Gestetner A193 Service Manual page 102

PCU (PHOTOCONDUCTOR UNIT)
There is no toner end sensor in this machine. Instead, toner end/near-end
condition is detected using the TD sensor output data.
The machine checks for toner near end/end condition every copy. If toner
near-end or toner end is detected during the copy job, it is also checked after
finishing the copy job. To detect toner near end, the machine first decides the
toner end reference voltage (V ) based on the TD sensor initial setting and
TE
the humudity sensor output. Then, the machine compares V with the TD
TE
sensor output voltage (V ): this is point 1 on the flow chart.
T
During a copy job:
If V is greater than V (this means the amount of toner in the
T TREF
development unit is low), the machine supplies toner (see Toner Supply).
If toner concentration is still low after 30 copies (point 2 on the flow chart), the
machine checks for a toner near end condition (if V is greater than V ,
T TE
there is a near end condition).
If toner concentration is still low 50 copies after toner near-end condition was
determined (point 3 on the flow chart), the machine detects a toner end
condition.
After a copy job:
When the machine detects that toner concentration is low, after the copy job
is finished, the machine decreases V by 0.2 V and compares the new V
TE TE
with V ("4" on the flow chart). If the toner concentration is still low, the
T
machine supplies toner. The machine then compares V with V again, and
T
TE
supplies toner again if V is too low.
T
If the toner concentration is still too low after supplying toner 15 times ("5" on
the flow chart), the machine detects a toner near-end condition.
If toner concentration is still low 50 copies after toner near-end was
determined ("3" on the flow chart), the machine detects a toner end condition.
The number of copies between toner near-end and toner end can be
changed with SP 2-213. The default value is 50.
- Toner End Recovery -
If the front cover is opened for more 10 seconds and closed while a toner
near-end/end condition exists and the toner bottle is replaced, the machine
will attempt to recover for 3 minutes using the same procedure as for toner
near-end/end detection after a copy job.
SM 2-41 (A193)