Disk modification

DA4 HEAD DISK WORKAROUND

The spectacular SL-HF900 and SL-HF750 came from the factory with DA4 video heads. They were responsible for the clear video effects you expected from these full-featured machines. But most of these units today have video heads that are worn out and can't produce a clear picture or plug up all the time. The machine operates fine; just its whole purpose has been taken away, and it ceases to be of any use. The trouble is Sony no longer supplies replacement disks for these two units. They are considered too old to be viable. To overcome this neglect, I have developed a strategy that restores the life and function of these Sony Beta icons. I make them available with a new video head disk* that is compatible. It replaces the old, worn-out DA4 video head disk and gives these VCRs new life. Once repurposed, they produce the same high-quality picture performance as with the original heads; only the BetaScan mode shows a few more scan lines than the original DA4 heads. They did slightly better. All the other features, functions, and goodies are at your disposal in both the

and

playback speeds. This modification is a positive way to resurrect these fabulous Betamax VCRs.
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SET UP AND OPERATIONAL RESULTS

GUIDELINES: The A/V inputs and outputs were used to test the

and

speeds. For the picture evaluation, the industry-standard NTSC composite color bars reference signal from a Leader 408NPS pattern generator was supplied to the video input. For the audio, 1000 and 400 Hertz tones were supplied to the left and right stereo inputs. The Sony SL-0003-C was used for setting back and forward tension, the master alignment cassette KR5-1V was used as the video and audio standard, and a new Sony Ultra High-Grade Pro L-500 was used for producing the test recordings. The RF inputs and outputs were not tested since they are no longer relevant. The VCRs with the new substitution video heads* performed exactly as demanded by the Sony factory service manual. All the video, audio, and machine technical specifications were met. The A' (A sharp) pickup position on the new disk is no longer used and wasn't tested. In general terms, the outcome was as follows.

Picture:
⊠ Recordings made in the SuperBetahi-fi

and

modes played back with
⊠ a sharp picture in both speeds.
⊠ Recordings made in the standard Betahi-fi

and

modes played back
⊠ with a sharp picture in both speeds.
⊠ SuperBeta circuitry acted normally, matching the picture with the recording.
⊠ Pause and step-motion were clear in

and

as the frames advanced
⊠ forward or backward —

and

s had some lines.†
⊠ Scan picture was better in

than

—

and

s had lines.†
⊠ Note: Recordings made in

and

s made using other Betas might not play
⊠ properly in this VCR due to the incompatible disk architecture.

Sound:
⊠ Betahi-fi stereo performance was within specs in all speeds.
⊠ Monaural audio was within specs in all speeds.
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* New original Sony factory part with video circuit modifications.
†.It is normal for the SL-HF900 and SL-HF750 to exhibit some horizontal white lines, streaks, specks, or bars (noise) in their video during the scan, pause, and Step-motion modes. From the factory clear special effects were not available in

and

s, this is noted in the SL-HF900 and SL-HF750 owner's manuals.