An SCSI Construction Project
With the advent of increased use of SCSI for peripherals comes the chance that one day you'll need an SCSI terminating resistor. Prepare for a shock, because you might be very surprised at the prices charged, for what you get. Many Manufacturers still have SCSI peripheral hardware priced for the Workstation market, not the PC market. Some prices for SCSI equipment have decreased, but for now be prepared to pay a premium for some SCSI items.
So here you are, with a disk drive mounted internally, and a CDRom hanging off the back of the PC. Everything looks great, but it just doesn't work... Maybe it doesn't even recognize the CDRom. You've checked the connectors, and everything looks good... So what's the problem? Well, did you check the terminators? (Say Whaaat??) Improper termination of an SCSI bus can raise havoc with the Host Adapter's interface circuit, and result in missing peripherals, or intermittent operation and possible loss of data. Well, here's a way to build an inexpensive terminator that will connect to the second SCSI connector on many SCSI peripherals. All you need is a Male 50-pin Centronics type male connector, a small length of solid wire, and 18 resistors of 330 and 18 of 220 Ohms, 1/4 watt. The schematic for connecting the resistors & connector is below (figure TT22), and I'll not go any deeper into construction except to say that if you can't take it from here without explanation, you should buy your terminator instead, as you can do too much damage if you do it wrong.