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Still no output on QMX

 

When I first powered my QMX up, it came alive. However it had no output signal. I checked the finals and found one to be bad. I replaced it and tried again only to have the same final go bad. I checked it before installing it. At the suggestion of a fellow ham here, I rewound T501 for 12v instead of 9v I wound originally, I rewound L405A & 406B because I didn't like the way they looked. I also rewound T507 Swr transformer. I added transistor sockets for the finals and replaced the finals with new ones. I also checked Q507 and found it to be good. I powered it up and there is still no output power. I rechecked the finals and found all to be good. Can someone explain to me how to check IC507? Other than that, I have no clue why there is still no power output.?
 

Just my 2 cents.?
Replace all the BS-170s as a set. Now, when I build a kit, I install sockets for the PA transistors for just this reason. If not sockets, then some other way of mounting them to make it easier.? Some have never blown a single one,? I wish I could count myself as one of them.?
--
Wayne S.
KF7RCM
 

@?I added transistor sockets for the finals and replaced the finals with new ones.
?
I did.
 

?I have no clue why there is still no power output.
James,
how did you check the output, by the internal measurement or by an external?
?
For your tests use a good dummy load and a voltage of only around 7.5 V. The lower voltage could lower the chance of more damage.
?
  1. How much supply current when sending? Do you see a significant increase relative to receiving?
  2. Check terminal - Diagnostics - PA voltage (right side lower half of screen). How much when no key is pressed and how much when pressing "P" and later "T"?
?
73, Ludwig
 

well, I tested the best I could, with the knowledge and equipment I have.?
A list of my findings:
All testing was done with a dummy load rated at 4.97Ohms.
?
Idle current .104
keyed current .120
?
all 4 finals showed 0V at Idle and 2.47V at the drain when keyed.?
Putting the test lead on pin one, source, the output audio increased a lot.
?
the pinout voltages on the IC503:
?
? ?Idle? ? ? ? ? ? keyed
?
1? 0? ? ? ? ? ? ? ?1.621? ? ? ? ? ? ? ?
2? 0? ? ? ? ? ? ? ?3.28
3? 0? ? ? ? ? ? ? ?2.495
4? 0? ? ? ? ? ? ? ?1.621
5? 0? ? ? ? ? ? ? ?3.28
6? 0? ? ? ? ? ? ? ?2.494
7? 0? ? ? ? ? ? ? ?0
8? 0? ? ? ? ? ? ? ?2.487
9? 3.3? ? ? ? ? ? 1.611
10? 0? ? ? ? ? ? ?3.28
11? 0? ? ? ? ? ? ?2.48
12? 3.3? ? ? ? ? 1.612
13? 0? ? ? ? ? ? ?3.28
14? 4.97? ? ? ? 4.96
?
As far as your #2 bullett, I have no idea what you are talking about. Can you please explain?
Thank you for your time helping me. I was very disappointed that I couldn't use it yesterday, Labor Day. The replacement finals didn't arrive until today.
de James
 

On Wed, Sep 4, 2024 at 05:42 AM, James wrote:
4.97Ohms.
James, this may kill the QMX. The nominal value is 50 Ohm.
?
Idle current .104
keyed current .120
Much to low for TX. It looks like PA doesn't work, only driver (or maybe the PA a tiny bit).
?
all 4 finals showed 0V at Idle and 2.47V at the drain when keyed.
See above. More about this down in this post.
?
the pinout voltages on the IC503:
All values are ok.
?
The replacement finals didn't arrive until today.
In the moment I'm not sure about broken BS170. Please don't remove the current FET in the moment.
?
As far as your #2 bullett, I have no idea what you are talking about. Can you please explain?
Terminal access gives a powerful tool for diagnostics, debugging and configuration. Please read the operation manual (Terminal applications).
?
Please go to Hardware tests - Diagnostics and make screen shots for no key depressed, key "P" depressed and key "T" depressed. Maybe looking at these screen shots I can tell you more about the situation.
?
73, Ludwig
?
 

