[rescue] How to open a TK50Z-GA?

[Richard]

Hi Mouse

This may help

https://lastin.dti.supsi.ch/VET/tapes/DEC-TK50Z/EK-0TK50-TM-002_Jul86.pdf

Like the hardware very comprehensive

Under section 3.4.2 lights
Flashing:
Pushing the load/unload 4 times may clear the fault.

That being said lots more info in there that may help

Richard
Sent from my iPhone

> On 8 Nov 2021, at 03:22, Mouse <mouse at rodents-montreal.org> wrote:
>
> o;?
>>
>>> I've got a DEC TK50Z-GA which appears to be broken.  I offered it
>>> FTGH here on 2021-09-21 and heard nothing in response.  So I infer
>>> nobody's interested - which is hardly surprising.
>> I would be interested if it wasn't so heavy and far away and
>> therefore expensive to ship...
>
> I know the feeling.  I've passed on enough stuff myself (usually in
> Europe, with me in North America)....
>
>>> So I wanted to open it up [...]
>>> But I can't figure out how to open it.  [...]
>> The front bezel is attached to the cover and together they slide
>> forward.  (You do have to remove the screws on the bottom of course.)
>
> Thank you!  That did the trick.  I now have it apart.  (Friction was
> high enough it wasn't obvious they slid until I used a bit more force.)
>
> So, I now have
>
> - A TK50 proper (and according to its markings it is indeed a TK50).
> - A TZK50 SCSI<->TK50 adapter board, 5017638-01-B1-P2.
> - A "LOADS BOARD", "5017162 01 A1", nominally 1.6 ohms of 5V load and
>   12.5 ohms of 12V load.  (See below for details.)
> - An H78948BA power supply, which I have been unable to find specs for
>   but which presumably has a minimum load, or why the load board?
> - Assorted wiring and sheet metal and the like.
>
> The TK50 still appears broken.  Connecting it to power (from a
> different power supply), I still can't get it to release the door lock.
> The button's light is sometimes on solid, sometimes flashing fairly
> fast (10Hz?); pushing it sometimes changes this, sometimes doesn't.
> Unscientific feel says that leaving it untouched for long enough (which
> can be just a second or two or can be more like 15-30 seconds,
> depending on factors I haven't worked out), it goes into its flashing
> state.  Sometimes, toggling it will take it to the solid state,
> sometimes not.  If I knew the TK50 well (I don't) I might be able to
> deduce something from this....
>
> The load board, in case anyone cares, has 15 resistors of 24 ohms in
> parallel on the 5V line, 12 resistors of 150 ohms for 12V, total draw
> nominally 27.145W (though the resistors are only 5% and thus giving
> five places of precision is silly).  Also, 10uF 35V caps, two in
> parallel on the 12V line and three on the 5V line, and five small
> orange devices marked, if I'm reading the tiny writing correctly, RSE,
> 224, ZNI, and 911.  (The R I'm particularly unsure of.)  Three of these
> are in parallel between 5V and ground, two between 12V and ground.
> There are also ten zero-ohm "resistors", which I can't see any point to
> because the points they connect on the etch side are not separated by
> anything and hence could have been connected with etch runs instead -
> and for that matter there are two of them in parallel wherever they
> appear.  (Though "etch side" is a bit of a misnomer, as it's a
> double-sided board and thus both sides are etch.  I should perhaps have
> called it the non-component side.  The component side is almost solid
> conductor, apparently ground plane.)
>
> I'm not sure whether there's anything of value here.  The TK50 proper
> appears broken.  The power supply is less capable than widely (and
> cheaply) available peecee supplies, in that it has a minimum load.  The
> adapter board is of no use without a TK50.  And the load board is of no
> use except with a power supply having a minimum load spec.  The only
> use I see for any of them is as a source of parts, and not much of that
> because there's only one socketed part visible, that being a 27C256 on
> the adapter board.  (The adapter is a Z80 with stock support chips and
> a lot of 74xxx logic.  The one piece that doesn't look stock is a PAL.)
>
> That leaves the case, and, while it's a nice (and seriously rugged)
> case, I doubt I have anything to put in it.  I could scarf up the SCSI
> wiring and ID switch, but that's about it.
>
> It's rather a pity, because, as I would expect from DEC of that period,
> it is impressively well-crafted.
>
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