sb634 console

[Alan 'A.J.' Franzman]

---- Original Message ----
> Date:    Thu, 12 Jan 2006 10:26:02 -0400
> From:    "Alex [Temple-Heath List]" <temple.heath at MIWWW.COM>
> Subject: Re: sb634 console
>
> At 07:50 PM 1/10/2006, you wrote:
>> On 1/10/06, jsheinb785 <jsheinb785 at aol.com> wrote:
>>> Does anyone with a console (sb634) have experience with 1/2 of   one of
>>> the LED's which tell the time go dark. I have one in which one side went
>>> dark, but the other half is still lit.
>>>
>>> Is it a transistor, perhaps, which is not working?
>>>
>>> Any suggestions?
>
> If the display modules are the same as used in the GC-1005 clock
> (looks like it) there is currently a source for them at ebay. They
> sell 3 display modules for $25, still open to bids though, and 3 days
> and change to go.
>
> Look for article # 7580528300 or go to:
>
> http://tinyurl.com/auyxa

If only one digit of a 2-digit gas-discharge readout unit (such as these
SP-352s) does not light, it is definitely an anode driver problem and not the
readout itself.  This high-side driver is typically made of an NPN transistor
switching the base of a high-voltage PNP transistor, and it's usually the PNP
that fails. You can tell the PNP is getting weak if digits with only a few
segments (typically "1" and "7") flicker in subdued light, especially if only
one digit of the pair does it.  If both digits have the same symptoms, it
could be both anode drivers drivers or the readout itself getting gassy.  Swap
units around and see if the problem follows the readout or not.

BTW, these "Panaplex" style readouts developed by Burroughs and initially
produced by Sperry (the "SP" in the type number) were later made by Beckman,
then Babcock.  Babcock still sells them today (babcockinc.com) but their sales
are not hobbyist-friendly - minimum order 25 pieces, unit cost north of $60
each.

Best regards,

Alan "A.J." Franzman

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