Looking for Mettler Scale ROM backup  - Page 1
Forum section: electronics / repair

author: gmac34
author_rank: Regular Contributor
timestamp: December 17, 2023, 05:17:41 pm
content: Hi, I have a Mettler scale with a bad ROM, I tried to contact Mettler to see if they would share the 30y old ROM file with me but did not get an answer.If anyone has a copy, I think I need the "STANDARD SOFTWARE ME-34172" any version between 10.45 and 10.50 should work fine regardless of the model of the scale, this should be compatible with all scales from the era with the same cartridge ROM system.Attached a picture of the cartridge, inside there is just a regular UVPROMThanks!

author: fzabkar
author_rank: Super Contributor
timestamp: December 17, 2023, 05:44:04 pm
content: Can you upload a ROM dump? Or perhaps several ROM dumps? Perhaps it would be possible to perform a bitwise AND against all your dumps to create a hybrid ROM, assuming that errors are intermittent.

author: jamarjan
author_rank: Contributor
timestamp: October 16, 2024, 09:43:58 am
content: Hi gmac34attached dump of the ROM from my cassetteME-34172 STANDARD V10.32I hope it will help you fix your scale.I myself am struggling with a PM4600 scale that is not working.Probably as a result of dead low voltage dc capacitors, my NMC9346N chip zeroed out.According to the service manual of the scale, you need to program it with a special cassette and an external keypad.What is the model of your scale?

author: gmac34
author_rank: Regular Contributor
timestamp: October 16, 2024, 12:16:20 pm
content: hi jamarjan, thanks for the dump, I actually managed to get a newer version dumped as well, buying another scale...I attached them here as well for posterity.Regarding your problem, I believe you will have to contact a Mettler service center, try a few and see if one offers a reasonable price for the operation, I haven't manage to find copies of the service cassettes, but without those you will not be able to frost initialise the memory and tell the scale what it is but also input all the parameters for linearity and temperature compensation specific to your cell. I think they are written down in the real plate that you can remove to do the corner load adjustment.I also have pm4600, so maybe I could dump that memory, but my linearity and temperature compensation data will not be correct for your scale.I think I should dump that for posterity to keep my scale running, but that ic is not on a socket I'm a bit afraid of trying to get it off...

author: jamarjan
author_rank: Contributor
timestamp: October 16, 2024, 12:37:13 pm
content: Wow wow wow! What incredibly fascinating news!Thank you for your response.Desoldering the 8 pin ic is a relatively simple matter.A tin extractor and a braid allowed me to desolder in a few minutes.Later you can insert a 8 pin socket.Would be very grateful to you if you decide to rip this ROM.According to the service manual, the basic programming of the scale type just involves specifying the model and measurement range.Calibration of the parameters you write about is a completely different matter and you need yet another cartridge and procedure.The scale I am repairing is rescued from being scrapped and is actually for learning purposes.Well, and that beautiful VFD (in my case it works like new)!Also, once again, I would VERY much appreciate it if you would rip copy this internal IC at your leisure.I am absolutely not in a hurry. It can be in a week or a month.Thanks in advance!attached a dump of my IC- blank except for the first 2 lines

author: jamarjan
author_rank: Contributor
timestamp: October 16, 2024, 12:38:05 pm
content: and by the way if you haven't done it yet - replace the electrolytic capacitors in the power supply

author: gmac34
author_rank: Regular Contributor
timestamp: October 16, 2024, 01:31:58 pm
content: ok, here are the copies, I wasn't much afraid of removing them, I have a proper rework station for that, but rather heat and EEPROM do not go well togetheranyway here you can find the backup from my PM4600 and from my PM3000I think you could try to modify the rom to include the parameters from your scale, they should be saved inside the rom, attached you can see also the parameters from my scale, maybe you can find those numbers in the room and replace them with yours:"The measuring cell parameters, balance/scale type, linearization and temperature compensation are contained in 21 5-7 digit numbers. These numbers are printed on the parameter sticker on the inside of the cover plate."Let me know how it goes

