the  PA from a separate PSU from the 12 V psu powering the Qcx mini . If that is so there is no guarantee the grounds are at the same ground 
or even that the  PA 's PSU os grounded at all.  If that ground is -2.4 V low with respect to the ground of the  MIni then that  Q5 mosfet would turn on... it all depends on contact resistances and so on because the two psus are nominally inter grounded via the key enable line plug  black wire.  (at the instant before it is plugged in of course they are not necessarily so ).  If you have a PSU for the PA which is a switcher you will often find that infact the ground connection betwen the two is the AC Neutral line and the earthing connection in your house wiring SB.  

THe US may not use the MEN system so  in that case I have not a clue how your house wiring neutral links and so on work. 


Measuring the  0 Volt  line of the Qcx and the PA when powered up and NOT connected with respect to a common known good earth like a copper piping system might show you if there are issues to look at.  In the worst case a zero volt strap between the respective PSUS will ensure continuity of the zero volt line (without the Amp enable cable being in place)  


Do yourself a favour and put  470R resistor in the  active line of that cable. I suggested this to someone else who had a completely different issue.  He ignored me an pulled the power on his PA while the Qcx was powered up and destroyed the Qcx.  I asked him why he ignored that advice  (he had an early revision Qcx mini with the suspect regulator).  His advice was  that he thought that was only for hot plug and hot unplug issues.  I asked him why puling the power on the PA with the Qcx connected was not a hot unplug......

 

 

Ok, I may have an issue with my cable. It's not apparently shielded very well. I scoped at the output of the board and got a slightly cleaner signal and a good decode. Still has a number of spikes when the signal switches. I'll try to solder a new cable and see if that helps. 

On Wed, Sep 1, 2021 at 01:26 PM, Mont Pierce KM6WT wrote:

On Wed, Sep 1, 2021 at 11:21 AM, Mont Pierce KM6WT wrote:

This is 5v logic, so you need to set your probe to 1x.  You should see 5V or 2.5V per division.

See pics on my previous post #68528 (click here).

My scope is showing 2V per division, and the pick signal is at 5V.

(wish my scope had serial data decoder...  Very Nice).


73
km6wt

 Thanks! So, my probe was on 10x. Changed it to 1x and modified the scale. New photo included below. Still, very noisy and no solid decode by the scope. Haven't cracked open the QCXmini to check IC2 yet.

I'm with the other Jim:   get the ceramic screwdriver set.  I bought mine from ebay, because if at all possible, I will not do business with Amazon.  (Most of you probably know why, if you don't know and would like to know, ask me.)  I saw a set of ceramic tweakers probably 40 or more years ago, but never found any for sale until recently.  The current set isn't as good as what used to be available, some of the tips aren't ground properly, some of the tips aren't set in the handle properly, and that sort of thing.  So what?  Buy two sets if you have to (I did).  I also bought a set for a friend who has a masters in Electrical Engineering, current knows little about RF, but wants to design and market radios.  So I thought I'd save him the trouble of either not knowing about ceramic tweakers, or knowing about them but not having any.  If he ever spends any significant mount of time with cheap plastic tweakers, he'll realize what a favor I did for him giving him this set.

Hi Christi and Zdenek, that sounds like a QCX party on 80 m next time.

Next weekend is Field Day time in SSB I will participate with a friend. FT 817 80 m Long Wire and 12AVQ for the higher bands.
I am curious to see how QRP will work in SSB. Using DL0EU as callsingn.

Colin, seeing you are in UK here is a suggestion/supplier 10pc kit.

https://cpc.farnell.com/duratool/1pk-a001/trim-tool-set-10pc/dp/TL04137


or

https://www.amazon.co.uk/Adjustment-Screwdriver-Trimmer-Driver-ENGINEER/dp/B001HQMVU8
https://www.amazon.co.uk/Fdit-Frequency-Screwdriver-Anti-static-Plastic/dp/B07DC56L5J/ref=pd_lpo_3

On Wed, Sep 1, 2021 at 11:21 AM, Mont Pierce KM6WT wrote:

This is 5v logic, so you need to set your probe to 1x.  You should see 5V or 2.5V per division.

See pics on my previous post #68528 (click here).

My scope is showing 2V per division, and the pick signal is at 5V.

(wish my scope had serial data decoder...  Very Nice).


73
km6wt

On Tue, Aug 31, 2021 at 10:40 PM, David Chenault wrote:

I've added photos. Any suggestions?

Very Nice Scope.

This is 5v logic, so you need to set your probe to 1x.  You should see 5V or 2.5V per division.

Your pic shows it's displaying 200mv per division.  That's what mine looks like if my probe is on 10x instead of 1x.


73
km6wt

On Tue, Aug 31, 2021 at 11:57 PM, Alan G4ZFQ wrote:

NaviTrack has that command built in but most of the other commands need it to be used like a terminal program.

It's a little easier than a terminal program.
The text entry box has the command prefix, you add the cmd#,parm1,parm2...  and hit send.
It calculates the checksum for you as it sends it out the serial port.



Before I got NaviTrack running, I created a few dos .txt files with commands and checksums.  Then I just copy a .txt file to the com port from the dos command prompt to send it.  This is actually a bit easier as I don't have to remember the command #s and what parameters to use... 

To calculate the checksum, I used the NMEA Checksum Calculator webpage (click here).

On my setups I am asked when I start the program which, I suppose, is the same as running as Administrator.

That's cool...   Mine does not prompt...  not sure why.  

I have seen no way of saving settings. I do not think a supercap will help, it loses baud rate settings if it is powered on and another seemingly unrelated command is sent.

Yes.  When I send command 115 to select GPS satellites only, it resets the baud rate back to 9600.  It's probably doing some kind of internal reset to clear out unselected satellite tracking data.


Thanks,
km6wt

US Link:
https://www.amazon.com/Yosooo-Adjustment-Frequency-Screwdriver-Anti-Static/dp/B07D79XTR6/ref=sr_1_5?
 
--
Julian, N4JO.

--
Julian, N4JO.

Thank you Peter and Mardy for the kind replies.

I suspect I do have something wrong in the electronics.  After I did my alignment, I inspected my soldering and discovered that I had a small sliver of solder stuck to the bottom of the circuit board in the sticky solder flux in the are we are talking about.  I suspect that a short may have occurred during my alignment.

I've reflowed all of my soldered connections and verified the traces in the suspect area.  With the unit powered up, I came up with the following voltages using a 13.4v supply:

Junction of D3 and D5 is 13.0v.
Q5 drain is 13.4v.
Anode of D5 is 13.4v
Anode of D3 is 13.4v.

I'm suspecting that Q5 may have been shorted.  Could that be the problem?

Tom Dostal
K0INN



 

Colin,

You need to find a SPRAGUE-GOODMAN GTT-7 tool.  No longer made by them, but available from several overseas suppliers.  I have one that I bought several years ago, works great!

72/73,

Jim, K8IQY

Hi Tom and all QCXrs on the mail reflector.
Don’t know if this suggestion will help or not, but here goes. When I transmitted using the 40 meter CQX+ with the 50 watt amp running at reduced power (fed with 12 volts) the amplified signal out was overpowering my receive audio. A friend suggested using a common mode choke on the feed line. That measure eliminated the problem completely. I was operating outside in the back yard with a Super Antenna vertical about 20 feet from the rig and three ground radials also fairly close to the rig. The choke was made with 4 turns of feedline and some snap on ferrites.
Mardy Eedson
VE3QEE