e550vl turns on 24v going to inverters fluctuates

[kornwood]

Re: e550vl turns on 24v going to inverters fluctuates

zenar diode is only supposed to read one way right

[cheapie]

Re: e550vl turns on 24v going to inverters fluctuates

zenar diode is only supposed to read one way right

One way up to a certain voltage, and both ways at a higher voltage.

I have a TV with bad 12V caps causing the 24V to be low for some reason...

[budm]

Re: e550vl turns on 24v going to inverters fluctuates

There are two large brown lytics caps (C801A, 801B) rated at 450vdc (they are connected in parallel), check the DC voltage right at the two legs, it should have about 170vdc when TV is plugged in, then it should go up to about 380vdc (due to PFC Voltage booster circuits) when you turn the TV on.
Just be real careful since you will be measuring the voltage on the HOT (deadly) side of the circuits, do not touch anything with your hands.

[budm]

Re: e550vl turns on 24v going to inverters fluctuates

OK, I just trace out the board, the 24V, 18V, 12V are generated by the same drive circuit which drive the main transformer T601.
So you need to see if the 18VDC at CN204 PIN 3&4, and the 12VDC at CN201 PIN 8~10 are also going up and down.

[kornwood]

Re: e550vl turns on 24v going to inverters fluctuates

yes I have 18v and 12v
when pson goes high

[budm]

Re: e550vl turns on 24v going to inverters fluctuates

But are they steady?

[kornwood]

Re: e550vl turns on 24v going to inverters fluctuates

yes there steady but im starting to think its the inverters
just plugged them in and no 24 volts until I unplug the power then voltage shows up and with them unplugged 24v shows up then goes down and the clicks are different too as I plug the power plug in

[budm]

Re: e550vl turns on 24v going to inverters fluctuates

Here is the diagram of the 12v, 24v, 18v power supply section. As you can see, they are all generated by the same transformer T601. The 24v should be steady when you disconnect the load by removing connector CN203.
There are 5 resistors (R254A~E) (connected in parallel) in series which goes out to the load. check the resistance of the resistors.

[kornwood]

Re: e550vl turns on 24v going to inverters fluctuates

if I remove the cable going to both inverters the 24v shows it self but drains but probally because it turns off when it senses no inverters and tjeres no resistors in those locations

[kornwood]

Re: e550vl turns on 24v going to inverters fluctuates

and if I put a probe on a ground on either inverter both outputs go ground on both boards

[budm]

Re: e550vl turns on 24v going to inverters fluctuates

I see them, they are really low Ohm current sensing resistors to shutdown if the load draws TOO MUCH current, so it should not shut down when inverter boards are not connected, if it reallly shutdown, you will lose the 12v and the 18v also since they are driven by the same transformer, it cannot shutdown the 24 section only. There are two resistors (R252, R253) for loading the 24V if the the inverter are not connected.
So it does not make sense that the 24V goes down when inverter is disconnected since it always has the load resistors connected all the time also.
Do you have 2 small 12v bulbs that can be put in series and then connect then to the 24v output so you can see if the bulbs will be fluctuating?
D250A/B, 251A/B should also be checked.
Right now the condition you are indicating does not make sense at all.
By the way, did you check the voltage on the big caps yet?

[kornwood]

Re: e550vl turns on 24v going to inverters fluctuates

ok the big ones read 163 turned off and it goes to 401 when turned on and drops back to 163
thats with inverters unplugged
D250A/B, 251A/B the center pins go to 24v and all other pins beep when I touch heatsink
(R252, R253) those are not there

[budm]

Re: e550vl turns on 24v going to inverters fluctuates

"ok the big ones read 163 turned off and it goes to 401 when turned on and drops back to 163" That means the PFC goes into shutdown.
At the same time the PS_ON is maintained > 3V when the 401V goes back down to 163V?

[tom66]

Re: e550vl turns on 24v going to inverters fluctuates

Have you mentioned yet how much it fluctuates by?

Also, the 24V draws by far the most power and the 12V/18V can be quite light in power consumption. If an over-current limit occurs on the 24V that would drop like a rock while the 12V/18V may drop by comparatively little, enough that you may not immediately notice.

[kornwood]

Re: e550vl turns on 24v going to inverters fluctuates

the 24v drops to 0 like a rock

[tom66]

Re: e550vl turns on 24v going to inverters fluctuates

There's a chance it's a cold solder joint on the 24V output, or on one of the diodes. How often does it drop? Once, twice, every N seconds?

[kornwood]

Re: e550vl turns on 24v going to inverters fluctuates

it drops everytime i try to turn it on only comes back if i turn off then back on it will show again but drop like before

[tom66]

Re: e550vl turns on 24v going to inverters fluctuates

And the 12V, 18V are always good?

[kornwood]

Re: e550vl turns on 24v going to inverters fluctuates

12V, 18V stay on strong always

[tom66]

Re: e550vl turns on 24v going to inverters fluctuates

OK, I would suggest getting two automotive headlights, tying them in series and putting them across the 24V output, with the inverter disconnected. This will show if there is a fault on the inverter or PSU.