DYNACO PAT-5 Посібник з монтажу - Сторінка 17
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Final Re-Assembly
Once you have verified correct voltages, it's time to return your PAT-5 Preamp to
service.
Unplug the power cord and let the caps discharge for a minute before going
In normal operation, the hottest heatsink temperature, U2, will be around 77
2
C (170 F)
. Dress the transformer and power wires away from the heatsinks.
Use a plastic cable tie if you feel it's necessary to keep a wire spaced away
from the heatsink(s).
If your PAT-5 is wired for 240 Volts, make sure that the wires in eyelets 9,
10, and 11 will not touch the top of the chassis or the power supply
mounting brackets.
Place the cover on the preamp. Note that there is only one correct
orientation. You'll see the 4 holes on the sides line up when the orientation
is correct.
Install the 4 black screws (2 on each side) that hold the cover in place
Install the black screw that holds the center-back of the cover to the back
panel.
About the Design
The new power supply design uses bigger capacitors and electronic regulation to
dramatically decrease the amount of hum and power-line harmonics that appear in the
power supply output voltages. Decreasing the hum in the power supply outputs can also
decrease the hum present in the signal paths
The electronic regulation in the new power supply is much superior to that in the old
power supply. The output voltage changes by much less than 10 mV as the output load
moves between no load and full load. The stock design showed more than 1 volt of
change from no-load to full load.
The load regulation method is still linear regulation, so there will be power dissipated in
the heat sinks. They will get quite warm in normal operation. The design was tested with
150 Ohm loads on each of the 15-volt outputs (e.g. 100 mA), and a 4 kOhm load on the
42 volt output. Under those conditions, we measured the following temperatures on the
tabs of the power devices (ambient temperature was 22 degrees C, input line voltage was
120 VRMS, 60 Hz):
U1 – 43 degrees C
U2 – 74 degrees C
2
The resistor bodies from the original supply ran even hotter!
3
Of course, there still may be some small amount of hum when you connect your PAT-5 to other
components as a result of ground loops between the components.
Dressing the wires
on.
Putting on the Cover
3
.
Page 17 of 18
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