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AXPERT MKS PLUS DUO 5KW IS DEAD !!!!!


moh

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Hi Guys,

I have a Voltronic AXPERT MKS PLUS DUO 5KW that wont start even when a connected it just with batteries 

I took the main board out and tested the SPS (Switch Power Supply) based on the service manual

and every part of it is working fine I replaced the control card with a new one and it still cant 

start up.

please help me

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4 hours ago, moh said:

still cant start up.

Do you mean you don't see any segments on the LC Display light up?

Do any of the LEDs come on briefly at start-up?

It is possible that the LC Display cable isn't inserted correctly? A classic mistake is to swap the LC Display 4-pin cable and the SCC 4-pin cable. But the LEDs are on a separate cable.

4 hours ago, moh said:

tested the SPS (Switch Power Supply)

So you see roughly 15 V at the point marked +15V-P on this partial schematic trace?

4 hours ago, moh said:

I replaced the control card with a new one

Voltronic Power are notorious for not sending quite the right model of control card for your inverter. Since it doesn't help just now, and since all your settings are stored in EEPROM inside the DSP chip of the original control card, I'd put the original control card back in, at least till you get some signs of life.

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first of all thanks for the quick respond Coulomb.

 I replaced the control card with the original one 

then I made sure to connect the LCD pins correctly still nothing no LCD or LED light 

I tested the SPS based on the link partial schematic trace at the point marked +15V-P 

I took the readings at D57 and D49 and got 0.3 V instead of 15 V 

I replaced them with new still the same readings 

what should I test ?

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10 hours ago, moh said:

I took the readings at D57 and D49 and got 0.3 V instead of 15 V

This is with respect to BAT-? (The cathode of D57 and the anode of D49 should be the same potential.) If so, that's your problem.

10 hours ago, moh said:

what should I test ?

Assuming that there isn't a proper 15 V output, and therefore not a proper 5 V output (I assume that the DSP will operate off the 5 V supply), then check for a square wave (perhaps 14 VAC with a true RMS reading meter) at the output of U10, and make sure U10 has power at pin 7 (anode of D49). All with respect to BAT-, though I can't recall what the 5 V output is with respect to.

There may be a short on one of the power supply outputs; that should be obvious from a resistance measurement with the power off (and allowing time for capacitors to discharge, of course).

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10 hours ago, moh said:

where does the 15 V come from before D49 ?

? From +15V-P, seems pretty clear to me.

Edit2: so it keeps itself powered up after it gets started.

Edit: does pin 7 go high briefly after you turn on the inverter start switch? That's the rocker switch under the inverter-charger.

Edited by Coulomb
Use -> turn on
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21 hours ago, moh said:

pin 7 stays less than 1 V the entire run time 

Well, there's your problem.

Quote

I meant to ask where the 15 V come from...

From Q36 itself. Once it gets started, the power from the switching MOSFET Q36 via transformer (actually a multi-winding inductor) TX9 and diode D57 is vastly more than is needed to power U7. It's a bit incestuous, but it works 🙂.

When the AC Start (main inverter rocker switch) first turns on after having been off for a while, [ edit: and when the battery is first connected, ] should send a pulse of current via C7 into the base of Q9, which should conduct for a second or so, which should turn on Q10 briefly, which should send a pulse of voltage to U7 via R13||R12 and D50. So check that chain of components. Note that the rocker switch has to be off for a while to discharge C7 if you're testing continuously and don't want to disconnect the battery all the time. The time constant for discharging C7 looks to be about 300 ms so leaving the switch off for about 2 seconds should do it. It should charge in about 200 ms, so the pulses won't be really long, so your multimeter won't have time to settle on a stable reading. Perhaps watch the "bar graph" on your multimeter, if it has one, or use an oscilloscope.

Edited by Coulomb
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