Replacing SRAM/FROM Fanuc 21i

pgmrmike · Oct 14, 2019

I have been having issues with a Fanuc 21iTB. According to the book the symptoms show a hardware issue, and replace either main board or SRAM. We replaced the main board but it didnt fix the issue. I contacted Fanuc to get a SRAM and they are saying a Fanuc tech has to do it because its a FROM/SRAM card and there is data that has to be loaded that I cant do.

What other data is ther besides ladder, parameters etc? We did the hold 2 buttons at startup and back up all the info procedure. It seems like we could replace card and start boot and load it all back? What am I missing?

Vancbiker · Oct 14, 2019

AFAIK, if you have successfully backed up all the FROM and SRAM (options 4 and 5 on the boot maintenance screen) that is all the control data including your CNC software. FROM has CNC software, builder ladder and any other builder stuff like custom U/I or functions. SRAM has CNC and PMC parameters, programs, pitch comps, offsets, etc.

I'm guessing Fanuc has had folks buy the part and eff up the backup/restore process leading them to just say their guy has to do the job.

pgmrmike · Oct 14, 2019

Vancbiker said:
AFAIK, if you have successfully backed up all the FROM and SRAM (options 4 and 5 on the boot maintenance screen) that is all the control data including your CNC software. FROM has CNC software, builder ladder and any other builder stuff like custom U/I or functions. SRAM has CNC and PMC parameters, programs, pitch comps, offsets, etc.

I'm guessing Fanuc has had folks buy the part and eff up the backup/restore process leading them to just say their guy has to do the job.

Exactly what I was thinking. The saved backup is 21 files. Names include ncbasic, minfo, pmc-sb, sram, cncparam, graphic, nc1_optn etc.

pgmrmike · Oct 14, 2019

Will the boot screen come up with the new card in so I can attempt to load it? I can get another card and try it, if I can still access the boot screen on start up. What worries me is that one of the issues I am having is that the control stops and shows sfail on start up. When I hold the keys to start in boot screen, it still shows sfail and wont turn on, I was thinking that starting in boot screen caused it to start without accessing sram so you reload sram etc. Doesnt make sense. Thats one reason I suspected main board in the first place...

Rick Finsta · Oct 14, 2019

Can you reload it with the 7-segment LED and rotary switch/pushbutton directly in the control cabinet? I just had to learn to do that today on my 0i LOL...

Vancbiker · Oct 14, 2019

pgmrmike said:
Will the boot screen come up with the new card in so I can attempt to load it? I can get another card and try it, if I can still access the boot screen on start up. What worries me is that one of the issues I am having is that the control stops and shows sfail on start up. When I hold the keys to start in boot screen, it still shows sfail and wont turn on, I was thinking that starting in boot screen caused it to start without accessing sram so you reload sram etc. Doesnt make sense. Thats one reason I suspected main board in the first place...

I've not seen this, but it sounds deeper than a failed FROM or SRAM module. There must be a boot load firmware that runs when the control is started normally or in maintenance mode. I'm guessing, but the sfail error sounds like the boot load is not running properly.

pgmrmike · Oct 14, 2019

Vancbiker said:
I've not seen this, but it sounds deeper than a failed FROM or SRAM module. There must be a boot load firmware that runs when the control is started normally or in maintenance mode. I'm guessing, but the sfail error sounds like the boot load is not running properly.

Im assuming this issue is related to other issues I am having/have had. All started with freezing on "graphics is ready" on startup. Then 935 ecc errors when on. Reloading sram would fix the 935 alarm. Then started this sfail on startup. The book shows its a sram or main board issue from what I can tell. But I dont actually know anything. It will eventually come on, though sometimes take 8 plus tries. Boards show 5.02 volts or so.

Vancbiker · Oct 14, 2019

pgmrmike said:
......It will eventually come on, though sometimes take 8 plus tries. Boards show 5.02 volts or so.

Ahhhh...., that multiple attempts and finally will run may be a clue. Have you put an oscilloscope on the power? I've seen failing power supplies show a decent voltage but have too much noise or ripple in the power and cause weird trouble. Voltmeter won't show or catch it, but an o'scope will.

pgmrmike · Oct 14, 2019

Vancbiker said:
Ahhhh...., that multiple attempts and finally will run may be a clue. Have you put an oscilloscope on the power? I've seen failing power supplies show a decent voltage but have too much noise or ripple in the power and cause weird trouble. Voltmeter won't show or catch it, but an o'scope will.

No. That is beyond my knowledge unfortunately

Rick Finsta · Oct 14, 2019

If you've got a laptop with a 3.5mm microphone input you can actually solder together a quick protective circuit using a few cents worth of diodes and use free oscilloscope software instead of buying one. Most of the cheap scopes are limited (my toolbox unit only goes to 10V, for instance) in their use. Once you've used a scope to diagnose electronics you'll wonder how you did it without one.

