Agilent 34901 Mux card for 34970 DAQ unit. - Page 1
Forum section: electronics / repair

author: PTR_1275
author_rank: Frequent Contributor
timestamp: September 22, 2015, 09:31:07 am
content: Hi everyone,I bought a known non-working 34901 mix card for the 34970 data acquisition unit recently. I have plugged it into the 34970 and I am getting a 913 error. There is nothing listed in the manual that I have about this error, but googling it turns up that the "Module returned nonvolatile memory fault".Looking through the schematic, there is a FRAM on the board (U150) which is a 24C04-S. Is it a matter of just replacing this, being a FRAM, does it need to be programmed with anything, it says nonvolatile memory error which makes me think that it needs to be programmed, but RAM to me is not programmed before installation.I checked the board over for damage before plugging it into the 34970, so I was hoping that it was just some relays that were busted when I bought it. It still opens and closes the relays and takes readings, so I am not sure what the error is affecting. If anyone out there has any more insight with things I should check, please let me know.Cheers-Chris

author: 6thimage
author_rank: Regular Contributor
timestamp: September 22, 2015, 11:01:36 am
content: FRAM is non-volatile storage - it's like eeprom or flash, but can endure more write cycles (although reading counts as a write cycle, as it is destructive).The Agilent/Keysight DAC boards use them to store the number of times the relays have been switched, so it can be predicted when they will fail / need to be replaced. So by replacing the FRAM you will lose that information, although it sounds like it is already lost. I'd hope that the DAC unit would initialise the FRAM if it is blank, but you might have to write something to it yourself. I'd try throwing in a blank chip and if it doesn't work (or you get more error messages) contact Keysight.

author: HighVoltage
author_rank: Super Contributor
timestamp: September 22, 2015, 11:33:45 am
content: Most likely all data will be written to it after you replace it.So, it should be safe to just exchange the 24C04-S

author: PTR_1275
author_rank: Frequent Contributor
timestamp: September 22, 2015, 12:29:46 pm
content: Awesome, digikey order is in the works anyway so I'll grab a couple of spares.One of the relays had over 4 billion actuations so I will test the relays too and make sure they are all ok. The relays are $5 each from digikey and they aren't handling big currents so I wouldn't have thought the contacts would be damaged.There is a 34907 dac and totalizer card that has some damage, looks like the dac was overloaded and has burnt some tracks and some capacitors near the terminal block. That's the next job though (in a list of many)

author: TiN
author_rank: Super Contributor
timestamp: September 23, 2015, 04:06:33 am
content: If replacing I2C EEPROM would not help, I can dump a binary from working 34901A.

author: FFFF00
author_rank: Contributor
timestamp: September 23, 2015, 04:54:11 am
content: I have a 34902A card with the same error (913) where I replaced the FRAM using a FM24C04B-G. This unfortunately didn't resolve the problem for me.I can confirm that my 34970A starting counting relay cycles from 0 with the new part without other errors. There may be another area in memory that it reads that isn't normally written to. I don't have a good card (identical) to compare against.I also tried reseating the MCU in its socket which did nothing, although I didn't expect it to.

author: FFFF00
author_rank: Contributor
timestamp: October 16, 2016, 02:15:08 am
content: I wanted to follow up because I fixed error 913 on my 34902A card. I finally found another 34902A and copied the FRAM contents to a new part and installed this in my old card. No more 913 error.The service manual says that the thermocouple calibration is stored on the card, so swapping the FRAM contents will invalidate this calibration on the 34901/2/8A.I've included the contents from my card in case it helps anyone.

author: HighVoltage
author_rank: Super Contributor
timestamp: October 16, 2016, 08:43:42 am
content: Congratulations on your repair.I don't have a 902 card but stored your file away, just in case it will be needed later.Thanks