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.
I refuse to beleive it takes you over an hour to solder one connection! :-)
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
That does not suprise me. I was under the impression that some very early
Q-bus modules used at least one of those pins for something else (I've
seen 3rd-party Q-bus cards with 22 bit DMA capability where the bus
driver for thsoe upper 4 address lines (normally a '38 or similar) is
socketed with instructions to remove it if used in certain backplanes)
but I suspect the VT103 is late enoguh for this not to be an issue.
The really cool reason to use a VT103 is that a hard drive can be placed
right under the CRT.
I wonder about stray magnetic fields from the yoke and/or flybackj
transformer. Not that they'll corrupt the magnetic patterns on the disk,
but that they'll be picked up by the read amplifier anf cause random data
erros. But I guess it works OK.
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
Do you mean '5 amp' or '5 volt' here? I was under the impression it was
around 15A or so at 5V.
Increasing the rating of a PSU is not easy in general. Many of the
components would need replacign with higher-rated parts, including the
transformer (whether linear or switch-mode), the rectifiers, smoothing
capacitors (increase in capacitance value), chopper transistors (if an
SMSPU), pass transistors (if a linear design), etc.and of course you'd have
modify any current limit circuitry. It'd probably be easier to design a
replacement PSU from scratch to fit in the same space.
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?
About the only thing that'll fail from not being used are electrolytic
capacitors, and I am not convinced this is a major problem with
modern-ish ones. Certainly it's not a failure I've ever encountered (yes,
I've had electrolytics fail, but not by the oxide-film disolving due to
them not being used).
-tony