M-Audio powered speaker turn on problem

[Bigdrums]

Have a pair of M-Audio GSR10 powered PA speakers. They refuse to turn on with power switch, but when I ramp them up on the variac they come on normally and work correctly. Any suggestions why?

[doctor]

It is really strange that two devices have the same fault.
The easiest way is to turn on the device through the variac and to measure the voltages at several points at
the input of the power source and inside. Then turn it on without variac and see what voltages have changed.
Analyze and try to find the cause. It may take several attempts. The task is complicated by the fact that the
type of the power source is SMPSU.

[Enzo]

Many SMPS have a soft start, like a low resistance with a shorting relay. Possible that using the variac fools the soft start circuit.

[doctor]

This SMPSU uses NTC, not shorting relay.

[Enzo]

NTC is another way to do it, yes, but I have rebuilt enough Behringer SMPS with a relay shunting resistors in that function. We don't seem to have a schematic here, so I believe you, but we are limited in the help we can supply.

[nosaj]

NTC is another way to do it, yes, but I have rebuilt enough Behringer SMPS with a relay shunting resistors in that function. We don't seem to have a schematic here, so I believe you, but we are limited in the help we can supply.

A timing issue? variac bringing it up slowly?

Check to see if there are any part numbers on the board sometimes we can find schematics based on those.

nosaj

[Bigdrums]

[Bigdrums]

I ordered new thermistors used for inrush current limiting hoping that will solve the problem
Keep ya all posted

[nosaj]

[ATTACH=CONFIG]53998[/ATTACH]

Does board look similar to this?

https://www.fullcompass.com/prod/238...ply-pcb-for-k8
nosaj

If so maybe this will help
http://bee.mif.pg.gda.pl/ciasteczkow...Schematics.pdf

[Bigdrums]

I inserted the wrong pic, here are 2 of the M Audio board:

[J M Fahey]

I guess "not using a Variac" does not imply "using a lightbulb limiter instead"
Just checking.

[Bigdrums]

Hey Juan:
You suggested for me to draw a schematic of the Furman Parametric EQ I was working on which I did and posted it.
But I did not hear back from you on it. Could you take a look and see what you might comment on ?
Thanks

[Bigdrums]

Well the thermistors don't help. I have noticed a relay in the PS section that engages when I ramp up slowly, and takes about 5 seconds or so to disengage when the power is cut. If I turn the power back on before the relay disengages, the amp comes up fine. So what ever it is has to do with that relay engaging. Why it doesn't engage when the power is just turned on I have no clue. Anyone?

[olddawg]

Are you monitoring the voltage on the relay? A common problem with protection relays is the contacts “carbon up” and become resistive, arc, or stick.

[Bigdrums]

Are you monitoring the voltage on the relay? A common problem with protection relays is the contacts “carbon up” and become resistive, arc, or stick.

The 12v activating the relay is present only when I ramp the power up somewhat slowly on the variac