Fluke 233 could not start properly - Page 1
Forum section: electronics / repair

author: antyvirusa
author_rank: Newbie
timestamp: January 31, 2023, 08:26:11 am
content: Hello everyone,I am new to the forum, but already read a lot of topics here. My problem is that I recently owned non working Fluke 233 and can not make it to work. When I switch the rotary switch position there is only red led flashing and ---- (four dashes) showing on the display. It did start properly one time and I tested all functions except current measurement and all were working pretty fine, but this happened only one time (maybe I already tried hundreds or thousands times switching it off to VAC- the first function). The thing that I know, whenever it start properly the attached display is showing only dashes and is working only via RF (I think this may be optical problem between the body and the display). When it started properly the red triangle turned off and was not flashing. Anyway whenever I start it now the red triangle flashes and display only shows four dashes, when attached or RF ERR when not attached. The display is only turned off and on by the body when attached.The consumption of the body is surely less than 1mA as my power supply can show mA (I test it with power supply, not with batteries). All resistors on board are tested and in working conditions. Inductors checked for continuity and are okay. No shorted capacitors also. MOVs and current sense resistors are also fine. The rotary switch looking fine and steps with about 0.30V between positions. Voltages +2.5V, -2.5V, +0.8V seems fine also. I already resoldered every pad/pin on the PCB including the microcontroller, ADC (LTFLK2) and RF (13201), also checked for short circuits and there are none. I checked the SPI lines (I think that they are SPI, checking the datasheet of the microcontroller) and are all in HIGH level while in VAC position, no clock, no data I can see on the scope. I also cleaned the board with Isopropyl Alcohol.I think it stuck while booting and could not go on. Maybe waiting for some signal...If anyone could help me, I will really appreciate this. And if someone could tell me if the body could be started without the display attached (the red triangle to be turned off) I will be thankful. As I read in the user manual this is possible and this is not a fault in my research as I switch on and off the body without attached display. Also someone with working Fluke 233 DMM if could measure the test points on the board will be a big help. I attach PCB pictures (the burned looking paths are from very bad flux that I can not clean).

author: sunfire
author_rank: Contributor
timestamp: January 31, 2023, 03:18:21 pm
content: /deleted

author: Ugur
author_rank: Regular Contributor
timestamp: February 02, 2023, 05:56:29 am
content: Most likely your problem is with the video card.Did you change the batteries of the display?If yes, is there any bad contact or oxide on the board?You can freshen the solders.The optical sensors in the display module may be faulty.This problem should not be caused by the motherboard, have you had the opportunity to try with another screen?

author: antyvirusa
author_rank: Newbie
timestamp: February 02, 2023, 06:09:04 am
content: Quote from: Ugur on February 02, 2023, 05:56:29 amThank you very much for the reply.What do you mean with the video card (what is video card here)?Yes, already changed the batteries, also tried on external power supply. I know for the battery leakage problem with older firmware (mine is v1.1).I freshened MCU solders, but still nothing.The optical sensor is probably faulty and I will check these, but I think the body should start without display and the red high voltage triangle should switch off when MCU boots properly and ready to make measurements??Unfortunately I could not find someone with the same DMM in my area to check with another display..

author: antyvirusa
author_rank: Newbie
timestamp: February 02, 2023, 06:27:46 am
content: Another thing that I forgot to update is that I found that pin 70 - MOSI pin (probably used for SPI, as it have connection with a pin of the external ADC) is floating. Whom is the responsibility to pull this pin - the master or the slave? (I think maybe the slave should pull up this pin after low level on CS and then master's output should drive this??) All other SPI pins (CS, MISO, CLK) are logical high in the same time and I can not see any transitions in any way. Any help will be appreciated.

author: srmahaffy
author_rank: Contributor
timestamp: February 03, 2023, 04:20:16 am
content: Hi,I’ve purchased about four broken Fluke 233 meters and repaired/ resold them. I think the first thing I’d check on your meter, is to look at the window on the plastic housing of the display and base unit. On the last meter I repaired, it had a couple of open traces because of battery corrosion, but, after I repaired those, I tackled an issue where it worked when the base was disconnected (remote mode), but not when it was connect to the base. After further inspection, I discovered the plastic window on the display unit for the rf signal to pass through was partly eaten /corroded from a chemical or something from the previous owner, which prevented the signal to pass through. Regarding the test points, I attached some notes (scribbles) of when I was doing some of my troubleshooting/testing of past meters. Maybe it will help you. Where there is red ink, those were measurements of bad voltage readings. The black ink, is good voltage readings.I agree with you, about seeing the red dashes, and red LED staying on, that it hasn’t booted up completely. It doesn’t sound like the cause is any of the M430F449 chips. Your PCBs look pretty clean too.Another thing to check is the voltages at DS202. One side should be tied to the “-“ PCB terminal, and the other should read about 35mV. ( I had another 233 meter where the lead that connects to the “-“ PCB terminal was open, which caused dashes). All my voltage readings were referenced to the “-“ terminal on the PCBs.Keep us posted of your progress

author: srmahaffy
author_rank: Contributor
timestamp: February 03, 2023, 04:42:16 am
content: Hi, I think I made a reference designator error on my notes for the Display unit, and in my previous post. DS202 might be O202 (?). It’s the white part to the left of O204 that sits partly under the “-“ negative battery terminal on the PCB. both the white parts are for the transmit and receive of the remote circuit between the base and display.

