Suggestions for VT103?
Jerome H. Fine
jhfinedp3k at compsys.to
Sun Dec 28 15:33:47 CST 2008
>Tony Duell wrote:
>>Upgrading the back plane to 22 bits is easy and probably would take Tony
>>Duell only 15 minutes. It will
>About 1 minute per connection on average? That sounds right :-)
Jerome Fine replies:
Glad to know that my appraisal of your ability to solder was accurate.
I figured that dividing
my time by about 100 would be a good estimate.
>>usually take everyone else a few hours. Wire wrap is probably the least
>>difficult to use with a small soldering
>>iron. You will need to use lead based solder. A total of 16 points
>>need to be soldered - 4 for each wire
>>to connect address bits 19, 20, 21 and 22. Leave the insulation on the
>>wire wrap except where the soldering
>>takes place. Probably Al Kossow has a manual with a diagram for the
>>VT103 back plane which show where
>>address bits 19, 20, 21 and 22 are located.
>The only thing to watch for when doing a modification like this is to
>make sure that hte pins you're connecting to have not been used for some
>other singal (and connected by PCB traces). I don't think this is a
>problem with the VT103, but I've never seen one.
As far I my experience is worth, the upgrade to a 22 bit backplane with
the version DEC
provides in the VT103 works VERY well. I watched over at least 6 VT103s
modification and all responded as expected. I also tested each point on
before they were soldered and all points showed an open circuit to
>Glen Slick wrote:
>On Sun, Dec 28, 2008 at 5:15 AM, Jerome H. Fine wrote:
>>>Address bits 18 - 21 are on BC1 - BF1 (SSPARE4 - SSPARE7)
>>>BC1 - BDAL18L
>>>BD1 - BDAL19L
>>>BE1 - BDAL20L
>>>BF1 - BDAL21L
>>A diagram would be helpful to identify the required points on the backplane.
>Page 73 of 76, VT103 BACKPLANE
And as final confirmation, the pdf should confirm that the 4 address
points in each AB portion
of the backplane are not connected to anything else.
The really cool reason to use a VT103 is that a hard drive can be placed
right under the CRT.
For someone who does not look closely, the VT103 will look identical to
a normal VT100.
Thus, when the VT103 is powered up and boots into one of the PDP-11
the look of surprise is quite evident when they are told there are a
pair of small monkeys
inside who are answering the responses typed into the keyboard. :-)
The one problem of using the VT103 is that the power supply is really
too limited, although with
only 4 slots, not a lot of power needed. Tony, perhaps you might be
able to suggest how
the 5 amp supply could be enhanced? On the other hand, with a BA23
being relatively easy
to locate, perhaps it is not worth while even asking. I recently
managed to acquire a 3rd BA123
box (with 12 slots) to be a spare in case one of the other 2 power
supplies on the other BA123
As for modes of failure, how often should a power supply be used to be
sure that keeping it out
of service does not cause a failure when the power supply is used after
a few years? Does anyone
have any recommendations?
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