[GreenKeys] Model 33 Progress

[drlegendre .]

"There’s a pretty ugly looking GE cap also that I haven’t figured out how
to probe while in operation because it’s behind the PCB with all the
resistors."

For reference, this is where ESR meters (Capacitor Wizard, the Blue Meter,
etc.) or other so-called "in-circuit cap testers" can come in very handy.

The vintage testers of this type (PACO, Knight, Eico, etc) do work great,
but watch it as they might use test voltages that are too high for
solid-state circuits.

The modern testers are much better, in that the test voltages are
(normally) too low to turn-on silicon junctions - so things like diodes &
BJTs are more or less invisible to it. And of course, excessive voltage can
swiftly damage / destroy digital logic.

On Mon, Nov 7, 2016 at 9:34 PM, Brad <unclefalter at yahoo.ca> wrote:

> I’ve been reading (or trying to) the technical manual from Sep 1975.  It’s
> quite detailed although very long and in some cases not as specific as I’d
> like.
>
>
>
> I did some poking around before and mostly it all seemed to be correct,
> although the filter cap for the (send/receive?) magnet is gone.  There’s a
> pretty ugly looking GE cap also that I haven’t figured out how to probe
> while in operation because it’s behind the PCB with all the resistors.  But
> I think I will go ahead and get rid of most of these just to eliminate that
> issue.  I really can’t see anything mechanical causing these issues –
> obviously the mechanical side is capable of working.. there’s just
> something preventing it from working consistently.
>
>
>
> *From:* drlegendre . [mailto:drlegendre at gmail.com]
> *Sent:* Monday, November 7, 2016 6:53 PM
> *To:* Brad <unclefalter at yahoo.ca>
> *Cc:* GREENKEYS BULLETIN BOARD <GreenKeys at mailman.qth.net>
> *Subject:* Re: [GreenKeys] Model 33 Progress
>
>
>
> Brad,
>
> Which documents are you working from? There are a number of 33 docs
> floating around, and you might benefit from a larger selection.
>
> And yes, there are a number of caps associated with the TU and KB. Have
> you spec'd out the PSU at all? Measured voltages, compared against spec,
> etc?
>
> Again, I don't have any 33-specific exp. but from listening on this list,
> it's clear that they have a much more complex (and failure-prone) PSU than
> the earlier models. For example. the M15 KSR is pretty much all
> electro-mech - I believe the whole system is AC, and if there are any caps,
> they're on the motor**.
>
> If it were my 33, I'd probably freshen up the PSU (new caps..) as a
> matter-of-course, just to keep that crap out of my hair.
>
> (**This is for basic 117V AC mains units, that don't require one of the
> boat-anchor PSUs down inside the table).
>
>
>
> On Mon, Nov 7, 2016 at 8:28 PM, Brad via GreenKeys <
> greenkeys at mailman.qth.net> wrote:
>
> Sorry for asking this – I do have the manual in PDF but because it’s so
> large it causes my reader to delay 5-10 seconds each time I ‘turn’ a page.
> Definitely want to order printed copies I think!
>
>
>
> Question – is there a capacitor involved in any way with the typing
> unit/keyboard?  It feels to me like we have something where not enough
> power is being consistently delivered.  If I press a letter key and hold
> repeat long enough, eventually the printhead will start moving and typing
> (wrong) characters.  And the punch also starts punching out different
> codes, where before it was only punching the fourth hole in from the right,
> if at all.
>
>
>
> I’ve done my best to clean the contacts and associated pins/wires, but
> that hasn’t made a significant difference, although Line Feed is now
> working if I hit it enough times.
>
>
>
> Going to try to (painfully) flip my way through the PDF here and see if I
> can understand more about how it works.
>
>
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