Topics

Bad news #40m

Joe Cotton
 

All
I blew out the finals on my cue CX 40. I tried replacing all the transistors but apparently did not work. looking went to the QC x site wanting to buy a replacement kit.  the bad news is that hands changed the kit and now it will not fit in my enclosure I thought I could buy a new kit and just drop it in the same enclosure.
does anyone have a kit or even a completed unit that they would be willing to sell me.?
--
73, Joe Cotton, W3TTT

ajparent1/KB1GMX
 

So buy replacement parts.

Careful when extracting the old ones.

Allison
-------------------------------
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Trystan G0KAY
 

Joe,

Sorry to hear that you've blown the finals. Fear not, I've blown mine on two occasions now. On both times was when I had put it into WSPR mode and there was no antenna connected. 

The fact that I did it on two occasions show that I am consistently stupid. At least consistency is a virtue. 

Fear not then Joe! Tell us what parts you have replaced so far, and what you can hear when you try and receive. If you give us as much information as you can think of I'm sure the group can help you get back on air again with your QCX. 

Trystan
G0KAY

Ham Radio
 

You might want to consider using these Chinese current and voltage limit device in your shop.  These are inexpensive.
I put two in a homemade  case. Works great and current limit capability prevents “magic smoke”


--
73, Bernie, VE3FWF

Trystan G0KAY
 

Bernie,

That looks interesting. I think your post has gone onto the wrong topic?

A current limiter won't stop popping the finals when there is no antenna connected, or fix a broken QCX.

I'm guessing you're replying to a different post?

Trystan

Ham Radio
 

More from a troubleshooting aid point-of-view  as components are being replaced when doing a repair. 
--
73, Bernie, VE3FWF

Joe Cotton
 

I got some help from Ron WA7GIL.
Thanks for talking to me.  You gave me much insight to the rig.
Here are some of the results.
 
IC3 pin 3 and 4 - nice square wave at 7.0 MHz, but with a spike at the front.  See image.  So IC3 seems to be working normally. 
Q6 - zero volts with key up and down.  problem here.  R41 also zero volts.  
 
Therefore, I think I have an open circuit to the emitter of Q6.  I will check tomorrow or maybe Sunday. 

Well, after tracing down with more effort, I found that the 12v trace to Q1,2,3 was broken, as was a trace to Q4.  After I connected jumpers to these points, the radio came back to life!

 
--
73, Joe Cotton, W3TTT

ajparent1/KB1GMX
 

One thign I see repeated is the new QCX+ is something unlike the old QCX.

NEWS FLASH other than the board its completely the same radio.

That means everything that went into the old QCX is the same in the new
QCX so replacements are possible.  However the parts used are not obscure
or hard to obtain from many sources.
 
Hans did not abandon the QCX, he improved it for ease of assembly and
access to parts on the board and cooling of the BS170s.

Allson
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ajparent1/KB1GMX
 

The spike on the leading edge is your scope or probe.
IF you using a long ground clip that may be part of it too.

If the BS170s died it can and will sometimes take out Q6.

Allison
-------------------------------
Please reply on list so we can share.
No private email, it goes to a bit bucket due address harvesting

Ronald Taylor
 

Congratulations Joe. Glad you got it working. 

73... Ron 

On Wed, Jun 17, 2020 at 16:48 Joe Cotton <cottonj@...> wrote:
I got some help from Ron WA7GIL.
Thanks for talking to me.  You gave me much insight to the rig.
Here are some of the results.
 
IC3 pin 3 and 4 - nice square wave at 7.0 MHz, but with a spike at the front.  See image.  So IC3 seems to be working normally. 
Q6 - zero volts with key up and down.  problem here.  R41 also zero volts.  
 
Therefore, I think I have an open circuit to the emitter of Q6.  I will check tomorrow or maybe Sunday. 

Well, after tracing down with more effort, I found that the 12v trace to Q1,2,3 was broken, as was a trace to Q4.  After I connected jumpers to these points, the radio came back to life!

 
--
73, Joe Cotton, W3TTT