CE Pro March 2024 - 24

Networking+Home Control
HDMI CORNER by DPL Labs
AOC/AVR Replacement
Resolves Tricky Power
Supply Problem
DPL LABS has been working
with many major AVR and
display companies helping
them work out AOC (active
optical cable) functionality
issues since late summer
2023. During that period,
approximately 14 additional
issues were identified. They
range from power supply
management to input/output
ratio levels, and some
high-speed properties that
require tighter tolerances.
Most recently, another
failure was brought to our
attention. It involved a new
30-meter AOC that came
stock with both source and
display power supplies to
guarantee its power and stability.
It's a great idea, maybe
a bit over the edge, but still
nice for the integrator.
It falls under power
management again, but this
one was a real doozy. We
received just one sample
of this device, but it was
at least a way to find out
where the problem was.
The integrator installed
the device with its external
power supplies and
received no response. He
then removed the supplies
and tried it again. There was
no improvement. He finally
replaced the device with
another of the same make
and model. Again, the unit
did not respond.
24 | CE Pro March 2024
The integrator finally
replaced the AOC with a
different make and model
only to find out the
problem still existed. That's
when DPL got involved. We
instructed the integrator to
replace the AVR and AOC at
the same time as an experiment,
which he did, and the
system came to life.
So, what causes this to
happen and how can it be
used the external supplies,
the AVR was not affected.
But when he used it
again without the external
supplies, it forced the AVR
to pick up all the supply
current. When measuring
the supply current of just
the AOC, it was found
to be pulling over 1 Amp
of current taking out the
AVR's HDMI supply. Now
with a down AVR when a
" The integrator was running
in circles since this second
try with the original AOC
caused the AVR failure to occur
early on in his troubleshooting. "
prevented? We asked that
the first AVR be sent to us
along with the original AOC
that did not work, giving us
all the samples and tools we
needed to diagnose the real
issue. It turned out that the
AVR's HDMI supply voltage
was non-existent.
Why and when did that
occur? Tests uncovered
that the original AOC used
with the external power
supplies was the problem.
Even though it employed
external supply components,
removing these for
the second attempt was
fruitless. Since the first try
different branded device
was implemented, it had no
way of functioning without
the AVR's HDMI supply.
By changing out the AVR
and the AOC for the third
attempt, all was good and
the system responded.
What did we learn? Due
to the chain of events that
occurred, the integrator
was running in circles since
this second try with the
original AOC caused the
AVR failure to occur early
on in his troubleshooting.
Remember that the
supply current required
by HDMI is only .055mA.
Many sources provide
more than that but, in this
case, the AVR would have
needed a beefy supply of
better than 1.5 Amps to
be able to survive the high
current load inflicted on
it from the first AOC with
no external supply. At that
point, the damage was already
done and no matter
how many times he tried
it was only when the AVR
was replaced when things
fell back into place.
Further studies on the
high-current AOC were
conducted at the frontend
electronics (source
side) internal power supply,
finding exceptionally
high current demand. Why
the supply did this is still a
question. By dissecting the
source headshell, we were
able to run an external
supply to the device to
see if the VCSELs would
even operate and they did.
So, the problem was in the
AOC internal regulators
from the start - maybe
designed with too low of
a required supply current.
This could have been
caught way before this
integrator got stuck.
JEFF BOCCACCIO,
president of DPL Labs, can
be reached at info@dpllabs.
com, or visit dpllabs.com.
cepro.com
http://www.dpllabs.com http://www.cepro.com
CE Pro March 2024

Table of Contents for the Digital Edition of CE Pro March 2024
