why I am having blown high and low
output transistors. I plan to put
MUR160 fast diodes across the FET;
my question is: Will one amp be
sufficient when I am chopping at 20
kHz? The MUR160 diodes are rated
35 amps for 8. 3 ms.
AWith a forward current of
(maximum) 3. 5 amps, the
one amp diodes should
work okay. But, if you had a
1 μS delay between turning off one
half bridge and turning on the other,
the fast diodes would not be needed.
Even with the fast diodes, there
should be a 50 ns delay.
QI recently upgraded my old
stereo to a five channel
system. Although the amp
is rated at 100 watts per channel, it
puts out about half that. I’d like to
build a stereo amplifier that would
take the output from the front two
speakers of my five channel system
and drive the 200 watt front speakers.
Preferably one that could be switched
in and out and one in a kit. Thanks.
— Ed Bixby
Re: Vibrator Replacement,
September 2008, page 28.
Although it's possible to replace
the 6X4 rectifier with a solid-state
replacement, I would suggest that
the B+ voltage reading be taken
before and after the modification.
Double-check that you're not
exceeding the voltage rating of the
Early electronic design had
AQKits part number K4005B
looks like what you want. It
is rated 2X100W into four
ohms, but it can be bridged to
provide 200 watts mono into eight
ohms. You will need to buy two to
have 2X200W. The price is $159.95
which seems quite reasonable.
From the size (350 x 62 x 85
mm), I am sure it
is PWM, not
linear. A power
supply kit is also
shows how the
two inputs of the
right and left
bridging and how
I would switch
generous (by today's practice)
headroom in component selection
values, but the leap from a 0.7 volt
forward voltage drop device from
a 20 volt forward drop per section
device may push the original filter
design pretty close to the maximum
rating of the capacitor. Keep up the
— John Mattesini
Response: Thanks for the
feedback, John. I had not thought
of that problem.
the output to take the added amp
out of the circuit.
The driving amp will be
essentially no load when the 200
watt amp is in, and the 200 watt
amp will be no load when it is not
connected to the load. I don’t think
this will damage the amps, but you
should check with the manufacturer
to be sure. NV
■ FIGURE 9
Gizmos that bring your dreams to life!
SurplusGizmos Your Science and Hobby Electronics Superstore
UltraSonic Robot Wheel Robot Arm Kit $54 Multimeter Big display $7.50 1000’s of LED in stock
Sensors from $. 50 10mhz oscilloscope $160 1.8mm, 3mm, 5mm,
$1.75 20mhz oscilloscope $270 and 10mm from $. 40
USB oscilloscope $220 1/2 watt $. 95
1 watt Stars $3.60
UV 5mm $. 95
9V 1 Amp $4
12V 2 Amp $8.50
12V / 5V $15
$1.50 and up
Solar Kits $10
Hobby Motors $2
Retro Civil Defense Radiation
Mention Code NVFGIZ12 and get a
FREE gizmo with purchase.
5797 NW Cornelius Pass Road
Hillsboro Oregon 97124