Help me repair Inverter MASTERVOLT sine 24/1800

[AlexB]

Hello  all


Please help me.


I want to repair  a  MASTERVOLT sine 24/1800  inverter.

But someone desoldered  a  Power IC  and  I don't know what IC was there.


Minimum  safe  input voltage is 36 V  or  better 40 V.

IC204 is the marking on the PCB.


I  also drew a  schematic.   The  five circles  are the IC pins.

The output voltages  are +12 V,  - 12 V  and  again +12V for two fans.


I  searched  a  lot on  the  internet  but  I couldn't find  any  match.

I  can  use  a  reversed pinout  IC.  It doesn't  matter if pin 1 is pin 5  and pin 2  is 4.



Pics:

https://snipboard.io/vo6zw0.jpg

https://snipboard.io/LWsMCG.jpg

https://snipboard.io/nGVDxr.jpg

https://snipboard.io/pFNHt3.jpg




Thank you for any  help



PS:  I  also need  a  user  manual  if  anyone  has.

PS2:  I  will  probably  use  a  separate SMPS,  but  I  wanted  to  try  and  use  the original  circuit.

[madires]

Based on the pinout, L201 between pins 4 and 5 and the compensation network at pin 1 it could be something like an LM2577.

[AlexB]

I  don't  know  any  power  IC  step-down  similar  to  LM2577.

LM2577  is  step-up.

[AlexB]

NJM2367   could  be  a  good  match,  but  I'm  not  sure.

[CJay]

LT1071

[fzabkar]

ISTM that both the -12V and +12V supplies are operating in boost mode, in which case both the LM2577 and LT1071 would appear to be suitable candidates.

[AlexB]

The  nominal  input  voltage  is  24 V.

I  need  buck converter,  not  boost.

[madires]

In case of a simple buck converter the inductor would be between the switching pin and output filter, not between input and the switching pin.

[AlexB]

indeed

That  is  why  it  seems  to  me  that  it  was  a  linear  regulator  which  was working  in a  switching  way.


Do  you  think  I  might  have  measured  one  of  the  IC  pins  incorrectly  ?

If  so,  which  one  ?


The  PCB  has  multiple  layers  and  I  can't  see  all  the  traces.


Thank you

[fzabkar]

I don't understand how L202 works. It doesn't seem to be in the right position.

[james_s]

It's a longshot these days but Mastervolt still exists, have you tried contacting them? If you can manage to reach the right person they may be willing to tell you what the missing part is.

[AlexB]

It  didn't  even  cross  my  mind contacting them on this  matter.     But  thanks for the idea,  I will give it a shot.


I  will  also  desolder L202  so that I  rule out the possibility of false readings...

When checking which goes where I relyed on path of lower  resistence  (the higher resistence meaning it goes through the inductor).


Thank you