1st December 1995Help! I have just bought a disk drive to use with my back up BBC and would like some learned person to write direct to me at the above address, and tell me how to wire it up! The following is all the information I can glean from the said piece of hardware; name on front: EXCELERATOR PLUS.
It is a 5.25" drive and I was told that it was Double Sided - I can't confirm this until it's plugged in. There's an "On/Off" switch at the rear panel and along the side there are three DIN sockets. Two of these have six pinholes, and the other has five pinholes. There is also a small square hole underneath which allows operation of a red two pole dip switch; both are present in the ON position. The person who sold it said it worked with a Commodore power supply unit (The output label states 9v 1a and 5v 1.5a, although the DIN plug on the output side did not fit any of the DIN sockets.). Having taken off the DIN plug and checked the voltages at the wires, they are as follows: Brown (Neg) and yellow (Pos) 5v (on A.C. scale) ...Green (Neg) and white (Pos) 10.5v (on A.C. scale).
The first object is to get power to the disk drive so question one is which write to which pins on which DIN plug/Socket. I assume this would be the five pin socket but internal examination does not give any indication as to which.
The second (assuming the drive works) is would it not be possible to power the drive from the BBC direct, thus saving a PSU? If so, how do I wire this us (Both ends...)?
Third, what wiring do I need to get the BBC to talk to the drive?
If anyone out there can help me, I would be very grateful to receive a written reply with wiring diagrams direct. If there is any one within a 20 mile radius of Nantwich who I could visit with the gear for personal consultation, then a short note with telephone number should be very useful!
In advance, thank you.
Gerry Emson
Hopefully some readers have some experience with Commodore Disk Drives. I don't as such but what I do know about Commodore was that, in common with other manufacturers, they made great efforts to make their stuff as exclusive as possible. For instance, I do have experience of their tape decks. Great play was made of the fact that you could only use a Commodore tape deck as others wouldn't work and might damage the machine. In fact, the only real difference between their tape deck and any other was theirs had a micro switch under the play button which, when activated, sent a 5v signal along a separate line to the computer. This signal was terminated when the play button was released and the computer refused to work unless the 5v signal was present. The solution was to make a separate switch and, using a 5v signal from the computer, relay it back at the same time as the play button was pressed and turn it off at the same time as the play button.
It doesn't really answer your question about disk drives but it does indicate what you are up against.
It would sound as if Commodore have produced some sort of serial disk drive. Most drives work in parallel; that is, there are eight data lines each simultaneously sending their own signals in binary. Serial means that there will only be one data line, the other lines are for the control of the disk which needs to be done and is a little complicated.
Try opening the drive up and see if there is a separate board connected to a conventional disk drive socket on the back of the drive.
I have to say this but you may have to a take a loss on this one. 5.25" drives suitable for 8 bit Acorns are quite difficult to find now. There are a lot of old drives from PCs but these aren't really worth using as they will only work in 40 Track and not Acorn 40 Track either. If you really want a second drive, look for one of the 3.5" drives that are sold for PCs. I recently bought a High Density one for just £29.00 and it works beautifully. In fact, all of the 3.5" EUG #22s were produced on it. Maybe I shouldn't have said that as I haven't had any returns of EUG #22 and don't want to tempt fate.
Gus Donnachaidh, EUG #23
