Subject: Re: DN10000 X-Bus Terminators
From: "James J. Waldram" <[email-masked]>
Date: Fri, 10 Jul 98 10:16:43 MST
Newsgroups: comp.sys.apollo

There is one 331/471 pack on the terminator which appears not to fail.
The failure modes on the terminators appears to me to be on one set of 
the resistor packs.  These are the seven 101/750G packs that are the 
prevalent packs on the terminator.  These are 10 lead packs (SIP) and 
empirical tests give the following results on a "good" pack.

Dale 10C5-101/750G    (crude drawing)
            ---------------------
            |1 2 3 4 5 6 7 8 9 A|
            ---------------------
             | | | | | | | | | |

Pin to pin resistance:
      1   2   3   4   5   6   7   8   9   A
   1      a   a   a   a   a   a   a   a   c
   2  a       d   d   d   d   d   d   d   b
   3  a   d       d   d   d   d   d   d   b
   4  a   d   d       d   d   d   d   d   b
   5  a   d   d   d       d   d   d   d   b
   6  a   d   d   d   d       d   d   d   b
   7  a   d   d   d   d   d       d   d   b
   8  a   d   d   d   d   d   d       d   b
   9  a   d   d   d   d   d   d   d       b
   A  c   b   b   b   b   b   b   b   b  

      a = 47 ohms
      b = 50 ohms
      c = 22.1 ohms
      d = 85.7 ohms
  eg.  pin 1 to pin 3 measures 47 ohms
       pin 5 to pin 7 measures 85.7 ohms

On failing packs, the resistance varies from the above table, usually
significantly.  My theory is to replace those packs which fail and reuse
the terminator boards.  This theory has not been tested, but I did get
Dale to produce some of the resistors in a custom order.

James J. Waldram                     kb7vdm
Senior System Analyst                [email-masked]
Atmospheric Science Department       [email-masked]
University of Wyoming                ph:(307)-766-5351
Box 3038                             fax:(307)-766-2635
Laramie, WY 82071-3038
USA
--

From: [email-masked] (Wolfgang Zocher)
Subject: Re: DN10000 X-Bus Terminators
Date: 16 Jul 1998 11:27:32 GMT

James J. Waldram <[email-masked]> wrote:
> There is one 331/471 pack on the terminator which appears not to fail.
> The failure modes on the terminators appears to me to be on one set of 
> the resistor packs.  These are the seven 101/750G packs that are the 
> prevalent packs on the terminator.  These are 10 lead packs (SIP) and 
> empirical tests give the following results on a "good" pack.

> Dale 10C5-101/750G    (crude drawing)

Due to an information sheet from Vishey Dale the part 10C5-101/750G is a
dual terminator with 8 series resistor pairs 100 ohm and 75 ohm between
buslines at pin 1 and 10, 75 ohm at pin 1 and 100 ohm at pin 10. The
center tap at the junction of each pair is connected to the remaining
pins...

The remaining real problem is where to get these resistor packs. Dale
offers different packs with different resistor value combinations -
but not the desired 100/75 ohm comb.

Wolfgang Zocher

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 Infos:
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From: "James J. Waldram" <[email-masked]>
Subject: Re: DN10000 X-Bus Terminators
Date: Thu, 16 Jul 98 15:41:02 MST

I had Dale custom build 250 of these packs.  I have enough to share
with others who are interested in trying out the fix...

Previously:
>> Dale 10C5-101/750G    (crude drawing)
>
>The remaining real problem is where to get these resistor packs. Dale
>
>Wolfgang Zocher

James J. Waldram                     kb7vdm
Senior System Analyst                [email-masked]
Atmospheric Science Department       [email-masked]
University of Wyoming                ph:(307)-766-5351
Box 3038                             fax:(307)-766-2635
Laramie, WY 82071-3038
USA