Here is something that might apply, I found it in my 9121 manual: "Write Protect Error on Initialization - A motor speed check is performed when a disc is inserted to be initialized. If the motor speed is on either side of the tolerance allowed, a Write Protect Error is generated and the disc is not initialized. If your drive is operating properly, this indication is one of a defective disc. Discard the disc."
Another possible reason for getting a "Write Protect" error: are you sure your diskette is not write protected? 3.5" disks are protected when the write protect hole is open, opposite from 5.25" disks (although I believe 8" disks were write protected when their notch was open.) If you found new HP single sided diskettes, they come with a molded-in cover over the write protect hole which you have to snap off to write protect the diskette. After you snap it off you can snap it back into the channel to write enable the diskette later. If your diskettes are used, and the write protect cover is missing, you can put a piece of opaque tape over the hole to write enable the diskette.
At this point my father might have accused me of "trying to teach my grandmother to suck eggs" but you never know - I actually use floppies on my PC so seldom anymore, I have to check to make sure which is write protected and which is write enabled!
Another possibility is that the read/write head is dirty. The 9121 is built with a cooling fan that draws some air in through the disk drive opening where it goes right past the head. This can cause a build up on the head, especially if the drive is operated around cigarette smoke. Radio Shack used to sell head cleaning diskettes for 3.5" drives that came ready for a single sided drive - they had plastic over the top of the media for the head load pad to slide on (you could pull out the perforated plastic piece for a double sided drive). They came with a little bottle of alcohol that you apply to the media (a fibrous, non-woven material) then you put it in the drive and tell the system to try to read the diskette, which would cause the drive to spin the disk and maybe move the head a little. Don't try a cleaner for double sided drives, the head load pad might be damaged! Although you can (I have) put some plastic over the hole (top side) to use a double sided cleaner in a single sided drive.
In another message Fred wrote:
"After your last message I looked again and found faint markings for the four switches from left to right from the back: Test 4 2 1."
My 9121D has S/N 2229A and it is also marked "Test 4 2 1". This just reflects the weight of the bits as they contribute to the HPIB address of the 9121. I have two different manuals. One is just for the 9121D/S and the other covers 9121D/S and 9122D/S. The 9121 manual is dated Jan. 1984 and shows the switches marked "Test 2 1 0". The 9121/9122 manual is dated June 1984 and calls the switches "Left Middle Left Middle Right Right"! HP must have changed the marking along the way and left it to the publications department to solve the problem. The switch settings are the same in both manuals.
The 9121/9122 manual says to always leave the test switch up and only describes the successful result of the normal power on self test: 5 flashes for the 9121, while on the 9122 the LED should stay on for less than a minute then go out - if it stays on for more than a minute, the test failed.
The 9121 manual says there are four different self test modes: power-on, user confidence, remote, and service. Only the first two are described, the other two are documented in the service manual. The power-on self test is the one that runs every time the power is turned on with the "test" switch up and five flashes is the successful result. The user confidence test "is initiated by toggling the selftest switch on the back panel from up to down to up. DO NOT LEAVE THIS SWITCH IN THE DOWN POSITION." I have verified this behavior on my 9121. If I set the test switch to down and then power up the drive, it performs the regular power on self test and stops. If I power up the drive (no HPIB cable) with the test switch up, wait for it to finish the power-on test, and then move the test switch to down, it starts the user confidence test. It doesn't wait for you to move the switch back to up but I do it anyway. This test stops if there aren't write enabled diskettes in both drives (I have a 9121D). If the diskettes are present, it appears to format them one at a time and then it comes back and manipulates them again one at a time. At the end it flashes the LED 10 times.
I've tried different combinations to get the different error messages Fred has reported. If I try to read a blank diskette with either plain "CAT" or "CAT" with a correct MSUS, I get "error 130 - disc". If I try "CAT" with an incorrect MSUS I get "error 131 - time-out". This is on an HP87XM with a 9121D.
In his latest message, Fred says:
"The closest I can come to initializing is to get an Error 60 ; Write Protect. This is with all four back switches in the up position."
This corresponds to address 7. If I specify ":D700" in an Initialize command with my 9121 set to address 7, I get a timeout error. I have to specify ":D770". On the other hand, if I don't specify the "MSUS" (the ":D700") at all, the system initializes my left hand drive (only peripheral on the HPIB). If I can assume Fred is not specifying the MSUS, then it shouldn't matter what address his drive is set to (if it is the only HPIB device attached) so the results he is getting indicate an intermittent condition. If the same diskette was used each time "Initialize" was issued (alone - no MSUS) with the drive set to different addresses, and it only gave the write protect error at address 7, it could be a coincidence and the write protect error might be due to the motor speed being out of tolerance at the time the address was set to 7. If the other attempts resulted in a "error 130 - disc" without the write protect error, it could mean that the motor speed was OK, the drive attempted to write the format on a track, and then the following read to verify the format failed. This could be because the drive didn't actually write anything but it could also be because the head is too dirty to read anything, or it could be that the motor speed was OK at the moment it was measured prior to the write operation but in fact the motor speed is not under good control and is now too far off to successfully read the data that was written. The individual diskette can be the cause of the motor speed problem because the friction between the media and the liner is the main load on the spindle motor.
I would definitely try cleaning the head. I've had cases where just cleaning the head made a system go from not working to working. Also, I think the drive should be able to work somewhat with ordinary (high density - that being the most common avaiable these days) diskettes. I just tried one to be sure - didn't even cover the "Density" hole, although I have heard that some low density drives just happen to have a microswitch in that location to sense when a diskette is inserted. You should be able to get it working with High Density media - think of it as a margin test - and save your hard-to-find double density media for reliable use.
BTW, there's no reason you can't use double sided/double density diskettes with the 9121. My 9121/9122 manual has an addendum page to make that clear. The only disqualification is "Double-sided HP media in double-sided format" which won't work in the 9121 for obvious reasons. "Double-sided HP media in single-sided format" is OK as is "HP software -- single-sided or double-sided media", this must mean that HP distributed all their software on a single sided format - no wonder they fill up so many diskettes!
The only media disqualification I am aware of - disregarding the IBM PC/AT "360K media in a 1.2M drive" dilemma - is that you should never use single sided media on a double sided drive because the "other" side of single sided media has not been burnished and so is too abrasive for the head. On this addendum, regarding single sided HP media (which may be burnished on both sides, for all I know) in a 9122 (double sided drives), HP says "exchange only", which HP doesn't spell out but I imagine they mean it is OK to do it to load a file into the computer but not for regular read/write use.
Vassilis: Fred wrote in one of his messages:
"At present all four switches in the back are in the down position and none are marked "Test". When the HP9121 is first turned on the red LED flashes 4 times."
Since his 9121 may be in test mode, do you know what 4 flashes means?
One encouraging note for Fred: my 9121/9122 manual says if you are using a 9121 with Series 200 Basic 3.0, "the device type is HP8290X or HP9121." Also my 9121 manual says "The 9121D/S drive emulates the 82901 drive." This indicates that the 9121 was designed to be functionally equivalent to the 8290X which were the 5.25" HPIB drives, so moving files from those diskettes to the 9121 should be no problem (once the hardware cooperates!)
