Small Wonder Labs
PSK-20 Transceiver Kit 03/09/10
2000
25
Troubleshooting the PSK-20:
The "bugs" you're most likely to encounter often turn
out to be caused by the simplest of problems. If your
"PSK-20" doesn't play, here are some general
troubleshooting guidelines.
"It works better plugged in!"
We've all heard that expression before, but
unfortunately it's true. Ensure that DC power is getting
to the PSK-20. A board with no voltage anywhere
probably isn't getting power.
General guidelines:
Check once more for solder bridges and missing solder
joints. Probing a suspect section of the circuitry with a
fingertip or insulated tool will sometimes bring a
stubborn circuit to life- if so, check again for a bad
connection!
Of the returns I see, about 85% of the problems are
caused by cold solder joints, 5% by solder bridges and
5% due to incorrect resistor installation. That leaves
only 5% for all the other problems put together.
Enough said!
•
Ensure that the ICs are installed in the correct
location and with the right orientation.
•
Likewise ensure that the transistors and all diodes
are installed with the correct orientation.
Receiver troubleshooting- general:
Starting at the AF amp (U4-B) input, probe with a
small screwdriver or similar metal tool- there
should be some indication of a signal on the
computer's panoramic display. Repeat this
probing, moving back 'upstream' (toward the
receiver input) through the signal path. If there's a
stage where the chain is broken and there's no
longer any response, chances are good that's where
a problem is!
Transmitter troubleshooting- general:
If an RF signal is getting to the transmitter final
stage, but there's no apparent output, check the
following:
-
measure DC continuity with an ohmmeter across
R54-R56 to ground. This reading should be
approimately 0.5
Ω
.
Doublecheck the installation of T2- a miswire here
assures there'll be virtually no RF output!
If you don't turn up anything with the above steps, see
the troubleshooting information at:
http://smallwonderlabs.com/psk/
An Adobe Acrobat reader (free download) is required
to view these .pdf files. If this isn't convenient for you,
contact me for hardcopy.
•
The figure below illustrates IC pinout. The "pin 1
at lower left" convention applies to all Dual-
Inline-Package (DIP) ICs.
(TOP VIEW)
(BOTTOM VIEW)
8
1
5
4
5
4
8
1
DOT AND/OR NOTCH
"Strange but True"- In general, the ICs themselves
shouldn't be prime suspects during the troubleshooting
process. Despite their complexity, they're very
reliable, and I've had to replace these parts at the rate
of only 1 for every thousand or so shipped!
•
If you're still stumped, contact me for further
technical support:
Dave Benson, NN1G
80 East Robbins Ave.
Newington CT 06111
(860-667-3536)
e-mail: [email protected]
Troubleshooting is available for a flat $40 fee. The
unit will be returned to you in working condition and
will include a troubleshooting report. Contact me for
shipping instructions- this work is currently done
offsite.
