Been a bit quiet lately but looks like I'm back in business.
I had 3 problems manifest themselves on about the same time
which made me untold puzzlement and frustration.
1) PSU problem.
U2 worked fine in the beginning but I changed the PSU design and
it kept dying on me. Being what I'd class as noting more than simple
low current DC supply I treated it as such. That meant I didn't
run multiple earths from each voltage regulator and just relied upon
a common series earth on the veroboard layout to connect my
regulators together. Bad move.
The last regulator in the cascased regulator chain, the 5v one
kept dying. In effect it had a 4 inch long earth lead to get to real
earth. The result was everything was fine until 5v regulator was
added and then it honked, and backed up the line.
Adding more earth straps to the whole verobaord layout as if it was
an rf circuit plus decoupling cured it.
Silly me for treating a simple DC circuit as DC circuit rather
than an RF one ;-)
2) Internal ATU problems.
After weeks of succesfull operation I found I could no longer tune
the LF bands correctly. Thinking it was my newly installed quad loop
playing up I concentrated on finding an aerial fault.
Turnout out to be an earth wire come off in the ATU !
3) LPF open circuit.
Once I'd got that lot sorted out I kept getting the output dying
on me. Argggggghh! Now I thought that my new PSU was playing up,
but instead on the 9/12v supply line instead of the previous 5v
line.
By this time I was getting a bit suicidal ;-)
Then I accidentally touched one of the LFP toroids and it flickered back on. Turned out to be a fry joint which after many weeks of use
had decided to show itself.
Now I can start enjoying my U2 again !!!
Aint radio life great eh ?
73 de Andy G0FTD
