Active" Terminators; Terminator Power; Test For Internal Termination; Double Termination - Roland VXpanded VS-880 Application Manual

External terminators are usually rectangular boxes which can be attached to a separate 50 Pin Amphenol
connector on the rear of the drive. Other external terminators have a 50 pin connector on both sides so the
terminator can be plugged onto the drive and the cable from the VS-880 can be plugged into the
terminator.
Do not change terminators on any SCSI device with the power turned on.

"ACTIVE" Terminators

"Active" terminators are your best and first choice. These have a voltage regulator inside to make sure the
precise reference voltage is available to minimize cable reflections. Unless external terminators are marked
as "active", they will be "passive" devices. Some new drives have active termination built into the drive
with a rear panel switch that can turn it on or off.
Roland recommends that you purchase drives from a supplier who has exhaustively tested their drives
specifically for hard disk recording or other digital audio and video applications.

Terminator Power

All external terminators (active or passive) require a power source to operate
correctly. This is known as 'terminator power' or 'term power'. Since the VS-880
does not provide this power, your external hard disk drive must provide its own
terminator power. Check with your drive supplier.
If you have a volt meter, you can measure two pins on the 25 pin male end of the SCSI cable attached to the
last device in your SCSI chain. If you measure + 5 VDC between pins 14 and 25, the device is providing the
correct terminator power.

Test For Internal Termination

If you are not sure if your external drive is internally terminated, you can measure this. With the drive
turned on and not connected to any other SCSI device, measure the voltage between one of the data lines
(such as pin 26 on a 50-pin connector, or pin 6 on a 25-pin connector) and the ground (GND) pin listed
above. If the drive is internally terminated, you should measure approximately 3 VDC. If the drive is not
internally terminated, this pin will be "floating" and you may measure something close to 0 or 5 VDC
(your meter may even fluctuate between these two extremes).

Double Termination

Be sure that the last drive in the SCSI chain is not double terminated. That means that it has internal
terminator resistors installed as well as an external 50 Pin terminator. You must remove either the internal
SIPs or the external terminator package. Remember, only the last drive in the chain is terminated.
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VS-880 Application Guide
1 2 3 4 5
14 15 16 17 18 19 20 21 22 23 24 25
GND 25 Pin SCSI Cable End Connector (male)
6 7 8 9 10 11 12 13
+5VDC