fox@scicom.AlphaCDC.COM (David L. Fox) (11/25/89)
I am trying to replace the 15 Meg hard disk in my Tandy 12/6000 external
disk unit. A posting of a few weeks ago indicated that this should be
straightforward but I have encounterd a problem, namely three discrete
wires soldered to the drive electronics board and connected to the controller.
The previous posting did not mention anything like them and I am unsure
of what to do about them.
My new drive (a ST-251) will not work without them (I get "drive not ready"
messages when I try to format). Any help or information will be appreciated.
Thanks in advance,
David Fox
fox@scicom.alphacdc.com {boulder|isis|ncar}!scicom!foxdaveb@elaited.i88.isc.com (Dave Burton) (11/28/89)
In article <2262@scicom.AlphaCDC.COM> fox@scicom.AlphaCDC.COM (David L. Fox) writes: |I am trying to replace the 15 Meg hard disk in my Tandy 12/6000 external |disk unit. A posting of a few weeks ago indicated that this should be |straightforward but I have encounterd a problem, namely three discrete |wires soldered to the drive electronics board and connected to the controller. |The previous posting did not mention anything like them and I am unsure |of what to do about them. | |My new drive (a ST-251) will not work without them (I get "drive not ready" |messages when I try to format). Any help or information will be appreciated. NOTE: The following assumes an old style 8x300 based controller. I haven't worked with the newer WD1100 based controller. The three wires may be profitably clipped at the original drive. They provide signals/control lines for the green active light and disk write protect (and the WP light?). I assume you did this already, since you have the 251 connected, presumably installed. HOWEVER, you will need to modify your controller card to enable the non-Tandy HDs. It's been awhile since I did this, so I don't remember exactly what pin I had to change. The essence of the hack was to tie one of the pins on (each) data (20 pin) header on the controller to either ground or +5 (I forget which). The fix was rather obvious from the schematics; refer to the tech ref manual for the 12M external. Sorry I can't be more explicit. I will attest that an ST-225 works great with the 8x300 HD controller once mods along these lines are made. -- Dave Burton uunet!ism780c!laidbak!daveb
uhclem@trsvax.UUCP (11/28/89)
<> B>I am trying to replace the 15 Meg hard disk in my Tandy 12/6000 external B>disk unit. A posting of a few weeks ago indicated that this should be B>straightforward but I have encounterd a problem, namely three discrete B>wires soldered to the drive electronics board and connected to the controller. B>The previous posting did not mention anything like them and I am unsure B>of what to do about them. B> B>My new drive (a ST-251) will not work without them (I get "drive not ready" B>messages when I try to format). Any help or information will be appreciated. The "three wires" are not the cause of your "not ready" condition. Check the drive select straps or terminators IF the format does not even start. If the format starts but gets not ready errors after running a while, you have not covered pin 2 on the "Control" cable. That is the 34 pin cable. Put a piece of electricians tape (not Scotch!) over the pin 2 etch on the drive connector and the not ready errors should go away. You have a drive with a ST412 interface and the II/12/16/3/4/6000 were wired for drives with a ST506 interface. The three wires you speak of implement the ACTIVE light on the front panel, and the ability to write-protect the media. If you can live without either of these things, you do not need the wires. The points those wires latch onto are not present or do not have the desired signals on every make of drive. <This information is provided by an individual and is not nor should be construed as being provided by Radio Shack or Tandy Corp. Radio Shack/Tandy Corp has no obligation to support the information provided in any way. Sorry, nothing funny today....> "Thank you, Uh Clem." Frank Durda IV @ <trsvax!uhclem> ...decvax!microsoft!trsvax!uhclem ...hal6000!trsvax!uhclem
fox@scicom.AlphaCDC.COM (David L. Fox) (01/16/90)
I am still trying to get a Segate ST251-1 (6 heads, 820 cylinders)
to work with my Tandy 12/6000. Thanks again to all who replied to
my earlier message. I believe I have correctly handled all the points
you raised. I have covered pin 2, the drive select jumper is correct,
Tandy's write protect weirdness in the data cable is working, and I
have covered pin 7 of the data cable.
The drive still will not get past the power on boot sequence. According
to the Tandy service manual the boot ROM will seek in 5 tracks and then
issue a restore command to find track 0. I have been looking at the
signals between the drive and controller and here is what I see:
1. Controller asserts DIRECTION IN.
2. Controller generates 5 step pulses.
3. Drive releases TRACK0 and SEEK COMPLETE.
4. After approx. 15 ms drive asserts SEEK COMPLETE.
5. Controller releases DIRECTION IN.
6. Controller generates one step pulse.
7. Drive releases SEEK COMPLETE.
At this point the system hangs, waiting for the drive to complete the
seek. The drive never asserts SEEK COMPLETE.
If I replace the ST251 with a Tandon TM502 (4 heads, 306 cylinders,
similar to the original 6 headed TM503) every things works normally.
I see events 1 to seven exactly as above but they are followed by:
8. Drive asserts SEEK COMPLETE
9. 6, 7, and 8 repeat 5 times until drive asserts TRACK0.
This looks like a bad ST251 except that the drive works fine in an XT clone
and a known good Tandon TM262 also does not work with the Tandy.
The only thing I can see wrong with the above is that the 5 step pulses
in #2 are at approx. 2 ms intervals. This is in the unspecified region
between "buffered seek timing" (<200 us) and "slow step timing" (> 3ms).
Does any one know if this would cause the ST251 to hang in the observed
fashion? Is there any way to change the step rate used by the boot rom.
(A software only patch would be nice but I could burn a new eprom if I
knew the locations to patch. I have Z80 Control System Version 3(120)
23-Mar-87.)
The above reflects my current thinking about the source of the problem
but I may be completely off the track. I have explored more than one
blind alley already. Any and all advice will be welcome.
David Fox fox@scicom.alphacdc.com { isis | boulder | ncar }!scicom!fox
(303)-278-9859 (voice)