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Defective Seagate ST-4038 and ST-4051

Xaar

New Member
Joined
Mar 21, 2014
Messages
2
Location
Germany
Hello!

I got two old ST412 MFM drives (Seagate ST-4038 and ST-4051) for testing here. Both drives seem to have the same problem - the top PCB is failing. I also have a fully functional ST-4038 here, so I was able to test some combinations of boards and hard disc bodies. The test environment is a 486SX based mainboard with 16MBytes of RAM (4x 4MB 30p SIMM) with an ATI VGA Wonder XL and the second generation IBM Hard Disc Controller from the 5170. I also used another controller (WA6V WA3V) with no other experiences.

At first I tested both defective drives with their original top PCBs. Both drives spin up and unlock the head sled - but with some heavy noise (sounds like the head sled harshly smashes against the body of the hard drive). Then nothing else happens. My functional ST-4038 spins up and unlocks the head sled - but then it take some seconds until the drive gets quiet (I guess it is reading something from the drive). The both defective drives aren't recognized correctly by the computer (Drive error during POST), the functional drive runs fine.

Because of that, I decided to test the PCBs from the defective ST-4038 on my functional ST-4038. The bottom PCB is fully functional with my drive - the top PCB does not run correctly. With the top PCB of the defective drive my drive behaves like the defective one (also makes a really loud, harsh noise during power up).

I also tested the top PCB of my functional ST-4038 on the ST-4051. With this combination, the ST-4051 runs really nice.

What can I do to repair the both defective boards of this two drives? I recognized that some users here also had defective top PCBs on the ST-4038.

Many thanks!

Best regards, Xaar.

PS: I am sorry for my poor English. I am working on it!
 

modem7

Veteran Member
Joined
May 29, 2006
Messages
8,524
Location
Melbourne, Australia
Welcome to these forums.

What can I do to repair the both defective boards of this two drives? I recognized that some users here also had defective top PCBs on the ST-4038.
The first thing to do is a thorough visual inspection of the PCB, top and bottom. I typically use a magnifying glass. By that method, I once discovered that a faulty PCB on a Tandon TM-100 had a capacitor sheared off.

If the PCBs have socketed chips, then reseat the chips in their sockets.

Connectors should be reseated as well, but you will have done that when you were swapping the PCBs about.

Old aluminium electrolytic capacitors may have deteriorated. An 8" floppy drive that I bought was fixed by replacing the electrolytic capacitors on its PCB.

Beyond that, identification of the faulty component/s usually requires a knowledge of electronics, and a knowledge of how the device works, and a circuit diagram, and test/measurement equipment.

PS: I am sorry for my poor English. I am working on it!
Your English is excellent.
 

Xaar

New Member
Joined
Mar 21, 2014
Messages
2
Location
Germany
Hello!

I have basic knowledge in electronics, but unfortunately it's not enough for finding errors on complex electronic devices. Test and measurement equipment is available: multimeter, logic probe, an oscilloscope and even a logic analyzer (26 years old computer made in the GDR, but it still runs fine).

Well, I will check the capacitors on the PCB - unfortunately there are many of them (esp. ceramic capacitors). Only a few are aluminum electrolytic capacitors (5 on the ST-4038, 4 on the ST-4051). All integrated circuits are soldered. There are also many resistors and resistor networks on the PCB, but to my mind resistors are really reliable. In history I only had defective resistors because they where broken into pieces. Even resistors which got really hot (sometimes it looked as if they already had burned) still had their resistance value.

Are there circuit diagrams available for these hard disk drives?

Best regards, Xaar.
 

modem7

Veteran Member
Joined
May 29, 2006
Messages
8,524
Location
Melbourne, Australia
Well, I will check the capacitors on the PCB - unfortunately there are many of them (esp. ceramic capacitors). Only a few are aluminum electrolytic capacitors (5 on the ST-4038, 4 on the ST-4051).
I only check the aluminum electrolytic ones. Compared to those, the others are reliable.

Are there circuit diagrams available for these hard disk drives?
Not that I am aware of.
 

Willis

New Member
Joined
Jul 19, 2008
Messages
5
Hi there!

I know this thread is more than 2 years old, but it may help some people. There is small coil/inductor (with round black plasitc housing; almost looking like a modern PCs speaker) at the bottom-right corner of the top PCB. By time it's glue dries, and it could be easily teared off by accident. It causes the same error: when calibrating, instead of slowly moving to track 0, the heads are simply shot at full speed with powerful collide... Of course this prevents the drive from seeking properly.
Worth a check. A simple resoldering could cure the problem.

-Willis

P.s.: sorry for my poor english...
 

paul

Veteran Member
Joined
Mar 18, 2004
Messages
809
Location
New Zealand
... ST-4038 ... drives spin up and unlock the head sled - but with some heavy noise (sounds like the head sled harshly smashes against the body of the hard drive). Then nothing else happens.
...There is small coil/inductor (with round black plasitc housing; almost looking like a modern PCs speaker) at the bottom-right corner of the top PCB. By time it's glue dries, and it could be easily teared off by accident. It causes the same error: when calibrating, instead of slowly moving to track 0, the heads are simply shot at full speed with powerful collide...
Just to update this old but still-relevant thread, I've had this same issue on an intermittent basis for a few years now, only on a cold start. Once it's been running it will restart normally even after sitting for a day or two.
Since the inductor appeared fine I replaced the two nearby caps and it seems to be behaving so far. They are 1uF 50V and 220uF 16V.

IMG_0556.jpeg
 
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