Assigning an Alternate Recorder on Grass Valley GVG VPE-251 Edit Controller

This document exists to help you on those rare occasions when you don't want to master your show using the Betacam PVW-2800 recorder as R-VTR. This typically happens only when R-VTR is broken. In such circumstances, I strongly recommend that you use G-VTR as your recorder, because for most purposes U-matic SP is so much better than VHS that it won't show up in your final product, and the U-matic tape machines and tapes are quite robust. Here is how to make the change:

Assigning a non-configured machine to be the recorder

The Grass Valley VPE-251 edit controller can only control up to 7 tape machines at once; 6 players labeled A through F, and one recorder. However, it has enough serial port interfaces to permit 14 tape machines to be cabled up simultaneously. The machine to letter configuration can be rapidly modified by loading alternate configuration files (via the Control/B mechanism) or by modifying the machine assignments by hand.

We presently have 8 tape machines, so one machine must be "left out" of any configuration. The type of video program being edited will dictate which machine can be dispensed with. By default, G-VTR (the Sony BVU-850 3/4" U-matic machine) is left out.

To master a show using G-VTR as the recorder

This is the recommended "fail soft" procedure, when the Betacam recorder has failed.

Preparing G-VTR to be the Recorder -- Disconnect TBC

A very important note regarding using G-VTR as the recorder. Normally G-VTR is configured as a tape player. Both the 3/4" U-matic machines use an external Microtime Tx3-FIT time-base corrector (TBC) when they are used as tape players. In order to use G-VTR as a recorder, you must disconnect the recorder end of the coaxial cable which runs from the "ADV SYNC" output of the TBC into the "EXT SYNC IN" connector on the U-matic tape recorder.

If you don't do this, whenever you are recording the TBC will be fighting against the natural sync of the program video input, constantly trying to advance the sync of the recorder to compensate for the propagation delay of the record electronics. This is a loosing battle. The result will be a master tape which is worthless -- the picture will shift and tear and otherwise look like trash. There is no way to rescue a tape which has been improperly recorded in this manner.

Don't forget to reconnect the "EXT SYNC IN" cable when you move the R-VTR assignment back to another machine.

Swapping a machine with R-VTR

When both tape machines are already configured, the simplest way to select an alternate machine as the recorder is to use the swap feature, which exchanges all the assignments for the two tape machines.

No Dual Port Assignments

The edit controller will malfunction if you attempt to make a recording while having two rows on the device assignment menu with the same PORT number. That is, you can not have port 3 assigned to both R-VTR and C-VTR. For this example, if you configure R-VTR to use port 3, then you must go to the C-VTR line and configure it to use some other port. You can set C-VTR to the previous recorder's port number, or you can set it to port 0, which indicates that the C-VTR is not to be assigned to any machine for the time being.

Because of this, it is much better to use the SWAP feature described above, to exchange all the parameters of the C-VTR and R-VTR assignments, rather than struggling to work out the conflicts.

To master a show using C-VTR as the recorder

Repeating the instructions given above, select the C-VTR, then press SHIFT and "S" (SHIFT and the green A-VTR keytop) to exchange V-VTR and C-VTR.