Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems.

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Old May 18th 21, 01:07 PM posted to sci.electronics.repair
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Default Westwind Trantor Hard Disk for Osborne Computer

Can anyone point me to documentation or schematics for this?
I have one in pristine condition, until last month when a capacitor blew...

Turns out these use the problematic Astec power supplies identical to
the ones used in the Osborne 01. There is a 0.1uF 250V polymer cap that
tends to blow. In fact, I've had 2 Osborne 01 machines that blew while
in service. I replaced the cap and now they work perfectly.

The Westwind, on the other hand, will not recognize the hard disk.
However the built-in ramdisk does work.

My fear is that when the cap blew, a voltage transient may have taken
out one or more of the large Shugart VLSI chips on the disk controller
board. These chips may be difficult to source these days.

-John

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Old May 18th 21, 08:05 PM posted to sci.electronics.repair
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Default Westwind Trantor Hard Disk for Osborne Computer

In article ews.com,
John Crane wrote:
Turns out these use the problematic Astec power supplies identical to
the ones used in the Osborne 01. There is a 0.1uF 250V polymer cap that
tends to blow.


Is it a RIFA Yellow/clear/foil looking thing, wired across Live/Neutral
as part of the incoming filtration?

If so, these infest other stuff, like ICL One Per Desk PSUs, Apple II+
PSUs, SYMBFile 5.25" external harddrive enclosures etc. and they fail
with a crackle, hiss, bang and smoke. In each case, removing the charred
remains stops the smoke and allows the device to work just fine. Replacing
them with appropriate modern caps is possible too, but not essential
to operation.

https://eevblog.com/forum/chat/old-r...isaster-story/

The Westwind, on the other hand, will not recognize the hard disk.
However the built-in ramdisk does work.


Did the power cut out suddenly when the capacitor went (blown fuse?),
or did you power off in a panic? Could unexpected loss of power have
upset an "old" hard drive (no time to head park?)


--
--------------------------------------+------------------------------------
Mike Brown: mjb[-at-]signal11.org.uk | http://www.signal11.org.uk
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Old May 18th 21, 09:27 PM posted to sci.electronics.repair
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Default Westwind Trantor Hard Disk for Osborne Computer

On 5/18/21 2:05 PM, Mike wrote:
In article ews.com,
John Crane wrote:
Turns out these use the problematic Astec power supplies identical to
the ones used in the Osborne 01. There is a 0.1uF 250V polymer cap that
tends to blow.


Is it a RIFA Yellow/clear/foil looking thing, wired across Live/Neutral
as part of the incoming filtration?


Exactly! It is a RIFA.


If so, these infest other stuff, like ICL One Per Desk PSUs, Apple II+
PSUs, SYMBFile 5.25" external harddrive enclosures etc. and they fail
with a crackle, hiss, bang and smoke. In each case, removing the charred
remains stops the smoke and allows the device to work just fine. Replacing
them with appropriate modern caps is possible too, but not essential
to operation.

https://eevblog.com/forum/chat/old-r...isaster-story/

The Westwind, on the other hand, will not recognize the hard disk.
However the built-in ramdisk does work.


Did the power cut out suddenly when the capacitor went (blown fuse?),
or did you power off in a panic? Could unexpected loss of power have
upset an "old" hard drive (no time to head park?)



That's an excellent point. As soon as I saw the smoke, I hit the power
switch. I may have just lost the data and need to reformat. Of course,
I don't see any utilities to do that. So more exploration is needed.

-John

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Old May 18th 21, 11:34 PM posted to sci.electronics.repair
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Default Westwind Trantor Hard Disk for Osborne Computer

In article ews.com,
says...

On 5/18/21 2:05 PM, Mike wrote:
In article ews.com,
John Crane wrote:
Turns out these use the problematic Astec power supplies identical to
the ones used in the Osborne 01. There is a 0.1uF 250V polymer cap that
tends to blow.


