[DSP-10] Beginner problem

[Juan Rivera]

I've just completed the main PCB and am going through the preliminary
voltage checks.  Most look reasonable but a few are wrong.  Since the
instructions say to deal with these voltages before proceeding, I assume
that no software needs to run, and no connections other than power are
required at this point.

The main thing I notice is that the +10T and +10R voltages are both zero.
That makes U1 and U2 pin-3 both wrong since they are also zero.  Pins 1 and
2 of U108 are both zero which must explain the lack of +10T and +10R.

Looking at the circuit I would think that the U110:A power-on reset would
initialize U108 so that all the outputs are zero, and that I need to
software initialize the board - but the instructions say, "STOP!  Don't do
anything until these voltages are correct???"

One odd thing...  The first time I fired up the board I fed it +11.00 at
about 330 mA.  Both LEDS were lit and I burned my finger half off touching
U101.  I removed U101 and fed +10 from U101 pin-3 directly.  Current
remained at about 330 mA or so.  I checked U101, found nothing wrong and
reinstalled it.  Now it runs cooler, the current is still about the same,
and the transmit LED stays off.  I wondered if I might have fried something
that first time I powered it up?  I might have simply left the board powered
up for a long period and now I only turn it on to take a reading and then
turn it back off.  That might explain the burned finger, but not the
transmit LED being lit the first time.

The kit is from TAPR and is rev-c with no part substitutions.  I sure would
appreciate some newbie guidance from you experienced hands!

Juan - WA6HTP


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