JVC SRVS20U
Service Manual

2.18.3 Linearity adjustment The following flowchart shows the linearity check/adjustment procedure.
Connect an oscilloscope (CH: + Slope) and, while triggering it with the HID signal, observe the ENV OUT waveform.

2.18.4 PB switching point adjustment The following flowchart shows the PB switching point adjustment procedure. Load the alignment tape.

Play the alignment tape, then set �ATF� (Auto Tracking Find) in �Deck Controller� of the SSS Software to ON. (Note 3)

The �PB Switching Point� in the Adjustment Utility of the SSS software is adjusted automatically.

Ensure that the ENV OUT waveform is linear and parallel, without a noticeable drop or variation in the overall level. If the waveform linearity is poor or there is a noticeable drop in level, adjust the guide roller by turning it with the roller driver.

2.18.5 Error rate adjustment The following flowchart shows the error rate adjustment procedure.
Record a color bar signal for about 5 minute s. (Note 6)

Set �ATF� (Auto Tracking Find) to OFF using �Deck Controller� of the SSS Software (Note 4). Observe the ENV OUT waveform to confirm that the overall waveform balance and linearity levels vary in accordance with the tracking variation as shown in Fig. 2-18-3. Repeat above steps as required. Is the PB ENV waveform ideally stable and does it vary ideally according to the tracking variation?

While playing the recorded signal, adjust �VCO Center Frequency (ME SP)� or �VCO Center Frequency (ME LP)� in �Deck Section� of the Adjustment Utility. To adjust VCO Center Frequency (ME SP) : Set Viterbi OFF. To adjust VCO Center Frequency (ME LP) : Set Viterbi ON.

No

No
Yes The linearity adjustment is complete if the PB ENV waveform is ideally stable and varies ideally according to the tracking variation. To close, play a prerecorded tape and check the audio and video.

Is the obtained error rate minimum (almost the typical value)?

Yes
The error rate adjustment is complete when the minimum error rate which is no higher than the typical value is obtained. (Note 5)

HID waveform

CH1 CH2

Note 5 : � The �typical value� refers to the following: CH1 or CH2: < 498.; with Viterbi OFF. Inter-channel difference: < 10 times between CH1 and CH2. Note 6 : � It is desirable to use a brand-new tape or an unused section of tape. This is to assure the adjustment reliability because using a damaged tape increases the error rate.

PB ENV waveform

Adjust variation in the parallelism

Fig. 2-18-4 PB ENV Waveform Note 3 : � The VHS section has an A/C head, and the first tracking position can be locked using the CTL pulse and drum FF when AT is off. Therefore, the linearity of the VHS section can usually be adjusted with AT off. However, this adjustment method is not available with the DV section, which does not have the A/C head. If ATF is turned off, the DV section performs tracking only of the speed system. Therefore, as time passes, the servo will be lost and the linearity adjustment will become difficult. Note 4 : � Since the speed servo function is active when ATF is off, there will be no problem even if the DVC ATF function is off, provided that it is for a few minutes.

2.18.6 Error rate measuring method It is not necessary to use the error rate jig (YTU93083) or a frequency counter. The Service Support System Software displays the error rates of video CH1, CH2 and totals. When measuring the error rate of a channel, be sure to total the values of the video and the audio errors.

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