This schematic is courtesy of James Cortina:

pgmrmike · Oct 15, 2019

I am starting to wonder......Fanuc is saying the original card A20B-3900-0163 is no longer available. The replacement is A20B-3900-0283. I cant help but wonder if the new one is "protected" like the newer controls ( I have read that system files are protected now and only Fanuc has the ability to issue the certificate to make it work ). Maybe the old card is not protected the same way. I dont see how the original is no longer available when there are so many out there and they refurb and sell used boards/cards.

Vancbiker · Oct 15, 2019

That thought never occurred to me. It is possible that new boards/boot firmware could have some kind of password or even hardware "protection".

One thing I did see from the manual is that the FROM and SRAM and DRAM are on separate boards, not combined on one.

pgmrmike · Oct 16, 2019

Vancbiker said:
That thought never occurred to me. It is possible that new boards/boot firmware could have some kind of password or even hardware "protection".

One thing I did see from the manual is that the FROM and SRAM and DRAM are on separate boards, not combined on one.

Fanuc World has one of the original cards. I contacted their support and they think the "new card being protected but not the old one" theory is plausible, but wouldnt/couldnt say for sure. They had me check some parameters and files and it appears to not be protected. They are being very helpful and really seem to want to help get this fixed. We discussed it a bit and I decided it was worth a try to buy it and try it. The card itself would cost less than just the traval time for Fanuc to come out here, much less the repair time.

Of course it still may be necessary....if this doesnt work I will buy a o-scope and try to figure that out.

Not sure about location of sram/from and dram. Fanuc is saying from and sram are on this card. What that means for startup etc, I dont know

Vancbiker · Oct 16, 2019

pgmrmike said:
.......Not sure about location of sram/from and dram. Fanuc is saying from and sram are on this card. What that means for startup etc, I dont know

My 21i manuals are for an A model. You must have a B or later because the board part number you posted is not listed in my book. I did look at some 21iB info I have and it did mention FROM and SRAM on one board but that p/n did not match what you posted either. Needless to say Fanuc and Fanuc World (TIE) have way more info available than I have.

pgmrmike · Oct 18, 2019

Vancbiker said:
My 21i manuals are for an A model. You must have a B or later because the board part number you posted is not listed in my book. I did look at some 21iB info I have and it did mention FROM and SRAM on one board but that p/n did not match what you posted either. Needless to say Fanuc and Fanuc World (TIE) have way more info available than I have.

Yes, it is a B. The card came in today and I put it in and it allowed me to load all the system files. It appears as if Fanuc did replace the original part number with one that locks us out. Seems pretty crappy to do that to people running a 15 year old machine..anyway, machine came right up. Had to p cancel to find home but all was normal.

Turned it off and on and danged if it still hangs at start up. Still lights sfail. Dont know if any of the other issues are solved. I have replaced both boards the fanuc book says could be the issue so I guess its time to check out the power supply...

pgmrmike · Oct 18, 2019

Vancbiker said:
Ahhhh...., that multiple attempts and finally will run may be a clue. Have you put an oscilloscope on the power? I've seen failing power supplies show a decent voltage but have too much noise or ripple in the power and cause weird trouble. Voltmeter won't show or catch it, but an o'scope will.

Are you talking about the big one in the back control cabinet or the little one on the main board? It appears the small one on the main board knocks it down to 24 and 5v?

Vancbiker · Oct 18, 2019

I would scope all the power supplies. Some Fanuc models power the control from an external 24V supply and the internal module is a DC-DC conversion circuit to create the other voltages needed. Other models power the control with 200VAC and have a dedicated switching power supply for the needed voltages. I believe both types might have been available in the 21iB series. I know both types were available on the 21iA series.

memoryman · Oct 24, 2019

afaik, the -028X modules are a direct replacement for the -016X ones. There is no 'lockout' on either type. Both have flash and sram on the it, dram is on a different module. On startup, the system software is transferred from flash to dram and executed from there. There is an secondary method for entering the BOOT mode, that allows system software saving/loading; the normal method does not.
Starting in 2005, Fanuc 'locked out' option activation by just turning on the appropriate bits; if on the label (back of cage on LCD) has OP after the control ordering #, it is the newer type with options locked out.
At present you need Fanuc to help you with that.

pgmrmike · Oct 25, 2019

memoryman said:
afaik, the -028X modules are a direct replacement for the -016X ones. There is no 'lockout' on either type. Both have flash and sram on the it, dram is on a different module. On startup, the system software is transferred from flash to dram and executed from there. There is an secondary method for entering the BOOT mode, that allows system software saving/loading; the normal method does not.
Starting in 2005, Fanuc 'locked out' option activation by just turning on the appropriate bits; if on the label (back of cage on LCD) has OP after the control ordering #, it is the newer type with options locked out.
At present you need Fanuc to help you with that.

I reloaded all data from the special key startup mode ( dont know what its called, but not the 2 soft keys next to each other . Are you saying the way the startup process works, if it hangs on startup and shows sfail, it could be dram module? I havent checked power supply yet with oscope.

Leadnuts · Jul 19, 2021

did you ever find the solution to your problem? I have a similar one on a T14iaL.

Replacing SRAM/FROM Fanuc 21i

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