Faulty Of Playback Picture - Canon ZR70 MC A Service Manual

6-3 Faulty of Playback Picture

<Hints>
In the DV, degradation of picture quality normally appears on the screen as block noise. This is because, if an error occurs exceeding the
ability of the error correction circuit, the block by block information of pictures is not played back properly and thus complemented by
the previous picture information. Normally, such block noise appears on the screen when the error rate has considerably been degraded
due to the degraded tape or the lowered head output, etc. Be sure to check the playback picture quality by the error rate.
<Check Points>
1) Deterioration of Tape Quality
Check if flaws, kinks, etc. are found on a magnetic face of tape or not, and compare it with the error rate of other unit.
2) Error Rate (P. 3-7)
In the service mode, check an error rate of self-recording/LP playback. The specified allowable error rate is 2 × 10
In case of NG, take the following procedure.
(1) Observe a playback envelope. If it is abnormal, carry out tape-path adjustment.
(2) Run a cleaning tape.
Use the cleaning tape of hard type (DY9-1384-000).
[Playback time]
Hard cleaning tape (DY9-1384-000)
* When using hard-type cleaning tape, select the cleaning mode on the product main unit.
(Refer to 4-3 - Cleaning Mode, p. 3-10.)
(3) Check the error rate again.
If the error rate is out of the specified range, clean the tape drive parts (posts, drum) using cleaning paper moistened with
alcohol.
* Take care not to damage the head.
* Do not touch the head with bare hand.
(4) Check the error rate again.
If the error rate is out of the specified range, replace the tape with a new one and check the error rate again. At this step, use a
tape (must be Panasonic LP tape) which has been purchased at a different time. The error rate may become worse due to
inconsistent quality or aging of the tape.
(5) Check the error rate again.
If the error rate is out of the specified range, replace the drum unit.
(6) Check the error rate again.
If the error rate is out of the specified range, replace the mechanical unit.
CHAPTER 3. INFORMATION FOR REPAIR · SERVICE HINTS
: After replacement of the drum unit → 25 seconds
For cleaning
3-19
ZR70 MC A, ZR65 MC A, ZR60 A
-5 .
→ 25 seconds per time, Up to three times