ROM / firmware for Philips PM6303 LCR meter

[giosif]

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!

[picburner]

http://www.ko4bb.com/getsimple/index.php?id=manuals

Look for Fluke PM6303

[giosif]

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.

[Samogon]

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?

[Armadillo]

I have rarely seen dead microcomp.
This thing uses discreet external crystal clock oscillator.
You should probe the D306 74HC393 instead for the clock.

[giosif]

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

[Samogon]

Thanks, guys!

A bit puzzled by the timing of your responses (my previous message on this thread was back in November...)

He he, i was repairing PM6303A and was googling for repair info. And found this thread.

[Armadillo]

kkkkkkk, I think how did you came to the conclusion of the faulty CPU will be interesting in the repair forum.

[giosif]

He he, i was repairing PM6303A and was googling for repair info. And found this thread.

Got 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. 

[Samogon]

It was repaired successfully. Will write short story later 

[giosif]

kkkkkkk, I think how did you came to the conclusion of the faulty CPU will be interesting in the repair forum.

Well, 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.

[giosif]

It was repaired successfully. Will write short story later 

Oh shoot!
Err... I mean "Well done!" 

[Samogon]

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 low
All 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.

[giosif]

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 low
All 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.

Cool! 
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.

[Samogon]

Well total spend approximately 3-4 hours over few days.

[giosif]

Well total spend approximately 3-4 hours over few days.

Ah, ok, so not exactly "instant fix", then.

[brokenslinky]

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.

Thanks 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.