Hi,
I just imported a few high brightness monitors from China for Teleprompting and they are great, except for one strange problem.
When I plug in the AC/DC adapter and turn the brightness above 74, the screen suddenly flickers. There is zero flickering below 74 and then really bad flickering at 74 and above.
Below is a picture of the AC/DC adapter

(Incidentally, I tried plugging in an AC/DC adaptor like the above rated for 5amps instead of 3amps and the adaptor flashed slowly and the monitor did not power up at all.)
Now, here's the strange thing. I plugged in a battery I happen to have for these monitors and it powered up perfectly and exhibited no flickering at all at any brightness level.
Here are the relevant specs for that battery:
"The Bescor FP-12VATM 12v Lithium-Ion Battery Pack operates between 11.1 and 12.6VDC and features a 98Wh capacity. The charger provides an output of 12.6V and 2500mA."
Anyone have any idea why this might be? Any suggestions for how I can remedy this problem so the monitor can be wall-powered without flickering?
Thank you, kind people for reading and any guidance.

 

It sounds like the adapter voltage is incorrect.
Can you measure the voltage when the monitor acts up?

 

Power supply inadequacy will certainly produce the problems that you describe. AND the supply regulation may not be adequate, either. That might even be caused by poor connections in the output cable, or the connector. I have seen both types of problems.

 

Incidentally, I tried plugging in an AC/DC adaptor like the above rated for 5amps instead of 3amps and the adaptor flashed slowly and the monitor did not power up at all.

Was the connector polarity correct?

 

I will ask to have the polarity checked and voltage while running checked asap.
Till then, could reversed polarity of the wiring to the power explain what we've seen?
ie.
3amp adaptor works at medium brightness, then flickers at higher brightness.
Battery works at all brightness.
5amp adapter doesn't power on
?
I should add, a little light indicator on the 5amp adaptor did flash, as if it were showing some kind of an error.
I will report back with results tomorrow, but I would be curious to know if polarity could be the culprit given the above. (Obviously, I'm not very savvy with electronics).

 

Incorrect polarity could account for the 5A regulator to flash and not work (the monitor input may have a diode to ground on the input for reverse polarity protection, which would look like a short to the regulator).

But that doesn't explain the first regulator problem.
To check that, you will need to measure its voltage under load.

 

known problem.
output impedance power supply to high.
result: at a certain load voltage drops then current will follow voltage goes up.
output is oscillating at a low frequency defined by its load.
advice replace power supply and add an integrator ( cap X00 uF with 0.1uf and 10uF parallel)

Capacitor has a direct relation to internal power sup impedance and current.
if flicker rep rate is .1 second you must be able to avoid discharge during that period.( R C time)

Picbuster

 

Incorrect polarity could account for the 5A regulator to flash and not work (the monitor input may have a diode to ground on the input for reverse polarity protection, which would look like a short to the regulator).

But that doesn't explain the first regulator problem.
To check that, you will need to measure its voltage under load.

Perhaps the reverse polarity is the problem. To clarify, the plug is a 4 pin XLR - looks like this:

I know there are only two wire - one connected to each of the pins -one wire to pin #1 and one wire to pin #2. My question is, would it be possible for the wires to be reversed (and the polarity is reversed) - for the monitor to still power on?

 

Sounds like the 3A supply runs out of steam gracefully when the brightness is high, whereas the 5A power supply thinks the start-up load is excessive so shuts down to protect itself.

 

Sounds like the 3A supply runs out of steam gracefully when the brightness is high, whereas the 5A power supply thinks the start-up load is excessive so shuts down to protect itself.

Yes, sounds right. Could this be related / remedied by the two wires being reversed? (ie. the polarity being reversed?)

 

You should measure the voltage polarity at both power supply's pins.

 

A new 8Amp AC/DC adaptor fixed the problem. Thank you everyone for your input.