HR-16/HR16B Service Manual 1.00
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7.15 Tape Capacitors
•
Revision A & CA
The blue monolithic block RAM capacitors used throughout the board were found to be
unreliable when used in timing critical applications due to excess leakage current. Here, the
capacitors reside in the tape input path (C11 and C23), and may cause the distortion of incoming
tape signals. Such distortions can cause the loss of tape loading capabilities. These capacitors
should be replaced with either a ceramic disk or film (WIMA) type of capacitor if tape loading failures
occur.
7.16 RF chokes
•
Revision CA & AQ
Occasionally the R.F. chokes on these board revisions (located near the power input jacks)
will bust a lead during shipping. When this occurs, it may not be possible to repair the choke. In this
case it is O.K. to remove the choke and add jumpers across its old location. In most cases this
shouldn't be necessary as the units should have had their chokes hot glued to the board at the
factory. Any units that have loose chokes need to be glued (hot glue recommended) to prevent
future damage.
7.17 AQ reset threshold
•
Revision
AQ
During the development of the AQ main PC board,
one of the prime considerations was to reduce R.F.
emissions to virtually 0. Towards this end, a 100 ohm
resistor (R133) was introduced between the raw supply
voltage and the rest of the circuitry to reduce power supply
noise. This had the effect of increasing the threshold of the
RESET circuit, and was found to cause some units to reset
repeatedly in low power situations (i.e. use of lots of lights
in a club could cause fluctuation in the local power by 15V
to 20V, causing the unit to reset over and over again). R28
is part of the threshold circuit for the RESET line. Originally
valued at 3K, the new value is 1.5K (easily obtained by
adding an additional 3K in parallel). This will bring the
threshold into a more reasonable range.
7.18 AQ R116
•
Revision
AQ
Again an attempt to reduce power supply noise, this
resistor was found to sometimes reduce the power supply
level to the 8031 (and surrounding circuitry) to below the
required 4.75V. It is recommended that a jumper be
soldered across this resistor (located between the 8031
and U6).
7.19 Volume Slider Wiring
Note that the wiring of the volume slider changed
between Revisions CA and AQ. Diagram 16 shows the
correct wiring for each board style.
Diagram 16
