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recapen(at)earthlink.net
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 Posted: Sun Jul 16, 2006 6:19 am Post subject: VM1000 light system failure |
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Fellow listers,
Anyone out there experience a failure mode with their VM1000 internal
lighting system? The lights worked up until a few days ago...I'm trying to
remember if I have done anything to the lighting system that might cause the
failure mode sooooo........
Here's the troubleshooting that I have already done:
Pin 20 has 13.3 VDC
Pin 21 has between 4.1 VDC and 10.8 VDC depending on the dimmer setting
Pin 22 has continuity to ground
These three are 'as designed' in my opinion - so the proper stuff is at
least getting to the DPU.
Is there something that I can check on the cable between the DPU and the
display?
I've sent a note to Vision Microsystems - I'll post their response.........
Ralph Capen
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bakerocb
Joined: 15 Jan 2006
Posts: 727
Location: FAIRFAX VA
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| Posted: Mon Jul 17, 2006 7:46 am Post subject: VM1000 light system failure |
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Responding to an Avionics-List message previously posted by: "Ralph E.
Capen" <recapen(at)earthlink.net>
7/17/2006
Hello Ralph, I went through a struggle with my VM 1000 instrument lighting.
I have VM instruments in addition to the main display. I won't bore you with
all the details but here are some of the essential elements.
1) The instrument lights require alternating current that is generated by a
small inverter inside the DPU. VM says to determine if this inverter is
running or not by listening for the hum. This never worked for me.
2) You can do a check on the electrical output of the inverter to the
lights. Disconnect the ribbon cable connector farthest from the DPU and
probe the last two sockets on the ribbon cable (opposite the Red striped
pin). You should have at least 89V AC (rms) across them with the unit
operating and the lights turned on.
3) Do this check very carefully. Use a couple pieces of the the smallest
size safety wire (0.020 diameter) to probe the sockets on the ribbon cable
so that you don't destroy the sockets. Probe only those two sockets which
are ground and the AC supply. If you happen to send the AC supply back to
the DPU on one of the other sockets you can damage the DPU. Don't ask how I
know this.
4) If it turns out that you are not getting the desired AC voltage across
these two sockets then you probably have one of three problems. Either the
inverter is not working, or the AC supply wire is broken, or the AC supply
wire is grounded out somewhere along the ribbon cable.
5) Before you pack up your DPU and send it off to VM for inverter repair you
can check out the ribbon cable. Remove the cable completely from the
aircraft and probe the sockets in the end connectors for the ground wire,
the AC supply wire, and the wire next to the AC supply wire separately to
ensure continuity and no cross connection. If all three wires check out OK
you probably have a failed inverter.
6) If the ribbon cable checks out bad you can get a replacement cable from
VM or you can buy the parts and make up a cable yourself. (Contact me for
parts identification.) In either case you will be required to fasten the
connectors onto the ribbon cable. Be careful about how you orient those
connectors so that they align properly with your DPU and instruments.
7) After ribbon cable assembly I would check out every single socket on
every connector for continuity and no cross talk before installing in
airplane.
 VM, and particularly David McCluskey, are great people to do business
with. Please keep us informed on your progress.
OC
| Quote: |
Fellow listers,
Anyone out there experience a failure mode with their VM1000 internal
lighting system? The lights worked up until a few days ago...I'm trying
to
remember if I have done anything to the lighting system that might cause
the
failure mode sooooo........
Here's the troubleshooting that I have already done:
Pin 20 has 13.3 VDC
Pin 21 has between 4.1 VDC and 10.8 VDC depending on the dimmer setting
Pin 22 has continuity to ground
These three are 'as designed' in my opinion - so the proper stuff is at
least getting to the DPU.
Is there something that I can check on the cable between the DPU and the
display?
I've sent a note to Vision Microsystems - I'll post their
response.........
Ralph Capen
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bakerocb
Joined: 15 Jan 2006
Posts: 727
Location: FAIRFAX VA
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| Posted: Mon Jul 17, 2006 11:35 am Post subject: VM1000 light system failure |
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7/17/2006
Hello Ralph, Obtaining the right replacement ribbon cable and the proper
connecters was a little tricky because parts from the supplier to VM were
not available. Went out of business or was bought out. I did some research
and came up with equivalent parts from Mouser.
1) The 26 wire IDC (Insulation Displacement Connector) flat ribbon cable
made by 3M that could be bought by the foot was Mouser part number
517-3365/26FT. It was $1.65 per foot.
http://www.mouser.com/search/ProductDetail.aspx?R=3365%2f26-CUT-LENGTHvirtualkey51750000
2) The socket type connectors were Mouser part number 571-7462856. They were
$1.18 each.
http://www.mouser.com/search/refine.aspx?Ntt=571-7462856
3) If you buy a replacement display cable from VM (cost $54) the connector
that goes onto the DPU is already installed and the wire folds back over
itself and that fold is held in place for strain relief by a little plastic
clip that slides onto the connectors in 2 above. That strain relief is
Mouser part number 571-499252-3. Costs about $0.20 each.
http://www.mouser.com/search/ProductDetail.aspx?R=499252-3virtualkey57100000
Please keep us informed of your progress.
OC
PS: My problem started when one of the connectors on the original display
cable from VM had a hidden slight bend in one of the insulation displacement
prongs. When I squashed that connector into place on the cable at the proper
location for one of my VM instruments the prong went slightly sideways and
cross connected the AC supply wire for the lights and the ground wire.
Finding that problem and correcting it was difficult and expensive. (Could
have been even more expensive if not for the gracious help of VM). That is
why I recommend that after assembly every wire on every socket of that IDC
cable be checked on the bench for continuity and no cross connection before
the cable is installed in the airplane.
---
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