author: antyvirusa
author_rank: Newbie
timestamp: February 03, 2023, 01:36:26 pm
content: Quote from: srmahaffy on February 03, 2023, 04:20:16 amHello, Thank you very much for the response. It was really DS202's negative terminal. Although I am sure I checked it before, today when I checked it again, there was no continuity and it was the cause. And whoala, it is working now with attached display.BUT another problem occured . Wireless transmission is not working. It is possibly caused by me after several desoldering and soldering the RF IC(because its contacts looked oxidized to me and I saw that they are not soldered well (this is only mine opinion)). Here is what is the situation now:I measure 35mA to 45mA current of the display module while trying to establish connection;In the same time there is no more than 1mA current consumption on the base unit;In the base unit I can see, that after detach the display the SPI communication is started (there are MOSI, CLK and CS transitions). Also RST pin goes high. No transitions on MISO pin! The whole process takes about 1 to 2 seconds and RST is again held LOW and no more SPI transitions.So in this situation probably I think the RF IC of the base unit is damaged, as it not responds to SPI master via the MISO pin. I also checked its input voltage and there is 3.3V. I did already purchased the RF IC when I received this DMM, so now waiting for it...If you have any advice I will really appreciate this.Once again thank you very much for the help.Greetings from Bulgaria.

author: srmahaffy
author_rank: Contributor
timestamp: February 04, 2023, 02:56:06 pm
content: Hi, I think it’s best to wait for your replacement part and see how things work after you replace it.Can you share the part number you purchased?It sounds like you decided to reflow the solder of the two white rf parts on the base unit before seeing how everything worked after you repaired the DS202 “-“ battery terminal. Is that correct?Does the meter still work when the display is attached to the base unit?I purchased a broken Fluke 233 recently and I’m still waiting for it. I don’t know the state it will be in, and know the base unit is not working. I also happen to have a spare base unit PCB. With everything, I could possibly use it to make some measurements for you.What does the meter show when trying to use it in remote mode? Does it show dashes and the LED staying on?Thanks

author: antyvirusa
author_rank: Newbie
timestamp: February 04, 2023, 03:10:49 pm
content: Quote from: srmahaffy on February 04, 2023, 02:56:06 pmHi,the part that I purchased is the RF IC with designator U104 on the base unit PCB. Its part number is MFC13201. This is the part I soldered and resoldered several times.The two white parts are not RF parts, and they are IR emitter and receiver. They are working fine. After your advice to check DS202 negative terminal, I found that this is the actual issue. Thank you once again for this.Now the DMM works fine with attached display unit.When in remote mode it shows dashes and the red light stays on.For now I will wait for the RF IC. As I can not see any current consumption on the base unit while trying to establish connection, I think it never tries to pair with the display unit. Probably the RF IC is damaged.It will be helpful if you can check the MISO pin of the U104 if there are any transitions in remote mode. Thanks in advance.

author: srmahaffy
author_rank: Contributor
timestamp: February 04, 2023, 03:46:52 pm
content: Hi, thank you very much for the clarification, and helping me gain more depth of the circuit.I knew the white parts were IR TX/ RCV parts, but generically used RF wording.I’ll keep you posted on measuring the MISO pin of U104.Have a great day!

author: srmahaffy
author_rank: Contributor
timestamp: February 26, 2023, 02:56:17 am
content: Hi,Sorry for my delay in posting back. I was able to measure the Fluke 233 that I purchased and got working. (Easy fix, with a missing battery contact, and one broken one….). The MISO pin on U104 of the MC13201 chip, (pin 18), is about 5 mv when the meter is in the off position and while in the non remote mode (when the display is attached to the base). When the meter is in remote mode (display is detached from the base), the MISO pin fluctuates up and down between 15 - 36mv.I hope this helps. I didn’t use a scope, and just measured in DC volts using my Fluke 87V, with its com port connected to the “- “ battery terminal of the Fluke 233Keep us posted on your meter.Sincerely,

author: antyvirusa
author_rank: Newbie
timestamp: February 28, 2023, 02:13:36 pm
content: Hi again. There is some update on this issue and hope it will help others with the same problem.In my previous post I wrote that there is no current consumption while in remote mode, but after I leave it for a day without use the batteries were totally discharged. So I measured again and then there were 60mA constant current consumption in both remote and with display attached. It still made measurements right and working but with this constant current consumption. Then I desoldered the RF IC and the current consumption was again less than mA in sleep mode.I recently received the RF IC that I already purchased (more than a month waiting for it) and soldered it. Now everything works like a charm in both remote mode and with attached display. Current consumption is normal and no more dead batteries.Thanks to everyone that helped me.Hope this could help more people with similar problems.

author: srmahaffy
author_rank: Contributor
timestamp: February 28, 2023, 04:05:41 pm
content: Great job repairing your meter!!!I wanted to share about the current drain on some of the earlier Fluke 233’s even when they are turned off. Attached is from the Fluke website. They recommend removing a battery from each compartment when not in use.

author: antyvirusa
author_rank: Newbie
timestamp: February 28, 2023, 04:38:00 pm
content: Quote from: srmahaffy on February 28, 2023, 04:05:41 pmThank you!I am familiar with this problem and will check how much time will last the current pair of batteries. I know this issue is solved in newer firmware versions after ver 1.01 for Fluke 233. Unfortunately mine is v1.01 and will use it in this way. It is great that it is working just like have to be.