Finally i solved my problem with MFM hard drive error (Can't write the new VHB : Response = 10)

I got my hands on logic analyzer and good motherboard from unixpc (0.5MB version). I started poking around probes on two motherboards. I realized that the output clock signal from VCO chip 14N pin11 was 5MHz instead of 10MHz and 14N pin 1 was 1 volt
instead of 2 volts.

Long story short - the problem was opamp 17N (LF412). I changed it with LF412CN.

Now i can boot from mfm disk.

On Sunday, August 9, 2015 at 5:11:27 AM UTC+3, DoN. Nichols wrote:

On 2015-08-04, vla...@gmail.com <vla...@gmail.com> wrote:

I have found st-412 HDD. I can use it with WD MFM controller. I can run DOS 3.3 on it.

When i put it to at&t i got the same error -" Error : WINCHESTER:Can't Write the new VHB:Response = 10".
So i have got 2 HDD. I can run DOS from them and have the same errors in at&t.
Maybe the source of errors is at&t?

Yes -- or the cables from the computer to the drive.

There should be two ribbon cables and the power cable.

One ribbon cable is 34 conductors wide

The other is 20 (IIRC).

Both are sensitive as to which end of the connector is on which
end of the corresponding connector on the drive.

Look for either a small triangle (or the number '1') adjacent to
a corner pin -- or for a square pad on one pin at one corner. The
colored stripe on the ribbon cable should go to this end in both cases.

If the system has been modified to accept larger drives or a
second drive, there will be a second narrow cable, and a second
connector on rhe wide cable to connect to the control/status logic of the second drive.

If this is all correct (you could swap the cables between
computers for a test to see that they are good), then the next most
likely things are the controller chip (WD1010 by default, WD2010 if the system has been modified to handle drives with more than eight heads,
or more than 1024 cylinders -- or a second hard drive).

There are also the driver and receiver chips to send and receive
balanced read/write data to/from the disk drive.

If you have the maintenance manual (you can download and print
it now, I believe) you can look up which chips serve the driver and
receiver functions.
Good Luck,
DoN.

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