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Toshiba XM-3401 CDROM leaky caps - Printable Version

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Toshiba XM-3401 CDROM leaky caps - GanjaTron - 08-27-2022

Hi everyone,

a heads-up for anyone still using one of these old dinosaur CDROM drives in/with their SGIs. I have two XM-3401s in my Crimson and PowerSeries, ca. '93 and '95 production, and the earlier one no longer reads discs. I noticed acrid smelling electrolyte on the PCB near the connectors, with a TTL and SMD cap nearby. Popping open the cast (!) lid revealed further leaked electrolyte on the PCB with the onset of corrosion!
 
The major culprits are a bunch of 10µF and 100µF 6.3V SMD caps in an unusual thin can package mounted on its side in a rectangular plastic case (see piccies). Desoldering these things released a stench so intense, I had to open a window and leave the basement. I'm now considering replacing these with 5mm diameter TTL caps, also on their side.

You may of course well argue why even bother with such an old drive if a replacement can still be obtained from eBay. But prices for these drives seem to have gone way up since I bought these in the early 2000s for just 10 DM apiece. Now they're listed for 100€ or more. And I expect the replacement may develop the same issues, unless it's a much newer model. But in my experience these old SGIs don't play nice with every CDROM out there. The XM-3401 is a known working config (once you modify the factory block size, ahem).

FWIW, my other XM-3401 from '95 has the same components, but shows no signs of leakage yet, tho ESR was high (>10 ohms) in some caps. I'm sure this one's timebombs will detonate too, sooner or later.

--Roland

   

   

RE: Toshiba XM-3401 CDROM leaky caps - robespierre - 08-28-2022

Thanks for the alert and pictures of the offenders. A cursory look might misidentify them as tantalum; the "+ –" polarity mark is also strange.

RE: Toshiba XM-3401 CDROM leaky caps - weblacky - 08-28-2022

I've seen caps like these in Insite flopticals and yeah... the form factor was retired YEARS AGO, so the pads are never right for a new cap, best you can do is loop the legs of a cap (think upside-down santa's sleigh) and solder them down. They are simply plastic containers with normal radial caps on their sides. Just dumb.

You did exactly what you could.

Also just because ebay has these drives doesn't magically mean they work, or wouldn't have problems (they are still old and used). I always get upset with people when they say "just go to ebay and get another" when you know it's just as old as what you've got...no better. If you can fix what you have (and knew worked) then by all means, that's the best move. Buy another 25+ year old drive isn't going to help...right? If they were still made, new, that would be a completely different argument.

RE: Toshiba XM-3401 CDROM leaky caps - GanjaTron - 08-28-2022

Thanks for the replies, guys.

Yeah, at first I thought those were tantalums too. And there's another part on the PCB with exactly the same form factor, also containing a "metal can", but turns out to be a crystal. The label gives you a hint.

And as you mention, getting a "new" one of these off eBay for "collector" prices may inherit you somebody else's problems... Rolleyes

I've already replaced the 100µF's from my stock of Pana FR's. Now looking for suitably stubby 10µF's without going entirely miniature, as those have pretty low service life (I just replaced a whole bunch of those in my old Toyota's radio -- another big mess).

RE: Toshiba XM-3401 CDROM leaky caps - soviet - 08-30-2022

Have a couple of old drives like these going to check for caps !.

RE: Toshiba XM-3401 CDROM leaky caps - weblacky - 08-30-2022

(08-28-2022, 01:07 PM)GanjaTron Wrote:  Thanks for the replies, guys.

Yeah, at first I thought those were tantalums too. And there's another part on the PCB with exactly the same form factor, also containing a "metal can", but turns out to be a crystal. The label gives you a hint.

And as you mention, getting a "new" one of these off eBay for "collector" prices may inherit you somebody else's problems... Rolleyes

I've already replaced the 100µF's from my stock of Pana FR's. Now looking for suitably stubby 10µF's without going entirely miniature, as those have pretty low service life (I just replaced a whole bunch of those in my old Toyota's radio -- another big mess).

Not to hijack.  Here's the BEFORE and AFTER of the board from an Insite Floptical (repair didn't solve issue, unfortunately).  Same caps and my method to install NEW caps with a standard radial can, they do fit perfectly in both length and height as the board goes UNDER another metal structure so they had to fit.  This demonstrates my upside down sled technique.

BEFORE
   

AFTER
   

RE: Toshiba XM-3401 CDROM leaky caps - GanjaTron - 09-02-2022

Thanks for the pix, weblacky!

That board's actually denser than on the XM-3401. I couldn't bend the leads back as you did with some of the replacement caps as I had to keep them short so the caps wouldn't protrude into a cutout for the CD spindle motor. As in the floptical, there's not much headroom between the PCB and the mech, but the 4x7mm 10µF's were a pretty good fit. Dropped them in and the drive works again.

   

But... Achtung, Baby! There are two bipolar (!) SMD caps on the PCB. Lacking viable replacements (and space for two back-to-back polarised electrolytics), I left the originals. They still measure ok, but the capacitance is a bit on the low side (<9µF). I expect these aren't stressed as much as the polarised caps. Should replace them at some point, probably with SMD bipolars again.

Now if I could only get my old HDDs to work too... the ST43400 _seriously_ acted up again as I was testing the CDROM, then came to life about 1/2h after tons of failed startups and SCSI bus resets. I have 3 of these bastards, and they all developed the same issue. But that's another story...

RE: Toshiba XM-3401 CDROM leaky caps - aperezbios - 09-02-2022

(09-02-2022, 01:03 AM)GanjaTron Wrote:  Now if I could only get my old HDDs to work too... the ST43400 _seriously_ acted up again as I was testing the CDROM, then came to life about 1/2 after tons of failed startups and SCSI bus resets. I have 3 of these bastards, and they all developed the same issue. But that's another story...

You might want to take a look at ZuluSCSI. It's a relatively new product (launched in May 2022) which supports synchronous SCSI, and incorporates SCSI2SD V6's SCSI command handling routines as a library. ZuluSCSI significantly less expensive than SCSI2SD V6, and can emulate up to seven SCSI devices at once, including CD-ROM. It uses a filename-based configuration mechanism, derived directly from BlueSCSI (The ZuluSCSI firmware is GPLv3-licensed, as is the BlueSCSI and SCSI2SD V5/V6 code base). It's incredibly easy to use, and may make those old ST43400 boat anchors a distant memory, as well as conserve a bunch of electrons in the process as well. 

The GitHub project page is at http://github.com/ZuluSCSI/ZuluSCSI-firmware and there's a ZuluSCSI web page at http://zuluscsi.com

Since you're in Switzerland, I'll send you a PM 

Full disclosure: I own Rabbit Hole Computing, which commissioned development of ZuluSCSI, as a response to critical semiconductor shortages, which have prevented us from being able to manufacture more SCSI2SD V6 and V5.2 boards. I've also had a bunch of SGI gear since long before SCSI emulators were an affordable thing, and had an account on Nekochan for a number of years.

In the interest of not hijacking this thread, please do not ask ZuluSCSI-specific questions here. Instead, I invite you to do so in a ZuluSCSI-specific thread, which I've just now created. Please feel free to participate at Introducing ZuluSCSI (irixnet.org)

RE: Toshiba XM-3401 CDROM leaky caps - Raion - 09-09-2022

Hey no worries about posting about thishere, but next time it's not necessary to go on a 2-3 paragraph post. You can simply say "have you looked at my project here? " And link to the thread!