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UNITY TROUBLESHOOTING GUIDE
UNIT DOES NOT “BOOT” (screen is blank)
+ problem with micro-controller PCB #1
- bad PCB connection
- bad EPROM, U703 on PCB #1
- bad RAM, U704 on PCB #1
- bad CPU (80C188), U701 on PCB #1
- bad UART (82050), U708 on PCB #1
- bad “Watchdog” DS-1232, U705 on PCB #1
+ problem with Display PCB
- bad interconnect to motherboard
- bad connection
- bad LCD screen module
+ power 5V is out of 5% supply tolerance
- causing DS-1232 “watchdog” to reset
UNIT LOSES MEMORY
- check UART, U708 on PCB #1
- check RAM, U704 on PCB #1
- check DS-1232, U705 on PCB #1
- verify PS +5V is within 5% of supply voltage
FRONT PANEL BUTTONS DO NOT OPERATE
- loss of any, or all of U9, U11, U12
FRONT PANEL BARGRAGHS DO NOT WORK
- loss of LED +25V supply
+ loss of A/D on PCB #1 (ADC0819)
- sometimes this chip “loses” memory and just needs to be reseated by removing and re-
inserting
+ loss of any or all of the following matrix decoding chips
+ U1, U2, U3, U4, U5, U8, U9, U10, U11, U12
- this may coincide with loss of front panel button operation
FRONT PANEL BARGRAGHS ARE ALL AT FULL SCALE
+ problem with A/D on PCB #1 (ADC0819)
- sometimes this chip “loses” memory and just needs to be reseated by removing and re-
inserting
NO OUTPUT SIGNAL
- discrete output amplifier failure on Motherboard