Help me repair  Inverter MASTERVOLT sine 24/1800 - Page 1
Forum section: electronics / repair

author: AlexB
author_rank: Contributor
timestamp: February 16, 2021, 12:37:35 pm
content: Hello allPlease 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.jpghttps://snipboard.io/LWsMCG.jpghttps://snipboard.io/nGVDxr.jpghttps://snipboard.io/pFNHt3.jpgThank you for any helpPS: 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.

author: madires
author_rank: Super Contributor
timestamp: February 16, 2021, 01:44:17 pm
content: Based on the pinout, L201 between pins 4 and 5 and the compensation network at pin 1 it could be something like an LM2577.

author: AlexB
author_rank: Contributor
timestamp: February 16, 2021, 05:11:24 pm
content: I don't know any power IC step-down similar to LM2577.LM2577 is step-up.

author: AlexB
author_rank: Contributor
timestamp: February 16, 2021, 05:34:09 pm
content: NJM2367 could be a good match, but I'm not sure.

author: CJay
author_rank: Super Contributor
timestamp: February 16, 2021, 05:52:48 pm
content: LT1071

author: fzabkar
author_rank: Super Contributor
timestamp: February 16, 2021, 06:57:34 pm
content: 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.

author: AlexB
author_rank: Contributor
timestamp: February 17, 2021, 04:02:17 pm
content: The nominal input voltage is 24 V.I need buck converter, not boost.

author: madires
author_rank: Super Contributor
timestamp: February 17, 2021, 05:57:37 pm
content: 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.

author: AlexB
author_rank: Contributor
timestamp: February 17, 2021, 07:41:17 pm
content: indeedThat 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

author: fzabkar
author_rank: Super Contributor
timestamp: February 17, 2021, 08:24:12 pm
content: I don't understand how L202 works. It doesn't seem to be in the right position.

author: james_s
author_rank: Super Contributor
timestamp: February 17, 2021, 08:33:24 pm
content: 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.

author: AlexB
author_rank: Contributor
timestamp: February 17, 2021, 10:25:23 pm
content: 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