HIOKI RM3544-01 Unable to start - Page 1
Forum section: electronics / repair

author: 晓看风云
author_rank: Contributor
timestamp: November 07, 2023, 08:38:34 am
content: I have a HIOKI RM3544-01 that cannot start. Its fault is that it is connected to the power supply, and the power indicator light will randomly light up, but the light it emits is weaker than the normal machine (I cannot determine).When I opened the machine casing and after inspecting many places, I found that if I plugged in the PFC flexible cable, the 3.3V power supply capacitor of the ARM chip on the main control board PCB was in a short circuit state at both ends, which caused the supply voltage of the ARM chip to be almost zero and the machine could not start normally.After I removed the cable from the display board PCB, there will be a beep (there is a buzzer on the back of the PCB) when the main control board PCB is connected to the power supply. I believe that the instrument has started normally.When I was delighted with this discovery, I thought there was a short circuit. Unfortunately, when I was searching for the circuit, I found that the PCB design was like this, as if this short circuit should exist like this.I want to clarify now:1. Is the connection between Pin48 and Pin46 of the PFC cable holder on the main control board GND.(On my circuit board, they are 0 Ω with GND)2. Is there a physical connection between Pin50 and Pin49 on the PFC cable base of the main control board.Is there a physical connection between Pin50 and Pin49 of the PFC cable holder on the display board.(They are measured as 0 Ω on my circuit board)3. Is C144 on the main control board in a short circuit state after connecting the PFC flexible cable?(This board is short circuited after being connected to the PFC, which I am very, very puzzled about because the wiring direction I found indicates that they should be short circuited like this, WTF???)I really need help, I don't know if anyone else has encountered similar problems. I searched the forum and couldn't find any repair information.

author: Swake
author_rank: Frequent Contributor
timestamp: November 07, 2023, 08:50:20 pm
content: Have no idea if this is the case here but this is a possibility:Thismightbe a way for them to detect that there is a display board connected or not.If different versions of the display or main board exist it might be indicated using different shorts so the controller 'knows' how to handle it.

author: 晓看风云
author_rank: Contributor
timestamp: November 08, 2023, 12:22:59 am
content: Thank you very much for your help! Your viewpoint is very correct! Two hours after posting this post, I suddenly realized a problem, is it that the two PCB boards do not match at all. After a long search, I found several images to support my discovery.This machine seems to have undergone facial replacement surgery, hahaha! This sounds simple, but it took me a few days to finally confirm the issue from the beginning of repairing this machine.Carefully observe the attached images I sent, and at the positions I marked, they are different from my instruments. After these three pictures, I can roughly confirm that my machine motherboard is RM3544, while my display screen is RM3544-01.

author: Swake
author_rank: Frequent Contributor
timestamp: November 08, 2023, 07:07:18 am
content: Well.... That is a next level puzzle...I'm sure those board versions have confused the repair people at Hioki themselves especially because the differences are not at all obvious.In the new picture named 1.jpg something strange is going on with the red and black wire. These are soldered directly to components in the middle of the PCB.Have been looking up some things to find the differences in the 2 models and it is not much: Apparently the -01 model is the same with only an additional I/O. Datasheet:https://www.nubicom.co.kr/download/download.jsp?file_name=/hioki/rm3548.pdf. Therefor I would think these 2 meters have the same front end/display.

author: 晓看风云
author_rank: Contributor
timestamp: November 08, 2023, 07:21:21 am
content: Yes, I don't think there have been any changes to the screen, mainly in the PFC cable base. The biggest difference is the position of GND, one on the left and one on the right. So it causes a short circuit when connecting the flexible cable. I am surprised that even with various short circuit connections like this, the motherboard still seems to be in good condition, and there is even a prompt sound when turned on. Thank you again for your help!

author: Swake
author_rank: Frequent Contributor
timestamp: November 08, 2023, 07:51:20 am
content: QuoteWould it have been 180° rotated? That would have required a complete rework of the PCB, which is very strange, but I have seen crazier things already.

author: 晓看风云
author_rank: Contributor
timestamp: November 10, 2023, 01:04:23 am
content: I found more pictures showing red and black lines, which should be connected to external switches, possibly foot switches or more convenient switches for operation.