9 ] Operation Check; Outline/Purpose; Cases Where The Check Is Required; Necessary Tools - Sharp JX-8200 Service Manual

SHARP SERVICE MANUAL JX8200SM [8] ADJUSTMENTS
[9] OPERATION CHECK
List
Section
High voltage OPC drum unit
(High voltage
PWB)
Developing unit
Transfer drum
unit

1. Outline/purpose

This check is performed to check the operations of the high voltage
PWB and the charger unit.
Since this content greatly affects the print quality, this check must be
performed when a trouble on the picture quality occurs.
If a problem occurs any problem, replace the unit.

2. Cases where the check is required

* When a print quality trouble occurs.
* When developer splashes (drops).
* When a paper jam occurs in the transfer drum section.
* When the high voltage PWB is replaced.
* When the transfer drum is replaced.

3. Necessary tools

(Digital multi meter)
* Measurable up to DC 1000V
* True RMS multimeter
* Impedance of 50MΩ or more when measuring the voltage
* High voltage probe (50MΩ)
* Current measurement resolution of 1.0 uA or more

4. Precautions

* Do not replace the high voltage PWB in the field
* Take appropriate precautions with respect to the high output volt-
age.
* Perform the operation check with all the consumable parts (OPC
drum unit, developing unit) installed.
No. Content
1 Main charger current
2 Main charger grid voltage
3 Developing bias voltage
4 Transfer voltage
5 Transfer drum discharger
current

5. Details (procedures)

A. Main charger current check
(1) Outline/purpose
Measure the main charger current to check for an overcurrent or an
insufficient current.
The current value affects the OPC drum surface potential (charging
amount).
(2) Details
1) Disconnect the plug (wire side) from the main charger output ter-
minal on the high voltage PWB.
2) Connect the digital multi meter (current side) between the main
charger output terminal on the high voltage PWB and the plug
(wire side).
3) Enter the normal diag mode and select the VOL TEST MAIN CH
mode with the MENU key.
4) Press the FORM FEED (PAPER EXIT) key to turn on the main
charger. It can be turned off by the RESET key.
5) Check that the current value is within the range below.
–700uA (+50, –20uA)
If the current is not in the above range, perform the following
procedures.
* Check for any current leak or disconnection.
* Replace the high voltage PWB or the OPC drum unit.
(3) Precaution
* Do not keep the main charger ON for a long time. It applies an
electric field to a same position on the OPC drum and the OPC
drum is fatigued locally, causing uneven print.
(4) Troubles generated by abnormal output
* Picture quality defect
* Developer drop (splash)
B. Main charger grid voltage check
(1) Outline/purpose
In the diag mode, let the main charger grid voltage to be outputted,
and check that the proper voltage is outputted.
The voltage outputted in the diag mode serves as the base voltage.
In an actual print operation mode, correction is performed –470 ∼
–732V is outputted.
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