author: fzabkar
author_rank: Super Contributor
timestamp: October 16, 2024, 06:15:23 pm
content: PM4600 dump:Code:Offset(h) 00 02 04 06 08 0A 0C 0E00000000 02D9 C013 4650 FF00 DA00 1302 2000 458700000010 3143 1902 2941 090A 3100 3102 0A02 00A000000020 BC00 0031 6480 0201 0202 0002 F400 1B4800000030 B542 0C16 3800 0000 0000 0000 0000 AEBA00000040 0780 343C 04BA 1189 E505 056E F9BA 6AFF00000050 FFEE 0258 7D00 FF1C 68C2 47FD 000C 0BBB00000060 8B00 0005 E115 86FF 0766 0000 8843 C0E800000070 1400 DE28 BC1C 0004 0000 0000 0000 0000These appear to be the 21 calibration parameters:Code:Offset(h) 00 02 04 06 08 0A 0C 0E00000030 AEBA00000040 0780 343C 04BA 1189 E505 056E F9BA 6AFF00000050 FFEE 0258 7D00 FF1C 68C2 47FD 000C 0BBB00000060 8B00 0005 E115 86FFCode:00: 306874 = 0x4AEBA - first parameter...20: 886527 = 0xD86FF - last parameterIt appears that the leading nibble is discardedThat is, 0x4AEBA is stored as 0xAEBA, and 0xD86FF is stored as 0x86FF.Product ID = 874543.Code:Offset(h) 00 02 04 06 08 0A 0C 0E00000000 458700000010 3143Model name = PM4600Code:Offset(h) 00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F00000000 46Model name = PM3000Code:Offset(h) 00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F00000000 30

author: fzabkar
author_rank: Super Contributor
timestamp: October 16, 2024, 07:41:46 pm
content: All the 32KB firmware dumps have an 8-bit checksum of 0x00. I don't know where the checksum byte is located, though.

author: gmac34
author_rank: Regular Contributor
timestamp: October 16, 2024, 08:03:41 pm
content: thanks for you effort, fiddling with binaries is a bit above my pay grade. If it is of any help I have also dumped the EEPROM of a PM200 and attached parameters for all 3

author: fzabkar
author_rank: Super Contributor
timestamp: October 16, 2024, 09:06:43 pm
content: 21 calibration parametersCode:Offset(h) 00 02 04 06 08 0A 0C 0E00000030 AEBA00000040 0780 733C 04AE 02FF 3F05 055D FBA9 8EFF00000050 FFF3 021A DC00 FF14 3C3E D6FD 000C F74B00000060 CEFF 0000 072C 9A00Product IDCode:Offset(h) 00 02 04 06 08 0A 0C 0E00000000 436900000010 1937Model number PM200Code:Offset(h) 00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F00000000 20

author: jamarjan
author_rank: Contributor
timestamp: October 17, 2024, 06:52:40 am
content: Thanks for the response!Unfortunately, it looks like my ROM wasn't damaged (it looks similar to yours).After the swap, the scale still won't start.For some reason, the microcontroller doesn't read the ROM's contents.I have some activity on the NMC9346N read pin, but from what I can see on the oscilloscope, the instruction (read) doesn't seem to be correct.All the voltages given in the service manual are within spec.The microcontroller is warm but not hot.The waveform on pin 1 uC doesn't appear every time the scale is started, and when it does, it has a strange waveform. I also have a not-so-nice XTAL2 waveform.I'm running out of ideas on what else to check.gmac34 I see that you know these scales quite well.I, on the other hand, am an amateur hobbist with a very limited amount of electronic knowledge.Maybe you have some tips for me?Either way, you have a big beer from me ;-)

author: gmac34
author_rank: Regular Contributor
timestamp: October 17, 2024, 07:01:58 am
content: Well, it seems your scale is not starting at all, in fact I think the scale is supposed to do some self checks at power up, and should give you an error in case the EEPROM is bad. As a first step I would suggest you try to burn the UVPROM with the 10.45 version above and make sure your is not corrupted. Do you have an UV eraser? a bad Cristal could also be a suspect.

author: gmac34
author_rank: Regular Contributor
timestamp: October 17, 2024, 07:05:15 am
content: BTW, this was the behaviour of the scale I was trying to repair at the beginning of the tread, the UVPROM was corrupted, just a few stuck bitsI think we can safely assume the problem is in the digital section so either microcontroller, UVPROM, RAM or Cristal, I don't think IC1 can stop the thing startingif you probed the Cristal correctly the waveform looks a bit wonky, so that could be easily replaced, next I would try the ram. I also assume that the analog part is working fine, do you see the beam move when you connect power? that part would work all the time, regardless of the state of the digital side

author: fzabkar
author_rank: Super Contributor
timestamp: October 17, 2024, 07:32:15 am
content: Can you upload the service manual or provide a link to it?

author: gmac34
author_rank: Regular Contributor
timestamp: October 17, 2024, 07:36:29 am
content: Not a very useful SM

author: fzabkar
author_rank: Super Contributor
timestamp: October 17, 2024, 08:04:19 am
content: I would check the data and address buses and the micro's reset pin.Just out of curiosity, I notice that U4 (ME47820P) and U11/U13 (ME84202) appear to be Mettler custom parts. U4 has a crystal, so I'm wondering what it does.

