Replaced PN8024R, but that didn't fix the thing...

 

Replaced PN8024R, but that didn't fix the thing...

Follow post #39

 

Follow post #39

So voltage on these two pins is around 28.8, and it's kinda dancing like 28.7 to 28.8...
So far I replaced diodes, capacitors, the coil, those 2 transistors, that chip... the only thing I didn't replace is that dark green capacitor and that light green inductor, also those two beige resistors, but i checkted them and they are ok...

also I tried Control board on 9V battery ( connected on same pins as where i measured voltage) and it worked, but when i connect it to the board, it just repeatedly beeps... I also tried to connect only those two pins to the board, same issue...

What I see, it's that there is ma voltage for AMS1117 3.3V is 15V, but the pins output ~28V... so could that be the issue, but then, wouldn't AMS1117 just burn out, or break, and the board wouldn't continuesly beep?

 

So I have Gorenje Panel heater "optiheat 2000 ewp" it have 2 boards, control board and power board, and it looks like something on power board went wrong.

This is the continuation of this thread here: Forum Thread

I have attached the photos of the board!

So far I replaced diodes, capacitors, the coil, those 2 transistors, that chip... the only thing I didn't replace is that dark green capacitor and that light green inductor, also those two beige resistors, but i checkted them and they are ok...

also I tried Control board on 9V battery ( connected on same pins as where i measured voltage) and it worked, but when i connect it to the board, it just repeatedly beeps... I also tried to connect only those two pins to the board, same issue...

What I see, it's that there is ma voltage for AMS1117 3.3V is 15V, but the pins output ~28V... so could that be the issue, but then, wouldn't AMS1117 just burn out, or break, and the board wouldn't continuesly beep?

 

What I see, it's that there is ma voltage for AMS1117 3.3V is 15V, but the pins output ~28V... so could that be the issue, but then, wouldn't AMS1117 just burn out, or break, and the board wouldn't continuesly beep?

The regulator could be outputting a low voltage - enough to beep but not enough to do anything useful... or a higher voltage, which means possibly the board is fried and all it can do is beep.

 

The regulator could be outputting a low voltage - enough to beep but not enough to do anything useful... or a higher voltage, which means possibly the board is fried and all it can do is beep.

The control board works fine on 9V battery, that's why I'm confused. But when I connect those 2 pins to the power board it just beeps repeatedly.

 

Check the output of the regulator, is it 3.3v?

 

Check the output of the regulator, is it 3.3v?

Its switching quickly from 10V to 20V

 

Its switching quickly from 10V to 20V

Ouch, you're lucky the downstream MCU etc are still alive, but not for much longer I suspect, that'll be stressing them badly. Clearly the regulator is unhappy with that input voltage; it's in some strange world of its own. You need to check it with a 12v input from a wall-wart or LiPo battery pack that has sufficient current delivery capability, around 1A should do it, to see if it is actually working ok.

 

Ouch, you're lucky the downstream MCU etc are still alive, but not for much longer I suspect, that'll be stressing them badly. Clearly the regulator is unhappy with that input voltage; it's in some strange world of its own. You need to check it with a 12v input from a wall-wart or LiPo battery pack that has sufficient current delivery capability, around 1A should do it, to see if it is actually working ok.

But I can't figure out what the issue is.

so, i have atthed it to around 6V on AC pins..

and here are the measures:
1-2 = 12V
1-3 = 18V
1-7 = 12V
5-4 = 13.5 and slowly climbing
1-6 = 6V

Let me find 12V charger

 

Another thing, When i disconnect board, the volate is climbing to around 12-13 volts on pins 5-4, but when i connect the board its in milivolts... that is on 12V battery charger... So i don't know what is going on...

 

Measure voltages:

X-X on AC volts (>90V expected, take care )

A-G, B-G, C-G on DC Volts (probes as colour shown).
(>90v, >90v, <20v)

 

Measure voltages:

X-X on AC volts (>90V expected, take care )

A-G, B-G, C-G on DC Volts (probes as colour shown).
(>90v, >90v, <20v)
View attachment 363582

Soo, I measured in DC mode:
AG = 328V
BG = 328V
CG = jumping fast between 38V and 48V, like one second its 38V and another its 48, and it jumps like that...
G and pin next to C is 28V

In AC mode:
XX = 237V

 

hmmm - I think one of those capacitors below the IC is breaking down... most likely the green one, but I'd probably replace all three to be sure.

 

hmmm - I think one of those capacitors below the IC is breaking down... most likely the green one, but I'd probably replace all three to be sure.

I replaced all electrolytic capacitors, I don't have replacement for the green one, but I will find it somewhere hope so

 

hmmm - I think one of those capacitors below the IC is breaking down... most likely the green one, but I'd probably replace all three to be sure.

Replaced Green one, its still the same issue, still getting 28V for the control board

 

I have also found this typical circuit for PN8024R:

 

I have also found this typical circuit for PN8024R:
View attachment 363868

Yes, but yours is more like the reference circuit earlier in the datasheet, and exactly the one I drew from your circuit board in post #22

 

Yes, but yours is more like the reference circuit earlier in the datasheet, and exactly the one I drew from your circuit board in post #22

Yeah, I am trying to figure out why is it going above 12V when PN8024R should output 12V, not above it, but im getting like 28V...

 

Yeah, I am trying to figure out why is it going above 12V when PN8024R should output 12V, not above it, but im getting like 28V...

Do you have an LCR meter to measure inductance? The only other reason for the output being wrong, assuming the chip isn't faulty, is a wrong inductor value - maybe it has an internal short.