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VCR990202 VIDEO TECHNICAL BULLETIN
MODELS VCM301HM VCM321HM VCMH721HM VCM302HM VCM331HM VCMH73HM Month of Issue: February 1999 Classification: Yellow Page 1 of 2
VCM311HM VCM522HM VCMH731HM
VCM312HM VCMH711HM
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.
ACTION
Carry out the following circuit change. 1. 2. 3. 4. Replace R658 with the same type. Replace C655 with a 47uF, 16V capacitor. Replace L651 with the one listed below. 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 R658 C655 L651 Q652
DESCRIPTION Resistor Capacitor Coil Transistor
PART NUMBER VRD-RA2EE4R7J VCEA9M1CW476M+ VP-DF221K0000 VSDTC323TS/-1
PRICE CODE AA AA AB AB
Push Q651 away from T651 as shown
Q651 connections (as viewed from the base of the device)
Figure 1: Correct Positioning of Q651
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
VCR990202 VIDEO TECHNICAL BULLETIN
Month of Issue: February 1999 Classification: White Page 2 of 2
C
E
B
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.
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