"Wild_Bill" wrote...
I suspect that service manuals for this type of industrial equipment may
only be available to authorized service centers.

Hence asking on the group, never know what pirated materials folks have


It's possible that any used VFD may have had a fault before it was
subjected to mechanical shock, so the fault may now be a combination of
faults.


Well, I saw it working (admittedly driving an A/C fan installation with a
4HP motor, not on a lathe) before I bought, and it was all OK then...

Multi-layer boards such as computer motherboards are more difficult to
find cracks on, but double-sided single layer boards are fairly easily
inspected with a bright light source behind the board.. a high brightness
LED may work well, but a high powered LED (not just numerous HB types)
will definitely work.
General close inspection procedures follow, and a good magnifier lamp is
very helpful. A quality handheld magnifier may be sufficient with
exceptionally good lighting (not just glare into your eyes).

Yup, I usually use a 20W halogen desklamp or two behind the board and my
trusty stereo 'scope if investigating SMT boards - my old eyes ain't what
they was!


The heavier objects in the unit are most susceptable to mechanical shock
damage. Production soldering techniques may be fairly good in industrial
equipment, but minor defects may still get passed over in testing/burn-in
phases.

Typical procedures generally involve disassembly and reseating of all
internal connectors, and checking for loose hardware.

Done all that, the ABBs are pretty ruggedly constructed generally
(diecast-alloy chassis, sturdy standoffs and big screws for the boards
etc.) - I suspect there may be cracking or a short in the solder / PCB
tracks behind the connector for the programming panel (a surface-mount RJ12
jack) as that would have taken quite a knock when it was dropped - the rest
of it benefitted from the ABS case "crumple zone"... Luckily I can hide it
inside the machine base out of reach of swarf and inquisitive fingers and
mount the programming panel remotely on the end of a cable - and the case
glued / fibreglassed back together well, despite being a 200-piece jigsaw
puzzle.


Paper and notes can be critical to proper re-assembly. Some folks use
digital cameras to record details.

Pretty easy really - chassis/heatsink with flyleads from the power devices,
two stacked boards with captive connectors, a few mutually-exclusive ribbon
connectors, can't go wrong


If trouble spots aren't found with the previous steps, circuit
troubleshooting often involves checking various circuit paths in the unit
without power applied, typically making schematic drawings and educated
guesses along the way.


What I suspect is that a minor component or three (with tiny, obscure SMD
part numbers on) in the supply to the panel may have popped due to a short
developed by the physical damage - this is where a schematic would be really
handy! Having a bench supply handy, I powered the control panel and all
appears well - the LCD display (newly replaced, original was cracked in
transit...) comes up complaining of lost comm's to the VFD, button-presses
produce TTL-level data on the serial output etc.

Much of the electronic equipment manufactured in recent years fails
without any obvious signs to be spotted on a casual visual inspection..
many of the "smart machines" designed recently just fail to operate when
component faults arise.


Well, at least it was working *before* it was drop-tested! It still powers
up, spins a motor, speeds up and slows down, starts stops and reverses etc.,
gives a nice friendly green status light, so it looks like the power to the
programming/display panel's all that's knackered The panel was an
optional extra, so it works at (presumably) factory default settings without
it - I just want to change a few of those settings!

Looks like tomorrow's free time, such as it is, will be allocated to some
serious squinting and head-scratching...

Dave H.
--
(The engineer formerly known as Homeless)

"Rules are for the obedience of fools, and the guidance of wise men" -
Douglas Bader