Service Manual
TANDY 6000/6000-HD
--------------------------------------------------------------------- TAN D Y COMPUTER PRODUCTS ----------------------------------------------------------------------
data and control signals appear at connectors J3 and J2.
By
utilizing separate control output signal drivers for each
drive, the need to terminate only the last logical drive has
been eliminated.
All drive terminators are left in.
However, control signals coming into the controller board
are fed from both drives into a 741S14 (U19) and then to the
WD1010.
Drive select outputs determine which drive is
producing these control input signals.
Read and write data
lines are transferred between drives and controller by means
of an RS-422 standard driver-receiver pair, (U4 and U 5 ).
4.
Data Recovery
a.
System Clock Oscillator
The fundamental clock frequency for the controller board is
provided by a 20 MHz crystal oscillator, U2.
One-half of U3
divides this down to a 10 MHz square wave signal called
2XDR, which is 2 times the drive data transfer rate.
This
clock is again divided down by U18 to provide a 5 MHz clock
called WCLK, which is used to run the WD1010.
b.
Phase Comparator
The phase comparator circuitry is comprised of a PAL16R6A
(U18), a 60 nsec delay line (U37), and 3 D-type flip-flops
(Ul and U7).
When data is being inspected from the drive,
its phase relationship must be determined with respect to
the Vco clock.
The function of the circuitry is to provide
windows during which the leading edge of the incoming data
is compared to the leading edge of the Vco.
The windows are
approximately 50 nsec in width.
The window is initiated by
the leading edge of any data bit as it enters U7-3 (INDATA).
The window is terminated by the same data bit, delayed by 60
nsec, at U7-11 (DLYDATA) or by the Vco output (OSC*) at
Ul-3.
When both DLYDATA and the nearest OSC* edge arrive at
the detector, the detector is reset (by U17-6) until the
next data bit arrives.
DLYDATA sets its detector latch to
produce a pump-up condition at the error amplifier, while
the Vco (OSC*) sets its detector
latch to produce a
pump-down
condition at the error
amplifier.
c.
Error
Amplifier and Vco
The error
amplifier is comprised
of a transistor
pack, U30,
and a low pass filter.
U30 is wired as a balanced current
mirror device that sources or sinks current to the filter
stage.
Whenever the Vco is running slower than the incoming
data stream, the error amp receives pump-up pulses.
The
filter integrates these pulses to provide an average
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Summary of Contents for 6000 HD
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Page 124: ...Service Manual TANDY 6000 6000 HD TANDY COMPUTER PRODUCTS Table 7 5 Input Output Port Map 125...
Page 127: ...Service Manual TANDY 6000 6000 HD TANDY COMPUTER PRODUCTS Table 7 6 Memory Map 128...
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Page 266: ...FIGURE 1 1 DISK DRIVE...
Page 268: ...2 2...
Page 279: ...FIGURE 3 2 CONTROL AND DATA TIMING REQUIREMENTS 3 7...
Page 283: ...FIGURE 3 3 LSI CIRCUIT BOARD ASSEMBLY 3 11...
Page 289: ...FIGURE 3 5 DISKETTE CARE AND HANDLING 3 17...
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Page 294: ...FIGURE 4 4 INTERCONNECT BLOCK DIAGRAM 4 4...
Page 295: ...FIGURE 4 6 TRACK O TIMING 4 5...
Page 304: ...FIGURE 5 2 TIMING DISK FIGURE 5 3 HUB CENTER LINE AND TRACK LOCATION 5 4...
Page 337: ...FIGURE 6 19 HEAD CARRIAGE 6 25...
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Page 373: ...FIGURE 3 5 RADIAL CONFIGURATION 3 7...
Page 374: ...FIGURE 3 6 DAISY CHAIN CONTROL LINES...
Page 382: ...FIGURE 3 11 RECOMMENDED SHIPPING PACK DESIGN CONFIGURATION 1...
Page 383: ...FIGURE 3 11 CONTINUED RECOMMENDED SHIPPING PACK DESIGN CONFIGURATION 1 3 17...
Page 384: ...FIGURE 3 12 RECOMMENDED SHIPPING PACK DESIGN CONFIGURATION 2 3 18...
Page 385: ...FIGURE 3 13 RECOMMENDED SHIPPING PACK DESIGN CONFIGURATION 3 3 19...
Page 386: ...FIGURE 3 13 CONTINUED RECOMMENDED SHIPPING PACK DESIGN CONFIGURATION 3 3 20...
Page 387: ...FIGURE 3 14 LOAD GRAPH 3 21...
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Page 390: ...FIGURE 4 1 TEST POINT LOCATIONS...
Page 394: ...o FIGURE 4 3 READ DATA WAVEFORMS 15 TPR AND 14 TPR o 4 6...
Page 397: ...FIGURE 4 4 INDEX SENSOR 4 9...
Page 400: ...FIGURE 4 6 TRACK 0 ADJUSTMENT 4 12...
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