Read Sharp VC-MH711HM (serv.man15) Technical Bulletin online
VCR990202
Month of Issue: February 1999
Classification: Yellow
Classification: Yellow
VIDEO TECHNICAL BULLETIN
Page 1 of 2
Sharp Electronics (UK) Limited
Reference TBT9902066
Revision 4
White – Carry out as required
Yellow – Carry out as required and whenever the unit comes in for service
Red – Carry out on all units
MODELS
VCM301HM
VCM302HM
VCM311HM
VCM312HM
VCM321HM
VCM331HM
VCM522HM
VCMH711HM
VCMH721HM
VCMH73HM
VCMH731HM
SYMPTOM Failure of the bias oscillator, leading to permanent erase or loss of the linear audio
track during record and playback.
CAUSE
Due to an increase in the localised heat generated by T651, Q651 can go out of
tolerance. This may lead to Q652 and R658 failing as well.
tolerance. This may lead to Q652 and R658 failing as well.
ACTION
Carry out the following circuit change.
1. Replace R658 with the same type.
2. Replace C655 with a 47uF, 16V capacitor.
3. Replace L651 with the one listed below.
4. Replace Q652. If the PWB is damaged so that this component can not be fitted,
2. Replace C655 with a 47uF, 16V capacitor.
3. Replace L651 with the one listed below.
4. Replace Q652. If the PWB is damaged so that this component can not be fitted,
follow the instructions on page 2 to fit a radical component.
5. Replace Q651 where necessary and bending it away from the transformer, as
shown in the diagram below.
REF NO
DESCRIPTION
PART NUMBER
PRICE CODE
R658
Resistor
VRD-RA2EE4R7J
AA
C655
Capacitor
VCEA9M1CW476M+
AA
L651
Coil
VP-DF221K0000
∗
AB
Q652
Transistor
VSDTC323TS/-1
AB
Figure 1: Correct Positioning of Q651
Push Q651 away
from T651 as
shown
from T651 as
shown
Q651 connections (as viewed
from the base of the device)
from the base of the device)
VCR990202
Month of Issue: February 1999
Classification: White
Classification: White
VIDEO TECHNICAL BULLETIN
Page 2 of 2
Sharp Electronics (UK) Limited
Reference TBT9902066
Revision 4
White – Carry out as required
Yellow – Carry out as required and whenever the unit comes in for service
Red – Carry out on all units
Figure 2: Location of Q652
Fit the radial transistor (Q652) as shown in the diagram above.
Note that the pin connections of Q652 are the same as Q651.
C (collector) to the negative end of C655.
E (emitter) to the negative end of C654.
B (base) to the jumper wire J176
E (emitter) to the negative end of C654.
B (base) to the jumper wire J176
.
C
E
B
Display