OMG I meant 49.7 OHMS So Sorry about that. LOL
 

My computer doesn't recognise the QMX. I've factory reset, but still gives an error when plugging it into the computer. well, it doesn't do anything when plugged into the usb and then turning the QMX on. Onay after I unplug the USB and then Plug it in while the QMX is already powered on, does it give an error message, but that is normal when you try to connect to the USB when the equipment is already powered on.?
?
I've built about 30-35 kits over the years, and this is only the third kit I've had problems with. This was built under a microscope so I'm pretty sure about the solder joints and that all the SMD parts are accounted for.
 

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Are you applying power (12V) and turning it on before plugging it in??

Also, IIRC, the USB negotiation only happens once after power on. So if you unplug & re-plug without a power cycle in between, the USB won't reconnect properly...

(I may not have all the details straight, but I think "Don't unplug & re-plug without intervening power cycle & power on" is correct!)

73, Paul -- AI7JR

On 9/4/24 15:11, James via groups.io wrote:
My computer doesn't recognise the QMX. I've factory reset, but still gives an error when plugging it into the computer. well, it doesn't do anything when plugged into the usb and then turning the QMX on. Onay after I unplug the USB and then Plug it in while the QMX is already powered on, does it give an error message, but that is normal when you try to connect to the USB when the equipment is already powered on.?
?
I've built about 30-35 kits over the years, and this is only the third kit I've had problems with. This was built under a microscope so I'm pretty sure about the solder joints and that all the SMD parts are accounted for.
-- 
Paul -- AI7JR
 

You are correct. you must plug into the USB port BEFORE powering on the device. Otherwise no handshake.?
 

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So, plug in USB when off, and then turn it on? That's not what I described, but it's easier to understand!

73

On 9/4/24 20:44, James via groups.io wrote:
You are correct. you must plug into the USB port BEFORE powering on the device. Otherwise no handshake.?
-- 
Paul -- AI7JR
 

I have officially given up on this kit. I will order another and try again in two months when I've saved enough out of my tiny government check, and try again. Thanks too everyone that tried to help me.?
?
de James
 

Might want to get ahold of Samantha. She just posted that she would like another project. Might be able to take a crack at it.
--
Wayne S.
KF7RCM
 

I have no idea who Samantha is.?
 

Okay, I've decided NOT to quit this project. But I'll need some help. First I will read ALL the other post which indicate similar problems that I am encountering. Has anyone mapped out some extra test points, voltage and/or RF points I can check? I have an oscilloscope, but I really don't know how to use it very well. I also have a voltage injection and a thermal camera to find shorts,? DMM, frequency counter, capacitor meter, induction meter, and a transistor tester. What more do I need?? Knowledge on how to use all this equipment past the introductory stages. More than willing to learn, I'm just overwhelmed at the moment. Thanks in advance,
?
James
 

On Wed, Sep 4, 2024 at 01:30 PM, @Ludwig_DH8WN wrote:
Please go to Hardware tests - Diagnostics and make screen shots for no key depressed, key "P" depressed and key "T" depressed. Maybe looking at these screen shots I can tell you more about the situation.
James,
these screen shots may help.
?
73, Ludwig
 

Hi Ludwig, I don't know if you got the message that my computer doesn't recognize the QRX at all. This afternoon, I will try to put it into the "Update firmware" condition and see if it will take reloading the firmware. If it does and I'm able to connect to my computer, I will post those screenshots you are asking for. Thank you for helping me overcome my discouragement.
?
James
 

Sorry, QMX!!
?
 

On Tue, Sep 10, 2024 at 08:34 PM, James wrote:
Hi Ludwig, I don't know if you got the message that my computer doesn't recognize the QRX at all.
James, I saw this message. Some later discussion made the impression this problem was solved.
The terminal access is importand for your problem. Which OS did you use on your PC?
?
73, Ludwig
 

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