Kurzweil PC88 - Page 28

Chapter 2 Diagnostics
Homer Test
The Homer Test confirms that Homer is installed
properly and _ successfully interfacing with the
microprocessor.
Failure of this test indicates a problem with Homer
(U1) or the associated selection circuitry (74HCU04, U8;
19.968Mhz. Crystal, Y1).
While this test is in progress, one should see activity
on Homer's write enable, P126; output enable, P125 and
Data Acknowledge, P119. Also check the address
(BUSA01-BUSA11) and data (BUSD00-BUSD15) pins.
Warning!
Prior to running the Sound ROM and VGM Port Tests,
turn the volume slider to its minimum setting. Loud
tones are present during these tests which could be
potentially destructive to your Sound System!
Sound ROM Test
The Sound ROM Test confirms that Homer can
successfully read the sound ROMs by performing a
checksum of the Sound ROMs. Homer must be
operational before this test can pass, since the processor
must use Homer to read the Sound ROMs.
Failure of this test indicates a problem with Homer
(see above), the Sound ROMs (U25 and U26), or the traces
linking Homer and the Sound ROMs.
While looping this test, one should see periodic
assertions of each Sound ROM’s address, data and select
CS) lines.
PC88 Service Manual
2-10