kaplow@crvax1.DEC (Reach for the Stars) (02/20/86)
Unfortunately for you, this is a common problem when VCRs are used
with older TVs. It has nothing to do with the copyguard on the tapes. I
don't know the technical details of the problem, but the only fix is to
buy a new TV. Someone in my office had the same problem with his 12 year
old RCA, and all works fine with his new SONY.
Bob Kaplow
Digital Equipment Corp.
Arlington Heights, IL
UUCP: {allegra,decvax,ihnp4,ucbvax}!decwrl!dec-rhea!dec-crvax1!kaplow
ARPA: KAPLOW%CRVAX1.DEC@decwrl.DEC.COM
* Reach for the Stars *dsi@unccvax.UUCP (02/21/86)
> > Unfortunately for you, [flag waving] is a common problem when VCRs are used > with older TVs. It has nothing to do with the copyguard on the tapes. I > don't know the technical details of the problem, but the only fix is to > buy a new TV. Someone in my office had the same problem with his 12 year > old RCA, and all works fine with his new SONY. > This problem can actually be fixed. It is caused by gross time base anomalies during the vertical blanking interval, usually from a poorly designed headwheel servo or weirdness in the principal-direction-of-the-headwheel-scan tension. If the VTR is properly set up, flag waving should be minimised. However, even professional monitors like Conrac 5700's have a dual horizontal AFC time constant switch. This changes the time constant of the integrating part of the control voltage which varies the horizontal oscillator frequency. A long time constant is used in consumer receivers which results in accumulated AFC errors but better noise immunity under less-than-suburban RF levels. Shorter time constants result in better "framing" of the picture but noise corrupting the horizontal sync pulse will result in that line being offset. What to do? Try reducing the value of the capacitor which is essentially bypassing the VCO control voltage of the horizontal AFC circuit. Many set manufacturers actually have bulletins on the appropriate changes to be made to the receiver for best performance with VTR, or a notation on the schematic as to what needs changing. David Anthony Director of Engineering DataSpan, Inc