Crystal DSP Board Operation and Debug
" U32 is AM27C010-90JC
" It is programmed with the latest DSP board CPU code.
" U18 is a Toshiba ?VHC244.
3.4.3 Check On-board Voltages
If any of the on-board voltages are incorrect (except 3.3V; see below)
it is either a bad connector P3 (unlikely) or a board fab problem. A
fab problem in this area indicates a missing connection on an internal
via. There are almost certainly other via problems on the board in
this case. It recommended if this is the case that the board be
scrapped.
" +5V at U6 Pin 1
" +3.3V at U6 Pin 3
" If +5V is present but the 3.3V level is incorrect, replace the
regulator U6.
" +15V at U2 Pin 8
" -15V at U2 Pin 4
3.4.4 Check the main oscillator, clock sources, and Reset Generation
Clock Generation:
" Check the main oscillator output at R1 closest to the Y1 oscillator.
It should be 50 MHz with a 50% duty cycle. If not replace Y1.
" Check R1 is a 33 Ohm resistor.
" Check the 12 MHz clock at R3 closest to U7. It should be 12.288 MHz
with a 50% duty cycle. If not, replace clock divider U7.
" Check R3 is a 33 Ohm resistor.
Reset Generation:
" Check the Reset is not ?stuck? on. The signal level at U8-6 should
be low, and U8-5 should be high.
" If not, check U8-2; it should be high.
" If not, check U20-2; it should be low.
" If not, check R9 (10K) is installed.
" Also, check U20-3; it should be low.
" If not, check R10 (10K) is installed.
" Also check there is NOT a jumper across SW1 terminals.
" Also check there is NOT a switch installed for SW1. It may
be a normally closed switch.
" Check a Reset pulse is generated upon power on.
" Trigger on a positive going pulse at U8-6. You should see a
positive pulse of width 29 msec.
" If not, check C16 is 1 uF. Also check R136 is 100 Ohms.
" Replace U8 if C16 and R136 are correct.
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ACEC