Is it a RIFA Yellow/clear/foil looking thing, wired across Live/Neutral
as part of the incoming filtration?


Exactly! It is a RIFA.


RIFA filter caps are evil little devices. They don't just tend to blow,
they *will* blow, with a thick plume of absolutely foul clinging smoke.
They can turn up in just about any mains-powered equipment from the 80s
or 90s, from kitchen appliances to computers to high-end test gear. Any
vintage equipment that plugs into the wall should be considered suspect
until you've checked its power supply to make absolutely certain of the
absence of the damned things.

They should be replaced with equivalent safety capacitors with the same
X or Y rating, never with a normal capacitor. The equipment will also
generally work without them, though without the associated protection
against generating or receiving EMI.

I once dug *eight* RIFA caps out of the power supply in a Tektronix
VM700T test set, only for the back end of the Schaffner branded power
inlet to explode instead. It turns out that Schaffner filtered power
inlets *also* contain RIFA capacitors, concealed inside a metal casing
and some sort of potting material for an especially unwelcome surprise.

I've also seen a near-identical type of cap under the WIMA brand. These
seem much rarer but are just as treacherous.

I expect Mike's right about the drive, I'm only posting because I've
developed a very specific grudge against these things.

R
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Old May 19th 21, 02:21 PM posted to sci.electronics.repair
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Default Westwind Trantor Hard Disk for Osborne Computer

In article ,
Rayner Lucas wrote:

with a thick plume of absolutely foul clinging smoke.


I must have got the alternate-flavour ones, somewhere between burnt
toast and toffee. Although 100% unwanted when coming out of a piece of
electronic equipment, it's not *that* bad.

If the hard drive is an old shoe-box style one (5.25", full height)
that uses stepper motors to trundle the head out over the disk and
back, then they don't tend to like having the head dropped on the
active disk -- any sign of diagnostic LEDs on the drive, as these
can start giving blink-codes to say "Didn't spin up, there's
a head holding me back!" etc.

--
--------------------------------------+------------------------------------
Mike Brown: mjb[-at-]signal11.org.uk | http://www.signal11.org.uk


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Old May 19th 21, 08:19 PM posted to sci.electronics.repair
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Default Westwind Trantor Hard Disk for Osborne Computer


On 2021/05/19 6:21 a.m., Mike wrote:
In article ,
Rayner Lucas wrote:

with a thick plume of absolutely foul clinging smoke.


I must have got the alternate-flavour ones, somewhere between burnt
toast and toffee. Although 100% unwanted when coming out of a piece of
electronic equipment, it's not *that* bad.

If the hard drive is an old shoe-box style one (5.25", full height)
that uses stepper motors to trundle the head out over the disk and
back, then they don't tend to like having the head dropped on the
active disk -- any sign of diagnostic LEDs on the drive, as these
can start giving blink-codes to say "Didn't spin up, there's
a head holding me back!" etc.


Might need a "Shake & Bake" operation to get it spinning again...I used
to pick up the drive and hold it in my hand, then quickly rotate my
wrist in the direction of spin to free up the heads. Then back up the
disk right away!

John :-#)#
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Old May 19th 21, 09:24 PM posted to sci.electronics.repair
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Default Westwind Trantor Hard Disk for Osborne Computer

On Wed, 19 May 2021 12:19:25 -0700, John Robertson
wrote:

snip

Might need a "Shake & Bake" operation to get it spinning again...I used
to pick up the drive and hold it in my hand, then quickly rotate my
wrist in the direction of spin to free up the heads. Then back up the
disk right away!

I had to do similar with a genuine IBM PC that I'd added a FH (5MB)
ST506 interfaced HDD to that wouldn't always spin up from power-on (I
used it to run the Co BBS (TBBS) and it was typically on 27/7).

I would hit the power switch then sharply twist the whole PC around
about 45 Deg and back (as you say, on the same plane as the platters)
and it always span up. ;-)

Cheers, T i m
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