author: fzabkar
author_rank: Super Contributor
timestamp: October 17, 2024, 08:24:45 am
content: #jamarjan, your EEPROM is a 9346 (128 bytes), yet your dump is a 9306 (32 bytes). Why is that?

author: gmac34
author_rank: Regular Contributor
timestamp: October 17, 2024, 08:26:23 am
content: The other Cristal should be for the integrating ADC, ME47820P should be part of it, but not a integrated ADC ic, you see nearby a LM 393 comparator, Mettler unfortunately used a lot of parts with custom codes, but non necessary custom parts.given the position of U11 I would imagine it si just a precision op amps supporting the voltage reference, U13 is on the signal path coming from the measuring resistor, I know it can be replaced with a daughter board to adjust linearity, and that is all in the analog domain before the ADC.

author: gmac34
author_rank: Regular Contributor
timestamp: October 17, 2024, 08:33:49 am
content: this is a service manual for a Sartorius scale of the same era, I believe they are quite similar in their implementation, of the analog PID on one side the ADC in the middle and the microcontroller on the other.unfortunately this is the only schematics I have for this type of scales.IC106 in this schematics should be the counterpart of U4, it's a gate array, and has it's own oscillator

author: gmac34
author_rank: Regular Contributor
timestamp: October 17, 2024, 08:46:58 am
content: in the same guide about removing IC 13 they mention its is a LM358, Dual, 30-V, 700-kHz operational amplifiersee page 122

author: jamarjan
author_rank: Contributor
timestamp: October 17, 2024, 09:36:48 am
content: oh boy, what a fruitful thread it has becomeI need to calmly read and understand your posts ;-)fzabkar - of course I messed up with the rom dump - I mistakenly chose the wrong chip (I will delete my above post to avoid confusion)gmac34 - I use a mercury lamp to erase the uv epromunfortunately my chip after zeroing is not programmable, although I tried different combinations of voltages and delay times (I checked datasheet for my chip - fujitsu)i ordered some 27c256 chips both fujitsu and tii will report on progress

author: gmac34
author_rank: Regular Contributor
timestamp: October 17, 2024, 09:38:49 am
content: Then there is a good chance that a freshly flashed UVPROM is all you need

author: fzabkar
author_rank: Super Contributor
timestamp: October 17, 2024, 10:17:01 am
content: Quote from: gmac34 on October 17, 2024, 09:38:49 amIts checksum was 0x00, so it looks good to me.BTW, I use HxD (freeware hex editor).https://mh-nexus.de/en/hxd/

author: gmac34
author_rank: Regular Contributor
timestamp: October 17, 2024, 10:25:30 am
content: Right, I thought you checked the EEPROMs, in that case maybe the UV one was good, but it’s odd that it doesn’t program. Doesn’t it program at all or do you just get some write here and there?If it was my scale I would order a ram ic, I see it’s 3-4€ on eBay and if not a odd frequency the oscillator.

author: jamarjan
author_rank: Contributor
timestamp: October 17, 2024, 11:24:17 am
content: I swapped the crystal oscillator - the waveforms didn't changethe oscillator waveform itself doesn't look very bad, but the clock waveform from uC is not rectangularon the other hand, both ADC oscillator waveforms are perfectMy integrated circuit doesn't program at all - it can be read (it's filled with blanks), but it can't be programmedgmac34 I also ordered RAM d446c - they'll be here tomorrow

author: dustooff
author_rank: Contributor
timestamp: October 17, 2024, 01:29:46 pm
content: Hi,with regards to the MCU oscillator, I usually scope the ALE and PSEN pins to see if the MCU is trying to access any of the external memory devices, ALE should be1/8of the XTAL frequency, see timing waveform on page 25.If these external memory timing pins are active then the main XTAL clock should be fine.Then probe each data pin and address pin to check for less than optimal logic levels, sometimes a addr/data line can be stuck.regardsAndrewEdit: correction ALE is 1/6 of CLK frequency.

