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

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.

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?)

Exactly! It is a RIFA.

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

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.

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.

I was remembering a lingering phenolic reek that took hours to dissipate even with the windows open, but that was from the Schaffner power inlet incident so the scorched potting gunk may well have contributed that particular fragrance :-)

For an evil smell I can recommend a failed selenium rectifier from my youth. IIRC like over-cooked school cabbage. I think I might have its successor in the EHT of my homemade oscilloscope...

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 :-#)#

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

Well.. this RIFA smelled like Texas BBQ. Not too bad actually....

-John

Definitely something to try. I'll give it a shot.

-John

Another TBBS alumni!

I ran The Golddust Plantation back when.

RwP