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Seagate ST-412 issue.

It's Xebec controller, it only support 10 Megs drives.

I thought that is power issue. St-412 need at startup 3.5 amps.
In my XT there are 2 power cables P10 and P11.
I tried disconnecting FDD, but HDD still don't work at startup.

Hmm... very interesting...
POST don't see the drive if it have P10 cable attached, normally it have P11 and everything is okay.
Drive still work, because I connected it back to P11 and it was seen.

It could be power issue... I'am waiting for your ideas.
 
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In case you are not aware, later XT's (those with 20MB HDD) had a Xebec controller with a DIP switch block. That controller supported four different drive types.

In every IBM and clone PSU I've ever worked on, the wires from the power connectors are soldered to the same point in the PSU. For example, the +12V wire from each connector is solder to the same +12V point within the PSU.
Therefore if P11 fires up the HDD, then providing that P10 has the same four wires (+12V, GRND, GRND, +5V) then it should also power up the HDD.

If not, there may be a broken wire (rare) or one of the cylindrical metal contacts in the P10 connector has opened up too wide. First, check for a broken wire by measuring the voltages on the P10 connector. You should confirm the continuity of the GRND wires also, and so I suggest the following sequence:

1. Do not plug P10 into anything (IMPORTANT).
2. Connect NEG of multimeter to the PSU case.
3. Connect POS of multimeter to the +12V contact in P10. Multimeter should show +12V. This checks the +12V wire.
4. Connect POS of multimeter to the +5V contact in P10. Multimeter should show +5V. This checks the +5V wire.
5. Whilst leaving the POS of multimeter on the +5V contact in P10, move the NEG of multimeter to the first GRND contact in P10. Multimeter should show +5V. This checks out the first GRND wire.
6. Move the NEG of multimeter to the second GRND contact in P10. Multimeter should show +5V. This checks out the second GRND wire.


If that all measures okay, then I think one (or more) of the cylindrical metal contacts in the P10 plug has opened up too wide. This was a known problem in the days of the XT/AT. Some equipment (eg. FDD, HDD) had pins in their power supply sockets that were either smaller than normal, or larger than normal. If you moved a power plug from a device that used large pins to a device that had smaller pins, instant power related problems appeared.
Widened contacts in the plugs were also caused by repeated insertion/removal of the plugs (particulary if a wiggling motion was used).
 
Stettings are correct? I think that this is something like DIPs:

dipnie8zj.jpg
 
modem7 said:
In case you are not aware, later XT's (those with 20MB HDD) had a Xebec controller with a DIP switch block. That controller supported four different drive types.

Oh, that's handy to know as I have the same Xebec controller! Do you have the details of the different drives this card supports? :)
 

Dongfeng,
Code:
         │  1  │  2  │  3  │  4  │
─────────┼─────┼─────┼─────┼─────┤          
type 1   │ ON  │ ON  │ ON  │ ON  │
type 16  │ ON  │ OFF │ ON  │ OFF │
type 2   │ OFF │ ON  │ OFF │ ON  │
type 13  │ OFF │ OFF │ OFF │ OFF │
where:

type 1 = 306 cyl, 4 heads, 128 WPC, 305 LZ, 17 S/T (10.2 Mb)
type 16 = 612 cyl, 4 heads, 0 WPC, 663 LZ, 17 S/T (20.3 Mb)
type 2 = 615 cyl, 4 heads, 300 WPC, 615 LZ, 17 S/T (20.4 Mb)
type 13 = 306 cyl, 8 heads, 128 WPC, 319 LZ, 17 S/T (20.3 Mb)


The type 1 catered primarily for the Seagate ST-412
The type 13 catered primarily for the IBM WD25 (a full height 20MB drive supplied with XT's)
The type 2 catered primarily for the Seagate ST-225 (a half height 20MB drive supplied with XT's)


If you had a HDD that that card didn't support, you would normally go and buy a third-party controller board that could.
In other cases, some IT support areas removed the boards PROM and replaced it with one that they had reprogrammed (altered the area that contained the drive information).



