I built my Ten-Tec Model 1202 Dual Band (HF/VHF) SWR/Power meter. It looks great and works well, on Forward Power...... On Reverse and on the SWR setting it reads very high (almost as much as forward power).
I've checked all of my solder joints, and I can find nothing wrong so I suspect I may have a bad component. Would anybody have any idea where to start?
There is a very poor scan of the schematic here: http://74.220.205.254/files/1202%20Manual.PDF It is located on page 5.
Thanks in advance.
"One man with courage makes a majority." ~ Andrew Jackson
Steve KA9MOT
Macomb, IL
My first gut hunch would be to check the polarity of the diodes, and then make sure you read the resistor colors right. Some times, the orange and red look close, as well as the blue and green. Of course the obligatory solder bridges should be checked for. Just a quick guess without looking at the schematic as I'm on the way out. Please post what you find, and good luck.
Last edited by K7SGJ; 06-13-2012 at 12:55 PM.
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I'm assuming you have the device connected to a reasonable load, or antenna, and you aren't really getting almost 100% reflected power. :)
Do you get the same odd results on both the HF and VHF sections of the device? The HF and VHF sections of the schematic look to be fairly independent. If one section is working properly, you can narrow down the problem considerably.
I have triple dog checked the polarity of the diodes. Double checked them before I soldered them. It is connected to my dummy load. I have not checked the VHF side as I do not have a 2M rig...... maybe I can get my buddy Scott KC9SIW to bring his by. And they are separated on the main board, but combines on the switch board.
Last edited by KA9MOT; 06-13-2012 at 03:41 PM.
"One man with courage makes a majority." ~ Andrew Jackson
Steve KA9MOT
Macomb, IL
If I wound the transformer wrong, would it cause this problem? I'm certain I wound it correctly and almost certain I soldered it to the mainboard correctly (INPUT vs. OUTPUT)
"One man with courage makes a majority." ~ Andrew Jackson
Steve KA9MOT
Macomb, IL
Did you check the diodes before you soldered them in? Not for polarity, but for open/shorts/voltage drop from anode to cathode?
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I have had the diode issue in an older antenna tuner.
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No.Originally Posted by N8YX
"One man with courage makes a majority." ~ Andrew Jackson
Steve KA9MOT
Macomb, IL
Do you have a digital voltmeter (or another high-impediance measuring instrument, like a VTVM) to take some DC voltage readings?
HF Forward Power measuring circuit
With the SWR/Power meter running and while transmitting:
1. What is the DC voltage at the cathode end (the banded side) of diode D3?
2. What is the DC voltage at pin 7 of U2a? (it should be about 1/2 the voltage measured in Step 1.)
HF Reverse Power measuring circuit
With the SWR/Power meter running and while transmitting at the same power level as above:
3. What is the DC voltage at the cathode end (the banded side) of diode D4?
4. What is the DC voltage at pin 1 of U2b? (it should be about 1/2 the voltage measured in Step 3.)
Ideally, the values from the reverse power DC readings should be much less than the values from the forward power DC readings if you are transmitting into a 50 Ohm load.
I'll check these items when I wake up. I got tied up today.
"One man with courage makes a majority." ~ Andrew Jackson
Steve KA9MOT
Macomb, IL
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