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MAXOPTIX OPTICAL DRIVE with a blown capacitor? Help sought

ironborn65

Well-known member
Hi pals,
I found a Maxoptics TMT3 1300 optical SCSI device; I'm very proud of this finding.
I did some cleaning, tested the PSU that demonstrated to have a good +5V +12V then I decided to turn it on. Suddenly a nasty smell came out of the drive, the smell was the same old stuff that comes out of Mac's PSUs.
I opened it and I found this "thing" that looks like a sort of capacitor to me, weird since it has 4 pins .... Yes, I cleaned it up after taking the pics.
It's close to the input Molex.
Can some expert here help me? How can i replace this thing?
thanks

IMG_20220106_112113.jpg

 

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cheesestraws

Well-known member
on top I can read coil...nics, so maybe it's a coil in acid for isolation purposes ... is it?

Note that the PCB has the 'L1' component designator written by the connections for the device. 'L' almost always means some kind of coil. If it were a capacitor it would be 'C'. Also, it has four connections, which would be wildly unusual for a capacitor, so my guess is that it's some kind of potted transformer for isolation, as you said.

it might be worth seeing if you can make out any more of the text on top of it, or work out what it was connected to...
 

ironborn65

Well-known member
Ah, I notice a blown/shorted DMS capacitor, which was IMO the reason for the exploded inductor, or was the the other way around? It is connected to the solenoid.
The solenoid is made by "Coiltronics" by the parameters are known, I can not read the markings.
One of the trace connects to the +5V of the Molex.
But I'm wondering: if it gets the DC from Molex, why another switching regulator, an inductance and a set of large capacitors? Does it probably need +3V or higher for the optical laser?
 

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cheesestraws

Well-known member
the solenoid is part of the switching regulator section for scaling up

I was just looking at that datasheet and about to post that, too. So it's probably generating a "prosthetic" voltage. Can you poke around with a multimeter in continuity mode to work out where the coil is connected, specifically to what pin of the regulator? (and whether any of those pins are commoned together). Most of the example circuits in the manual seem to call for 50 uH regardless of output voltage, but I wouldn't want to bet on that until we've checked that it's actually wired in where the datasheet says it ought to be
 

cheesestraws

Well-known member
* COILTRONICS 50-2-52 PULSE ENGINEERING 92114

A quick look at that suggests that it's a much physically bigger component, so probably not.

That said, the way that is wired up looks kind of like the "boost converter" topology on literally page 1 of the datasheet: note the inductor between Vin and Vsw, and the diode coming out from Vsw.

Please bear in mind here that I don't really know what I'm talking about, but I'd be inclined to try to find a 50 uH inductor the right physical size for the pinout and try that (although yeah, your diodes and FET may also be fried...)
 

mmu_man

Well-known member
Wow, a company answering someone about an antique device ? A first for me 🙃
Maybe they'd go as far as publishing schematics? 🥺
 

ironborn65

Well-known member
The logo suggests this was a division of Maxtor, who has long since been bought out by Seagate. Looks like this is a reseller of the products now: http://www.mctk.com/maxoptix.html
They have a repair service too: http://yourdrives.com/repairs.htm
The guy at the other side of the email replied that do not make support, he kindly offered to sell a "new" one for $150.
I declined.
I'm still waiting for mtstorage.com reply, in case I'll try to add a 50uH solenoid ...
 

ironborn65

Well-known member
In my thoughts I was wondering if the reason for the leaked/blown of the condenser and the solenoid was .... me :(
I realized that the external fan, connected to the external PSU, was obstructed by the SCSI flat cable when I turned it on.
Switching PSUs needs a load to work properly. As a matter of fact, if I disconnect the fan and test the PSU, I have a floating range from +3V to +5V, with the fan connected I have a stable +5.1V.
Could this have changed the PSU voltage output (lower values) that in turn has stressed the onboard analog boost converter?
It was on for -say- 5 seconds.
oh my ...
 

ironborn65

Well-known member
HI @cheesestraws , I do not believe this is my case
1642067641442.png
because the PCB has 4 pads
1642067676616.png
this might be my case, also because the board already gets a +12V
1642067717086.png
but the spec of the coils is still a speculation.
could it be 2 coils of 50uH each?
thanks for your viewpoint on this
 

cheesestraws

Well-known member
because the PCB has 4 pads

Yes, but look at the pads: they're connected together by tracks in two sets of two. The top and right are connected and the bottom and left are connected. So it can't be wired up as a transformer, or the windings would be shorted out...
 

ironborn65

Well-known member
correct,

then, given the schematic
1642082415809.png
1642082441400.png
and the '1' tag in the PCB
they are in parallel, as boost converter
still it's obscure to me why they need +12V when it's in input from PSU



PF
 

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