Brother 2060, Service Manual

Page: 98 / 171

VI-15-1
About 55 HIGH VOL MALF
HV MALF occurs under the following conditions.
a. When the resistance of the transfer roller is too low.
b. When the Developing AC bias is not applied.
The reason for low resistance of the Transfer roller is the following cases.
- Paper dust or toner adhered to the roller.
- High humidity circumstance
Low resistance induces poor quality printing, therefore the machine checks it
before every print job.
< How to check the resistance >
The resistance can be checked with a hidden function “TRBIAS V0 TEST”. (Refer to
page VII-4)
- Measurement point
No.9 pin (HVT4) of the P6 connector on the MAIN PCB (not constant output)
- HVT4 signal
Machine status HVT4 (V)
Ready: 0
Main motor ON -- Pre-setting
0
-- paper comes to transfer roller: X
While transferring:
Y
Between a paper and next paperX
Treatment -- Main motor OFF:
0
- X, Y voltage
While pre-setting, the HVPS flow the constant-current 2
µ
A to the Transfer roller
and the Engine CPU monitor the transfer voltage. The Engine CPU fix the voltage
X and Y based on the transfer voltage. It means that the voltage X and Y may
vary based on the resistance of the Transfer roller.
Normally, the voltage X is in the range 1 - 4 V.
- When HV MALF occurs ?
When the voltage X is below 0.27 V, the Engine CPU recognise the resistance of
the Transfer roller is too low and warn the user with displaying “55 HIGH VOL
MALF”.
If the voltage X is known, the resistance of the Transfer roller can roughly be
guessed.
Approx. 1.0 V = 600 Mohm (Bottom limit)
Approx. 3.5 V = 6000 Mohm (Upper limit)
On the part specification, the resistance of the Transfer roller is stated as below.
( For the measurement, the special jig and the equipment are necessary.)
600 Mohm - 6000 Mohm (Flow current measured while 2 kV applied.)
PR99033