doesn’t coincide with the raster pattern of a CRT
scan. If, by a slim chance, you can find a video
controller that supports an LCD screen and plugs
into your motherboard’s ISA slot, you’ll still need
to fabricate a cable to connect to your particular
PC Board Sound
180 Q. I read your “Cassette to PC” answer in the September 2004 issue and found myself in
+5V the same boat; however, I don’t need to listen to
the source. I just need to find one line-out
“stereo” plug that fits the earplug jack on my
cassette boom box (good sound, as well as
portable) and the line-in jack on my Sound
Blaster sound card.
Unfortunately, the folks at RadioShack don’t
know anything about anything unrelated to selling cell
phone service. The guys at Fry’s are too busy to have
time for such a trivial sale. So, my quest for the right
connectors continues. Do you have the actual name of the
plug combo I need and a source for them?
Multiple Output Power Supply
a passive LCD screen, then it uses what’s called dual
scanning to paint the image on the screen.
With this method, the screen is divided in half — top
and bottom — and scanned simultaneously to increase
screen brightness. Active LCD displays usually don’t dual
scan, but use a fixed matrix of manipulated pixels that
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A. The sound card uses a 1/8” ( 3. 5 mm) plug and most
boomboxes sport the same connector. This means
the RadioShack 42-373 stereo patch cord should work.
Portable CD/MP3 players uses a 3/32” (2.5 mm)
connector; use a RadioShack 274-373 stereo adapter with
the above cord for this connection. If, by some slim
chance, your boombox has a 1/4” phone plug, you’ll need
a RadioShack 274-367 stereo adapter.
Multiple Power Outlets
Q. Did you, by chance, write about or remember seeing
a power supply circuit that provides 5, 10, and
15 volts? It used an LM317 regulator to get 15 volts. From
that, it used a resistance voltage divider to feed separate
transistor emitter followers for the 5 and 10 volt sources.
Any guidance will be appreciated.
Baton Rouge, LA
Circle #142 on the Reader Service Card.
A. No, but your description makes it very clear as to
how the circuit looked. It also makes me think it’s an
older design — one that can be improved upon using
today’s cheaper, off-the-shelf voltage regulator chips.
My updated design in Figure 7 starts with a 7815 to
provide the central 15 volt source. The 10 volt output is
derived from a 7805 that is biased 5 volts above ground.
Let me explain. The 7805 chip references its output to
ground — its ground. Now, if you float that ground above