?

I repaired L2 as best I could and it measured ok so thought I would give it a try. I suspect on 6AU6 may be part of my problem. I swapped them around and I now have a perfectly functional unit as far as I can tell, except R30 gets scolding hot still. I have 4 more 6AU6 coming.

I measured the voltage at the R40/R31/R30 junction at 132V DC and -5.8V and -5.3V on the other side of R30 and R31 respectively with respect to chassis ground. Why would R30 get twice as hot as R31 given those measurements? Don't they effectively have almost the same current flowing across them ? I desoldered R30 and it measure 3.1kOhm but perhaps something else is wrong with it ?

I think I am getting closer

Regards

Richard

The biggest problem is to be sure the that COG never can get forward
of the wheels.  An 800 pound rack tipping is lethal.  A 2 inch caster
seems to be a bit small for the load, unless it's rated for 300 pounds.
If one of those fails you might have a problem.

I like the metro rack solution, I have a bunch of them.  Adjustable
shelves, 800 pounds/rack easy and it's not too hard to find them
used in the $50-75 range.  Every restaraunt has a few.

  Paul


On Sun, Nov 07, 2021 at 03:27:22PM -0800, Matt Huszagh wrote:

I keep basically all of my large and heavy (mostly HP) equipment on a
heavy-duty shelf I ordered from McMaster-Carr
(). I recently moved and wound up with
less space than I previously had. Before, I left about 2.5' behind the
instrument rack to be able to access the backs of the equipment. But, I
could really use that space in the new spot. So, I thought it might be
nice to put my normally stationary shelf on casters. This way I can roll
the shelf out when I need access to the rear of the instruments and keep
it against the wall for normal use. However, I'd very much like to
ensure my equipment doesn't go toppling over when I move it. I posted
about this on eevblog
()
and received some really great advice, which has gotten me to the
current iteration of the design (more on this momentarily). However, I
wanted to field advice from people on this thread who are probably more
used to large and heavy equipment than most.

I've modeled the shelf + casters in CAD and added pictures to this
post. The leveling+swiveling casters are also from McMaster-Carr
(). Basically, I'll put the shelf on
two C channels. The channel will be bolted to the shelf just below each
vertical column. I've designed the length of the channel to be longer
than the depth of the shelf so that the distance between the center of
the wheels when both wheels are rolled inward is still wider than the
depth of the shelf (24").

Some things to note. I'd estimate the total weight of my equipment
between 500 and 1000 lbs, though I'm guessing. The diameter of the
wheels is only 2". However, I'll be careful to ensure there is nothing
in the path of the wheels when I roll it out or in. Also, this is on
flat, hardwood floor. Most of the weight of the shelf is placed on the
middle two shelves since that's where it's accessible. Obviously from a
stability perspective it would be better if it were on the
bottom. Unfortunately, that's not an option. Though I wouldn't
necessarily be opposed to putting weights on the bottom shelf if people
feel that's a major improvement.

Lastly, a previous thread here
(/g/HP-Agilent-Keysight-equipment/topic/racks_for_older_equipment/72918532?p=Created%2C%2C%2C20%2C1%2C0%2C0&prev=1)
contained some good information about this topic. The takeaway seemed to
be that proper NSF metro racks are a good way to achieve what I'm
looking for. And, from Don's comment, it sounds like this is what HP
used for their mobile cal lab, which is obviously a big
endorsement. However, I've already sunk a good chunk of money into this
shelf and would like to use it rather than buying something new. Also,
my uninformed impression is that my shelf looks a bit sturdier than the
metro racks. I could very well be wrong though and would be greatful to
hear why!

Thanks!
Matt

"Paul Amaranth" <paul@...> writes:

The biggest problem is to be sure the that COG never can get forward
of the wheels. An 800 pound rack tipping is lethal. A 2 inch caster
seems to be a bit small for the load, unless it's rated for 300 pounds.
If one of those fails you might have a problem.

The COG will be roughly halfway into the shelf. And, since I've designed
the wheels to at least be past the edge of the shelf, that should never
be a problem. Each caster is rated for 550lbs. I like these casters
because I can keep the weight off the wheel most of the time and level
the shelf (they're leveling casters).

I like the metro rack solution, I have a bunch of them. Adjustable
shelves, 800 pounds/rack easy and it's not too hard to find them
used in the $50-75 range. Every restaraunt has a few.

Yep, I've got nothing against the metro rack. They look great and when I
need an additional shelf that's probably what I'll go for. But, I'd like
to make this existing shelf work if I can.

Also, I should mention that my CAD rendition of the C channel and
casters are accurate, but the shelf is a rough approximation (in the
interest of time). The McMaster-Carr link shows a good depiction of it
though. In particular, though mounting of the shelf to the vertical
supports is quite robust (not as shown here).

Matt

I keep basically all of my large and heavy (mostly HP) equipment on a
heavy-duty shelf I ordered from McMaster-Carr
(). I recently moved and wound up with
less space than I previously had. Before, I left about 2.5' behind the
instrument rack to be able to access the backs of the equipment. But, I
could really use that space in the new spot. So, I thought it might be
nice to put my normally stationary shelf on casters. This way I can roll
the shelf out when I need access to the rear of the instruments and keep
it against the wall for normal use. However, I'd very much like to
ensure my equipment doesn't go toppling over when I move it. I posted
about this on eevblog
()
and received some really great advice, which has gotten me to the
current iteration of the design (more on this momentarily). However, I
wanted to field advice from people on this thread who are probably more
used to large and heavy equipment than most.

I've modeled the shelf + casters in CAD and added pictures to this
post. The leveling+swiveling casters are also from McMaster-Carr
(). Basically, I'll put the shelf on
two C channels. The channel will be bolted to the shelf just below each
vertical column. I've designed the length of the channel to be longer
than the depth of the shelf so that the distance between the center of
the wheels when both wheels are rolled inward is still wider than the
depth of the shelf (24").

Some things to note. I'd estimate the total weight of my equipment
between 500 and 1000 lbs, though I'm guessing. The diameter of the
wheels is only 2". However, I'll be careful to ensure there is nothing
in the path of the wheels when I roll it out or in. Also, this is on
flat, hardwood floor. Most of the weight of the shelf is placed on the
middle two shelves since that's where it's accessible. Obviously from a
stability perspective it would be better if it were on the
bottom. Unfortunately, that's not an option. Though I wouldn't
necessarily be opposed to putting weights on the bottom shelf if people
feel that's a major improvement.

Lastly, a previous thread here
(/g/HP-Agilent-Keysight-equipment/topic/racks_for_older_equipment/72918532?p=Created%2C%2C%2C20%2C1%2C0%2C0&prev=1)
contained some good information about this topic. The takeaway seemed to
be that proper NSF metro racks are a good way to achieve what I'm
looking for. And, from Don's comment, it sounds like this is what HP
used for their mobile cal lab, which is obviously a big
endorsement. However, I've already sunk a good chunk of money into this
shelf and would like to use it rather than buying something new. Also,
my uninformed impression is that my shelf looks a bit sturdier than the
metro racks. I could very well be wrong though and would be greatful to
hear why!

Thanks!
Matt