Can anybody help?
We came across fault codes FC432 to FC436 "Logic Signal $256L Voting Mismatch," but could not find any document related to it. From GE 6421 manual we found only fault codes up to #415. The FCs appear on slot9 VCRC together with TRLY J4 fuse 01 (to 06) blown and Coils 05, 01, 03 & 07.
When did this problem start?
After a trip?
After some kind of loss of 125 VDC?
After a 125 VDC Battery Ground?
After a download from Toolbox?
After a VCRC card was changed?
It's unusual for a Mark VI to annunciate Diagnostic Alarms that are "outside" the window for drop numbers (Fault Codes), but it does happen. In my experience, it usually happens after one or more of the above scenarios happens--and usually after a card is replaced and one or more downloads have been done.
Additionally, what OTHER Diagnostic Alarms are being annunciated by the VCRC?
Is the VCRC a SIMPLEX VCRC, or a TMR VCRC? (In other words, if the VCRC is in slot 15, for example, of <S>, for example, are there also VCRC cards in slots 15 of <R> and <T>, or not? (If there were also VCRC cards in slots 15 of <R> and <T>, then it would be a TMR card. If there were no VCRC cards in slots 15 of <R> and <T> then it would be SIMPLEX card. And, this is all presuming the panel is a TMR Mark VI; if it's not, can you please tell us?)
A voting mismatch indicates that the current value of a signal in one or more processors does not match the current value the same signal in the other processor(s). Sometimes (most often) this occurs because of problem with the card the signal "originates" on, but sometimes, as with outputs (and a TRLY card is a discrete output card) it has to do with a problem with the aux contacts of the relay(s) in question not producing the proper indications (the relay is supposed to be picked up (energized), and the relay aux contacts should be indicating the relay is picked up but they aren't, or vice versa (the contacts are indicating the relay is picked up when it is not supposed to be picked up).
I have also seen similar problems caused by people connecting the 37-pin D-sub cables with power on the circuits. It's VERY EASY for the pins of the male connector to be shorted against the shroud of the female end of the connector when trying plug in the cable when power wasn't properly removed. This can occur at BOTH ends of the cable (in this case, the cables that connect the VCRC card to the TRLY card). the sparks generated when this happens may or may not be visible, so the person trying to re-connect the cables may or may not have seen them to know of the problem. But, it can cause problems with both the I/O card (the one in the processor rack, the VCRC in this case) and/or the I/O terminal board (the TRLY in this case).
You also mentioned problems with fuses.... Are the relays you mentioned actually assigned (used) in the application, or are they spares (unassigned)?
LOTS of questions, I know--but most of them are intended to prompt some thought and investigation. Yes; it would be very helpful if you would provide the answer to ALL the questions (even if they don't seem relevant), but please do provide write back on what you find as you resolve the issue!
Hope this helps!!!
Thanks for the reply. We are still actually puzzled with the event that is why we are analyzing it (internally). The GT was re-started successfully but we are not confident that it would not happen.
>When did this problem start?
The alarms came before the TRIP initiated by
>After some kind of loss of 125 VDC?
There are no evidence of any loss on any of the redundant power supply? Besides there is no recorded power dip or loss in any of the cards or from PDM module.
>After a 125 VDC Battery Ground?
There is no evidence of any ground fault.
>After a download from Toolbox?
I'm not familiar with the "toolbox" but the alarms are DALMLOG provided by GE services
>After a VCRC card was changed?
There are no recent card replacement.
>Additionally, what OTHER Diagnostic Alarms are being
>annunciated by the VCRC?
I can provide you with the list of alarms.
>Is the VCRC a SIMPLEX VCRC, or a TMR VCRC?
We have TMR VCRC.
>You also mentioned problems with fuses.... Are the relays
>you mentioned actually assigned (used) in the application,
>or are they spares (unassigned)?
Fuse blown indication occurs on TRLY output cards with assigned and unassigned outputs. One of the load is solenoid each for Slot 9 and Slot12 output cards, provided with the respective jumper connection. Since there are no indication of actual voltage drop and the TRLY has a fuse blown monitoring to activate at <14V, is there any likelihood of card malfunction.