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Hi all, I have run my U3 V3.03b with the AD9850 DDS for a long time without the GPS kit but now after having? fitted it to the U3 everything worked as it should but I have no power output anymore.

If I buy the new U3S will my U relay switch kit V2 work with it ?, any suggestions or advice would be? welcome.

Thank you. 73 Colin DD5CF / G1ZOS

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Hi Hans,
Thank you for your reply, I do not have an oscilloscope (I even had to look up the spelling) and have never been any good at fault finding (my wife would not agree) so I will buy the new version and give the old one away to someone with better test equipment than me, still it is a mystery why after all this time just connecting the GPS module would cause the RF output problem, could the chip have been damaged in some way by the GPS signal? I have tried changing the DDS and BS 170's and adjusted the blue pot on the DDS but still no joy even after removing the GPS module, I was really pleased to see the heart beat and correct time in the display for the first time.
73, Colin.

I do not have an oscilloscope

Colin,

There is a simple alternative to the 'scope for RF tracing.
A diode probe, for example And many other pages, the second down here the one with DC block might look simpler to build. (You may leave out the resistor) For the U3 check almost any diode will do.

Many experienced constructors first response is "get out the scope" but the time to learn a scope is not when you have a fault..

With a simple probe you should be able to trace the signal and estimate it's level in the short distance it travels in a U3.
And with DC measurements on the PA the U3 must be one of the easiest things to diagnose.

73 Alan G4ZFQ

Thanks for your reply and the links Alex, I will build a probe at the weekend, I have a few 1N4148 diodes, I will let you know how I get on.
73 Colin.

Hi Alan, I had a look at the building instructions again and saw that I had stupidly forgotten to add the jumper for the PA,? I have been running the kit up to now with a separate power supply for the PA, duh, I have spent hours looking for the fault, panic over.
Thanks for your help, 73 Colin.

Hi Hans, I had a look at the building instructions again and saw that I had stupidly forgotten to add the jumper for the PA,? I have been running the kit up to now with a separate power supply for the PA, duh, I have spent hours looking for the fault, panic over.
Thanks for your help, 73 Colin.

forgotten to add the jumper for the PA,

Colin,

Rule 1)
DO NOT PANIC!

73 Alan G4ZFQ

Alan, that should be written on the cover of a comforting book :o)

rule one, remember to take your towel ;-)

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