Date: Apr. 30, 1993
COPIER : SF-7800
No. : SP-1576
TROUBLESHOOTING POWER SUPPLY BOARD
DAMAGED BY OVERCURRENT (Q301, SCR301)
1.Model name: SF-7800/7850
2.General: It may possibly happen to damage the transistor (Q301) or the thyristor
(SCR301) of the DC power supply board caused by overcurrent owing to an
abrupt voltage fluctuation. If Q301 was damaged, a voltage above 30V is
added on the 24V line (VB) which may cause to damage IC25 of the main
PWB. To avoid this, these parts (Q301, SCR301) are replaced with new types,
the DC power supply is provided by other vendor, C316 is changed for 100V
series of the domestic version of SF-7870 to prevent a damage caused by a
voltage fluctuation owing to an abrupt service interruption. (for a communal
use of the power supply PWB)
3.Reason: The problem is eliminated f or the DC power s upply PWB t o resist the abrupt
voltage fluctuation.
4.Description: The voltage withstanding property is c hanged for t he Q301 transistor from
100V to 200V, the amperage is changed f or the S CR301 thyristor from 6A to
8A, and the capacity of the C316 capacitor is changed from 3300µF to 4700µF.
However, the change in C316 applies only to t he 100V series machines. The
structure of the heat sink (A303) i s also c hanged to improve the wi re harness
routing job.
Current New Note
Transistor, Q301 0CBUAC0107AZ/ 0CBUAC0247AZ/
Thyristor , SCR301 0CBUDA0063AZ/ 0CBUDA0076ZZ/
Capacitor, C316
(100V series only)
0CBUGAC222GQ/ 0CBUGAC472GQ/
Voltage withstanding
property changed from
100V to 200V.
Amperage limit changed
from 6A to 8A.
Changed from 3300µF to
4700µF.
This change of C316 is for preventing a damage owing to an abrupt service
interruption for the domestic version of SF-7870 only. C316 of SF-7850/7800
are also changed due to a communal use of the power supply PWB. (The
current capacitors of SF-7850/ 7800 have no problems.)
1/4
SHARP CORPORATION Reprography Division
Green
C
Change in the Q301 transis tor
* For the pin layout of the Q301 transistor is changed after the change, the new
transistor cannot be inst alled on the current t ype PWB. Considering t he field
work, the transistor (400V) of the same pin layout is supplied as a service
parts. The circuit pattern of the PWB is also changed to meet the change in the
Q301 pin layout.
4.Action: (Factory action)
Since mid-October 1992 for the 100V series SF-7800 and SF-7850, while Q301
and SCR301 changed since Januar y 1993. S ince September 1992 for the 200V
series SF-7800 and SF-7850. Since December 1992 for the SUKM production.
Current New
100V rated 200V rated
(Field action)
When the problem is met for Q301 or SCR301 on the field, the replacement of
C316 is not required. They must be replaced wi th the new items. P lease note
in this case that i t needs to replac e with the 400V rated Q 301 because it has a
different pin layout from the ex isting Q301. A lso, it needs to use the new heat
sink added besides t he existing heat sink (A 303) as i t needs to enhance the
heat releasing effect as the new Q301 has more heat generation.
Field action Q301 transistor VS2SC3572-/-1 Q’ty=1
Field action heat sink LPLTM4470FCZZ Q’ty=1
Field action screw (M3x8) XBPSD30P08K0D Q’ty=2
Field action SCR301 thyristor 0CBUDA0076ZZ/ Q’ty=1
Notes on replacing Q301
1) Q301 and, D302 and IC302 found besides the Q301, must be in contact
with the A303 heat sink surface.
2) You must add the extra heat si nk (LPLTM4470FCZZ) to t he existi ng heat
sink when replacing Q 301. The exist ing heat sink (A303) mus t be in contact
with the new heat sink in their surfaces and the new heat sink must be
fastened with the existing heat sink using screws (M3x8).
2/4
Q301 and SCR301 replacement procedure
1. Remove the screws from the power supply PWB and remove the baseplate
and the heat sink. (➀ through ➅ in t he figure.)
1
4
5
DC power supply PWB
2
3
6
2. Replace Q301 and SCR 301 with the new items.
Replace Q301 . Replace SCR301
3. Not e the following when replac ing Q301.
1. I t must face in the way shown in the figure.
2. Align the height of Q301 with other items
Heat sink
Newly added
Q301
(IC302, D302).
3. Q301, I C302, and D302 must be in close
contact with the heat s ink surf ace.
4. Add t he new heat sink ( LPLTM4470FCZZ) next t o the existi ng heat sink
(A303).
*1: Both heat sinks must be in contact in their surfaces.
*2: For the sc rews ➁ and ➂ removed in step-1
Screw (3x8)
is shorter as M3x6, these two screws must
be replaced with the new M 3x8 screws
Supporter
(XBPSD30P08K00).
Heat sink (A303)
Extra heat sink (LPLTM4470FCZZ)
5. Reinst all the PWB, using the s crews ➀ and ➃ t hrough ➅.
3/4
Ref.
No.
Model
name
SF-7800
7850
Version P/G No.
100V
series
200V
series
100 V
series
8 -805 CPWBF0909FC31 CPWBF0758FC37 BL
8 -805
805 -A303
All
805 -Q301
805 -
805 -C316
805
805
All
805
Current parts New parts
Parts code Parts code
Price
rank
CPWBF0909FC32 CPWBF0758FC38 BM
0CBLRZ1035ZZ/ 0CBLRH0278ZR/ AM
Parts name
DC power supply
PWB
DC power supply
PWB
Heat sink
0CBUAC0107AZ/ 0CBUA00247AZ/ AV Transistor 4
0CBUDAC0063AZ/ 0CBUDA0076ZZ/ AN
0CBUGAC222GQ/ 0CBUGAC472GQ/ AK
Thyristor
Capacitor
— VS2SC3572-/-1 AM Transisto
— LPLTM4470FCZZ AT Heat sink —
— XBPSD30P08K00 AA Screw (M3x8) —
Effective
time
See
text.
Service
parts
only
<Interchange>
1. Interc hang eable . 4. Not inter chang eabl e.
2. Current type can be used in place of new type.
New type cannot be used in place of current type.
3. Current type cannot be used in place of new type.
New type can be used in place of current type.
Parts marked with “ ” is important for maintaining the safety of the set. Be sure to replace these parts with
!
5. Interc ha ng ea bl e i f rep la c ed w i th s a me t y pe s o f
related parts in use.
6. Others.
specifie d on es fo r m a in ta i ning t he s a fe ty an d pe r fo rm an c e of t he s e t.
Interchangability
3
3
1
3
3
—
Note
See T/R
SP-1454.
Q301
needed
for the
field
action
Heat
sink
needed
for the
field
action
Screws
(x2)
needed
for the
field
action
4/4
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