 
Luke said:
Stettings are correct? I think that this is something like DIPs:

That 'thing' is what IBM called a shunt module. In a HDD (and diskette drive) it is used mostly to configure the 'drive select' logic. It is in the correct position/alignment.

More importantly, your picture shows me something I had forgotten about - something that can cause intermittent HDD errors. The chip labeled "T-RES" is in fact a terminating resistor pack. There must be one on the HDD that is attached to the final connector of the controller/HDD cable, and any other HDDs attached to the cable must have the resistor pack removed. If that rule is not obeyed, poor communications will result between the controller and HDD (due to signal reflections on the cable).
You have only have one HDD and so I expect to see a terminating resistor pack in place. Yours is there and is oriented correctly.

Note that diskette drives of the period use the same system - the diskette drive attached to the final connector must have a terminating resistor pack, and any others on the cable must have their terminating resistor pack removed.

Note that different drives mostly use different terminating resistor packs. That is, a Miniscribe 4567 might use a part number 1234 terminating resistor pack, and a Rodime 6543 might use a part number 5678 terminating resistor pack. They are not interchangeable. Therefore, if you need to remove a terminating resistor pack from a HDD (or diskette drive), tape it somewhere on the drive.
 
Just like dirt/corrosion can build up on the pins of RAM chips over a long period, the resistor pack is similar.
It is worth removing/reinserting the pack a few times to remove any such build-up.
 
Looks like it helped. I'am not sure,
I will power XT again after 2 hours and see if it really helped.
 
Remember, your drive might be good. It could be the controller that's intermittent, or a bad cable, etc.
That's why you should find another MFM HDD soon (or move the ST-412 to another computer), so you can quickly prove/disprove your ST-412's serviceability.
 
That didn't helped for long.
But I might find out why it's not Okay.

Look:

screwfn6.jpg


Is screw here requied?
Maybe it's not screw, my English dictionary is missing somewhere, but you know what I mean?
I saw Jorg's pic of ST-412's motor:

412.jpg
 
My ST-412 looks slightly different than both of those. It has a small
allen screw that extends slightly through where that white
part is on yours. I think this sets the Track 0 position. My idea
is to turn the screw in, which should push the arm down
and move the track 0 to another position on the disk.
Then run a low level format. The original post about this solution
specified 'primary formatting software', I think they mean low level
formatting.

My problem is the allen screw is SO small, I haven't found an
allen wrench to fit. But I will, eventually.

If your problem is intermittent, its probably not related to a bad track 0.
 
But... maybe disk have problems with positioning?
When I do 'cold' power up maybe motor can't reach track 0 and so after warming up, motor is able to move to track 0 and propably set the head, so it can read whole disk...
 
But... maybe disk have problems with positioning?
When I do 'cold' power up maybe motor can't reach track 0 and so after warming up, motor is able to move to track 0 and propably set the head, so it can read whole disk...

Thats possible. I think the arm should rotate all the way clockwise, so that
it touches that white stop. That indicates the track 0. Try running the
computer and see if this is true when it warms up.

Unfortunately my problem was caused by the original owner not parking
the head before shipping to me. Its a lesson learned :) Next time I will mail
a diagnostic diskette and have them park before shipping :)
 
Now computer is in parts, I'am planning to clean it...
I must do it tomorrow and check if it really reach that white screw.
 
Now computer is in parts, I'am planning to clean it...
I must do it tomorrow and check if it really reach that white screw.

If you have the XT Advanced diagnostics diskette, there are some tests
you can run, and watch the arm move from one end to the other.
I think its called "Measurement test"
 
If you have the XT Advanced diagnostics diskette, there are some tests
you can run, and watch the arm move from one end to the other.
I think its called "Measurement test"

Heres a closeup, you can see the screw that provides
a stop for the arm.
 

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