ROM / firmware for Philips PM6303 LCR meter - Page 1
Forum section: electronics / repair

author: giosif
author_rank: Frequent Contributor
timestamp: November 27, 2017, 06:01:35 pm
content: Hi,I've recently scored a broken PM6303 LCR meter which, by the looks of it, has either a dead CPU or a corrupt ROM.I am working on getting a replacement CPU but, in the meantime, I was wondering if anyone has a backup of the ROM from their PM6303 meter.Please note I am talking about the PM6303 model and NOT its younger brother PM6303A.Thanks!

author: picburner
author_rank: Frequent Contributor
timestamp: November 27, 2017, 06:10:14 pm
content: http://www.ko4bb.com/getsimple/index.php?id=manualsLook for Fluke PM6303

author: giosif
author_rank: Frequent Contributor
timestamp: November 27, 2017, 07:01:35 pm
content: And I wanted to check that site before posting the question here but, for the life of me, I could not remember the name of the site.Thank you!Turns out the checksum matches that of my ROM backup.So, likely the CPU is dead.While the replacement is on its way, I should try to understand why the existing CPU died in the first place.

author: Samogon
author_rank: Frequent Contributor
timestamp: February 05, 2018, 06:32:40 am
content: CPU as i know it has microcontroller most likely is alive. Did you check clock and reset pin state? What about activity on address pins?

author: Armadillo
author_rank: Super Contributor
timestamp: February 05, 2018, 06:49:32 am
content: I have rarely seen dead microcomp.This thing uses discreet external crystal clock oscillator.You should probe the D306 74HC393 instead for the clock.

author: giosif
author_rank: Frequent Contributor
timestamp: February 05, 2018, 10:57:18 pm
content: Thanks, guys!A bit puzzled by the timing of your responses (my previous message on this thread was back in November...) but, in any case, it looks like it was the CPU.I put in the replacement CPU and the meter started to show signs of life.That said, I'm not ruling out the possibility the initial CPU may still be ok and it was just some corrosion/bad contact.Anyways, I've since managed to break the LCD, then came up with an Arduino + character LCD replacement.The rest of the adventure is told here:https://www.eevblog.com/forum/repair/help-troubleshooting-pm6303-lcd-display-issue/msg1370578/#msg1370578

author: Samogon
author_rank: Frequent Contributor
timestamp: February 06, 2018, 03:21:48 am
content: Quote from: giosif on February 05, 2018, 10:57:18 pmHe he, i was repairing PM6303A and was googling for repair info. And found this thread.

author: Armadillo
author_rank: Super Contributor
timestamp: February 06, 2018, 04:18:09 am
content: kkkkkkk, I think how did you came to the conclusion of the faulty CPU will be interesting in the repair forum.

author: giosif
author_rank: Frequent Contributor
timestamp: February 06, 2018, 06:49:19 pm
content: Quote from: Samogon on February 06, 2018, 03:21:48 amGot it.Well, if you ever get fed up repairing that unit and don't know where to throw it away, I'd be happy to provide it a nice "rehab" space.

author: Samogon
author_rank: Frequent Contributor
timestamp: February 06, 2018, 06:58:01 pm
content: It was repaired successfully. Will write short story later

author: giosif
author_rank: Frequent Contributor
timestamp: February 06, 2018, 07:05:11 pm
content: Quote from: Armadillo on February 06, 2018, 04:18:09 amWell, I had bridged link D on the board and that was supposed to get the meter to loop through a diagnostics sequence.However, nothing resembling a sequence was showing on the display, but rather something of a static, undiscernable kind of content (might have been blinking rapidly, but nothing looking like a cycling through a sequence).I then checked voltages and clock signal and they were both fine.I believe I have also removed and reseated the CPU and ROM IC's.I might have done other checks too, but can't remember any others at the moment.So, at that stage, the CPU IC was one of the potential causes of the behaviour (along with other candidates).Then, checking on our favourite online auction site, I found a replacement IC that wasn't discouragingly expensive and I thought I can give this theory a try without considerable additional cost.Once the replacement IC arrived and placed it in the original IC's place, I could immediately see a change in behaviour, more towards what I was expecting the meter to do.

author: giosif
author_rank: Frequent Contributor
timestamp: February 06, 2018, 07:12:03 pm
content: Quote from: Samogon on February 06, 2018, 06:58:01 pmOh shoot!Err... I mean "Well done!"

author: Samogon
author_rank: Frequent Contributor
timestamp: February 06, 2018, 11:12:32 pm
content: OK short repair story.Got Fluke MP6303A from unnamed auction site. It was not showing anything on the screen, just back light is on.1. Check all power rails +15 -15 +5 -5 are all ok.2. Check clock, it is OK.3. Check micro controller activity, well all pins are high. Why? Because its reset command is high. Reset comes to CPU using NAND element of D308.And i found that no matter what its pin 13 always low, aha! lets go check why power reset line always lowAll good except C420, it has high ESR 1.5 Ohm and it was pulling reset signal down. Changed C420 and we have excellent bench top LCR meter, the only limitation that it has 1kHz upper limit, all modern handhelds have 100kHz, but precision still unbeaten.Here are my repair route in pictures.

author: giosif
author_rank: Frequent Contributor
timestamp: February 09, 2018, 11:42:25 am
content: Quote from: Samogon on February 06, 2018, 11:12:32 pmCool!The way you tell it, it sounds like a quick, direct fix.And it may have been like that in your case, but I know I can spend hours for something that sounds like minutes when I tell it here.

author: Samogon
author_rank: Frequent Contributor
timestamp: February 09, 2018, 01:34:14 pm
content: Well total spend approximately 3-4 hours over few days.

author: giosif
author_rank: Frequent Contributor
timestamp: February 09, 2018, 01:57:15 pm
content: Quote from: Samogon on February 09, 2018, 01:34:14 pmAh, ok, so not exactly "instant fix", then.

author: brokenslinky
author_rank: Newbie
timestamp: February 23, 2021, 01:18:53 pm
content: Quote from: Samogon on February 06, 2018, 11:12:32 pmThanks for the troubleshooting guidance, Samogon. I was able to pick up a nearly dead 6303A for $50. It was behaving quite similar to yours. Tested the supplies and started probing the processor. Confirmed the RST was stuck high. Immediately swapped out C420, powered it up and it started breathing again. Spent a couple hours poking around inside, making sure nothing else was ready to flake out. Ordering in some tighter tolerance resistors and capacitors to do some performance testing but so far it looks like its doing what its supposed to. Now to forget to discharge a big electrolytic cap and blow the input side of the thing up.