author: jamarjan
author_rank: Contributor
timestamp: October 17, 2024, 05:46:28 pm
content: fzabkar analyzing what you wrote I made a list of my parameters and dumped romI'm trying to recreate the configuration of my deleted romI have problems with positions 10 and 11can you tell me how to write it correctlyit's a bit strange that the first digit is omittedI'll stare at this ROM dump for a whilejamarjangamc34Model namePM4600hexmod_hexPM4600hex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

author: fzabkar
author_rank: Super Contributor
timestamp: October 17, 2024, 06:22:48 pm
content: Code:10: 59 0003B 003B11: 27136 06A00 6A00There is a typo here:886257 D85F1 85F1886527 D86FF 86FF <- this is correct

author: jamarjan
author_rank: Contributor
timestamp: October 18, 2024, 10:26:08 am
content: Hi Andrew and others.Flashed and reinstalled new EPROM - no changes :'( Still waiting for RAM chip.On ALE i have a nice square wave of 1,23 MHzOn PSEN similar with a little bit of noise on a high state.XTAL is about 7,3 MHzIn most cases I have no activity on pins of channel 1 (P1.X) where communication with ROM should be.Once every few restarts there is activity with waveforms not resembling those I found in the ROM datasheet (in / out).screenshots attachedThese waveforms appear once in a while (every 5th time the scale is used), usually there is no activity or it occurs very shortly after the scale is turned on - I am not able to record it on the oscilloscope.

author: gmac34
author_rank: Regular Contributor
timestamp: October 18, 2024, 10:45:38 am
content: Did you check continuity between the uvprom and the board? Check that all data line are going trough the connector, also check for corrosion or bent pins.

author: dustooff
author_rank: Contributor
timestamp: October 19, 2024, 10:21:15 am
content: Quote from: jamarjan on October 18, 2024, 10:26:08 amIs port 1 actually connected to the ROM/RAM devices?My understanding of the data sheet says...Port 0 is also the multiplexed low-order address and data bus during accesses to external program anddata memory.andPort 2 emits the high-order address byte during fetches from external program memory and duringaccesses to external data memory that use 16-bit addresses.In the past I have repaired two PM4600's one for VFD problems, the other was failing to startup, like your current situation, unfortunately I can't recall the specifics of how the repair went. And I currently own it.Edit: found app note AN457 (but not on NXP's site) look at Figure 20, the 74HC373 has to hold the low address while the MCU presents the data byte.Check the 373 output for an address, may need a LA to do that.

author: jamarjan
author_rank: Contributor
timestamp: October 26, 2024, 05:15:32 pm
content: I've had a brief break in fixing the scale due to a business trip.I replaced the UPD446C CMOS SRAM, 74HC373 chip, uC P8031, and the resistor ladder (it looked like it had a crack).Still no change.The clock waveform is still not square.On startup there seems to be some activity on the uC communication with the ROM.However, it seems to me that it does not load the program.I guess I actually need to equip myself with a logic analyzer and take a look at the uC - ROM communication.

author: gmac34
author_rank: Regular Contributor
timestamp: October 27, 2024, 05:16:12 am
content: Sorry to hear that the part’s cannon approach didn’t lead to anything.In a few days I will be back home, if you need I can probe around on mine and compare things.

author: jamarjan
author_rank: Contributor
timestamp: October 29, 2024, 09:50:47 am
content: I managed to play around with a logic analyzerI am posting screens from channel P0, P1 and from the EPROMit seems to me that the microcontroller is not reading data from the epromjust why it is not displaying any error on the VFDgmac34 - can you check how your scale behaves when you unplug the connector ( blue) from the weighing module? and how about when you unplug the interconnect board with the rear connectors?

author: gmac34
author_rank: Regular Contributor
timestamp: October 30, 2024, 08:11:47 am
content: nothing happens if I remove the communication board, I think it was an optional anyway, and I get error 4 ( Error in temperature measurement) with the cell disconnected.

author: jamarjan
author_rank: Contributor
timestamp: October 30, 2024, 11:33:42 am
content: Thanks for checking and the information providedUnfortunately my efforts are still without progressI also checked the proper operation of the optotransistor controlled by the integrated switchEverything seems to work okWhen switched on the scale consumes about 9W of powerUnder thermal imaging nothing heats up above the expected levelI'm trying to analyze what could have gone wrong due to badly filtered / unstable power supply voltage but without a schematic my skills are already exhaustedI guess I have to hunt for a twin used scale

author: dustooff
author_rank: Contributor
timestamp: October 30, 2024, 12:58:22 pm
content: maybe there are some mainboards available somewhere,https://www.ebay.com/itm/134203907609

author: gmac34
author_rank: Regular Contributor
timestamp: October 30, 2024, 01:32:18 pm
content: Is there any activity on pin 9 of the microcontroller (reset)?

author: gmac34
author_rank: Regular Contributor
timestamp: October 30, 2024, 01:46:55 pm
content: Non having a schematics is bummer, but one last thing that comes to mind is to check the IC1, the PC74HC373P. but I don't fully understand what is it doing there, by the position it would seem like it would interface between the ROM and the micro.

