Epson SQ-B50/2550 Technical Manual page 233

REV.-A
5.4 DIAGNOSTICS TOOL
This section describes how to use the tool and explains its functions.
5.4.1 Overview
Epson supplies this diagnostic ROM cartridge as a tool for repair and analysis of the 50-2550/850.
With this tool, the 50-2550/850 can be repaired very easily.
Because the tool consists simply of the single ROM cartridge, handling is also very easy.
5.4.2 Description
The diagnostic ROM cartridge tool consists of the following items:
• ROM cartridge (27256 ROM)
• Operation manual
5.4.3 How to setup
Check that the printer power is off, then insert the diagnostic cartridge in the printer's option slot A.
I
ROM cartridge
I
---'Jo
<
Printer>
Option
slot A
5.4.4 Functions and use of diagnostic ROM
This ROM is equipped with 36 diagnostic modes, which can be selected and executed using the LCD
panel and 10 switches.
a) Power-on
If power is turned on with the diagnostic ROM installed, the CPU first lights the READY LEDs on
the control panel.
This indicates that the CPU is operating. If the READY LEDs do not turn on, the CPU is not operating
so check the clock signal (IC 1OC pins 2 and 3), Vx voltage 02 collector), reset signal (IC8B pin 47),
and ROM select signals (IC 11 D pins 3 and 11).
Power LED turns on
READY LED turns on
RAM check start
+
5V supply to the circuit.
Indicates that The CPU is working.
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