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Author Topic: http://www.KitsAndParts.com CW kits.  (Read 644 times)

KH2BR

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http://www.KitsAndParts.com CW kits.
« on: January 03, 2021, 04:11:18 PM »

http://www.KitsAndParts.com CW kits.
Has anyone built the kits and parts dot com 5 watter cw rig?  I am using the 20 meter version and it is
suffering from low power output. 1.5 watts on 20 meters.  The drive is ok. In key down I can drive over 1 amp current for testing, then turn it down to 800 ma. at that point it is putting out 1.5 watts. The output of the driver is 7 volts peak to peak {collector of Q2 }. It is the same as my 40 meter rig. I figured that the lowpass filter could be the problem, so I took one turn off of each lowpass inductor but that did not fix the problem. I swapped out the finals and that did not fix it.  So, I am getting the required key done current but the output is low.
Someone has probably run into this problem. I hope to hear of what you found.  Robert KH2BR
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KZ1X

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Re: http://www.KitsAndParts.com CW kits.
« Reply #1 on: January 03, 2021, 05:31:45 PM »

Looks like a fun project, don't have one ... but I did go get the schematic.
I am a fairly experienced builder and maybe a second set of eyes can help.

Guess I can can ask the obvious questions and get away with it ...  ;-0

Any chance there's a mis-populated part?  For example, swapping C6 and C8 ?

Or a wrong value part at R1 or R2?

One of D3 or D4 backwards, or swapped with some other diode?

Then there is always the famous toroid-lead tinning problems in kits of this type.
If the center of the secondary on T2 isn't grounded....or one end of the secondary on T1...

Steve KZ1X
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N8NK

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    • N8NK QRP
Re: http://www.KitsAndParts.com CW kits.
« Reply #2 on: January 03, 2021, 09:16:40 PM »

Agreed with KZ1X. Another thought: you sound able to work your way through the schematic. You could assemble a quick RF voltage probe to be used with your DMM. All it takes is a diode (any type) and small cap (.01uf etc) and a resistor. The schematics are all over the placee. And in every Heathkit manual. That's a hint. Then you can step your way through the Tx chain, measuring RF voltages at the appropriate points (each stage input and output, including all filters and Tx mixer and associated band pass filter after the mixer.. altho I believe you said driver input level is right. If that's the case, mixer and BPF are working. Good luck OM
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K6SDW

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Re: http://www.KitsAndParts.com CW kits.
« Reply #3 on: January 03, 2021, 10:39:38 PM »

From QRpGuys I built their RF probe, cost $10 and about 30 minutes to assemble.

https://qrpguys.com/qrpguys-simple-rf-probe

They also sell their RF dummy load/Power Meter, cost $10 which I built and works much better for QRp power levels

https://qrpguys.com/12w-dummy-load-power-meter

GL
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KH2BR

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Re: http://www.KitsAndParts.com CW kits.
« Reply #4 on: January 06, 2021, 11:34:04 AM »

Problem solved !!  stupid operator error, discovered I was using a times 1 probe loading down the circuit. Switched to a times 10 prob and rig is actually putting out 6 watts. I spent days on this trying to fix a problem that did not exist.
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K3UIM

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Re: http://www.KitsAndParts.com CW kits.
« Reply #5 on: January 06, 2021, 06:55:55 PM »

BR: And I've been beating my head against the wall thinking I am the only one to do such a thing!!! LOL
Charlie
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Charlie. K3UIM
Where you are: I was!
Where I am: You will be!
So be nice to us old fogies!!

KX4OM

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Re: http://www.KitsAndParts.com CW kits.
« Reply #6 on: January 07, 2021, 12:05:32 AM »

A whole bunch of folks in the groups.io qrptec built those rigs as a group build effort a couple of years ago.

https://groups.io/g/qrptech/topics

You will get some help there, I am sure.

Ted, KX4OM
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KH2BR

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Re: http://www.KitsAndParts.com CW kits.
« Reply #7 on: January 07, 2021, 12:34:18 PM »

Thanks Ted, I just signed up !!
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