author: PA0PBZ
author_rank: Super Contributor
timestamp: October 30, 2024, 03:32:22 pm
content: Quote from: gmac34 on October 30, 2024, 01:46:55 pmThe lower 8 address lines and the data lines are on the same processor pins, so they need to be 'demultiplexed' and latched. See reply #31 in this thread.

author: jamarjan
author_rank: Contributor
timestamp: November 05, 2024, 01:12:01 pm
content: I connected the logic analyzer to the 373 latchbelow is a screenshot with the channel descriptionsunfortunately I don't really know how to interpret it

author: gmac34
author_rank: Regular Contributor
timestamp: November 05, 2024, 02:51:53 pm
content: I cannot help you with that, but I have one last thing I think you should check: I would check the data input on the vfd controllers, should be pin 39, to see if they are receiving any data. A bad controller might be another explanation for a blank screenhttps://www.digchip.com/datasheets/parts/datasheet/477/SN75518N-pdf.php

author: jamarjan
author_rank: Contributor
timestamp: November 06, 2024, 06:49:41 am
content: Thanks for the suggestions!Actually, the diagnosis after repairing the power supply and restoring stable voltages at the control points I just started with the VFD controllersUnfortunately there is no data reaching the display board (voltages are ok)The only life I get on the display board is if I run the scale without the cassette. Then all segments light up. I can turn the display off and on by pressing the spacebar button.It seems to me that driving the display is secondary to loading data from the EEPROM. And here, unfortunately, I have no information exchange between the uC and the memory.

author: gmac34
author_rank: Regular Contributor
timestamp: November 06, 2024, 07:26:25 am
content: I see, well, for what is worth the display lighting up with no cassette is normal behaviour

author: gmac34
author_rank: Regular Contributor
timestamp: November 12, 2024, 09:10:42 am
content: there is a "for now" cheap scale on eBay that could be a good parts donorgiven the state of the vfd I would imagine the cell to also be mechanically damaged but the main board may be okhttps://www.ebay.it/itm/335651376850

author: jamarjan
author_rank: Contributor
timestamp: November 12, 2024, 10:08:20 am
content: Thanks. The current bidder is me ;-)

author: gmac34
author_rank: Regular Contributor
timestamp: November 12, 2024, 12:07:05 pm
content: Good luck then.In the meantime I was trying to figure out which values in the EEPROM might be those of the linearity adjustment as my PM3000 is a bit out of specifications, it's a challenge to figure out what is what.The most confusing part is what happens to the parameters when they get written in memory, for example the first parameter for all 3 of my scales is written as AEBA even tough it is three different numbers written on the various parameter sheets. 3 different numbers that wen converted to hexadecimal end in AEBA but I cannot understand what the first part might be there for

author: gmac34
author_rank: Regular Contributor
timestamp: November 13, 2024, 08:45:21 am
content: Well, it seems you got it. the main board has the same part number between the pm6000 and 4800 hopefully you will just have to move over the reference resistors R41 and R42, and the memory

author: jamarjan
author_rank: Contributor
timestamp: November 14, 2024, 11:49:38 am
content: Yes, I bought the scale and it's on its way to me nowI can tell from the pictures that the scale has been mistreated so I don't have high expectationsI will let you know when I install the circuit board, and ill also try to dump the memory to have another bin for analysis ;-)

author: jamarjan
author_rank: Contributor
timestamp: November 21, 2024, 09:06:16 am
content: Weight arrived.After motherboard swap, re-soldering the reference resistors and reprograming momeorymy scale works perfectly.I calibrated it with 1000g standard.It is very accurate and the measurements are repeatable.For future reference I am uploading a memory dump and a photo of the nameplate for the PM6000 scale.I feel unsatisfied with the scale repair attempt, but on the other hand I learned a lot thanks to everyone who wanted to contribute in this thread.THANKS!

author: gmac34
author_rank: Regular Contributor
timestamp: November 21, 2024, 12:13:42 pm
content: Well, to be fair, in the end you have done exactly what the service manual tell you too do in these situationsCould you tell what you needed to do to get the scale programmed, I imagine you started with my copy of the EEPROM, did you just replaced the numbers with those from your scale?Attached you can find a nice document that tells you how to check a balance, if you want to be sure it's performing within specifications.Enjoy your Mettler

author: gmac34
author_rank: Regular Contributor
timestamp: January 21, 2025, 09:47:11 am
content: I have given up on modifing direclty the EEPROM variables so to fix linearity on one of my scales I resorted to a different approachhttps://www.eevblog.com/forum/repair/mettler-pm-pj-linearity-board