Home Forums General Discussion Technical Questions Miprom 21 "No BC Feedback" Fault

Working on a Miprom21 DDC that has "No BC Feedback" fault

I understand that this is a MSU "BCI" (Balance Complete Input) that originates from the drive "Motion adapter" board

with the ribbon cables it's difficult to meter this signal

I have re seated ribbon cables, boards, changed both "BCX" and "BC" relays with no luck

I'm leaning towards faulty "Motion Adapter" board in drive

Is there something else I should be looking at that this "BCI" input monitors that I can check?

Thanks for any suggestions

Auxillary M contacts?

Yep aux M contact or a bad relay, or a bad relay pilot bd. Check sheet 2 of the prints for the BCI and BCX circuits. You also need the drive ready light in the drive to be high.

And if M does pick, sheet 8, top of the page, you need to get enable input to the drive. I don’t remember if you need run too before the drive will pick BCX but you definitely need enable. And if M is not picking, don’t forget about the little PR pilot relay buried up in the drive.

Thxs for the info...

NC aux M contacts meter good but the M contact never pulls in to check NO aux contacts.

I was under the impression that because I have a DDC and not a anolog drive( uses aux M contacts) that my BC signal is originated from drive then routed back to MSU board through BCX and the MC contacts

I'm looking at some prints now...looks like I may have overlooked a BJ1 pilot relay that is right before BCX....and if I recall correctly I believe the job specific prints(500 FPM) at building shows my ETS circuits running through M aux contacts(which may explain why none of the ice cube relays are lit up but my high and lo voltages are good to board)

Rodger that...I will also look at PR pilot relay
Thank you Sir

Someone please correct me if I get this sequence wrong. MSU picks a direction relay, U or D, P contactor picks through N/C M contact etc. sheet 3. On sheet 8, ENA relay and LED on relay pilot board pick through direction relay and P, CO LED should also light. CO signal goes to drive on sheet 10, picks K2 drive relay, drive picke K3 relay. When K3 and K2 pick, PR contactor pilot relay should pick (H-5) which picks M contactor (D-12)

To correct my earlier post, you don’t get Run until M and then brake contractors pick. Also, the pilot relay isn’t always used. I think it depends on the size of the M contactor.

I don’t know what all is envolved with the drive picking K3 though, maybe someone else knows more about it.

I will continue troubleshooting tomorrow and follow up, thxs again

If P2 doesn’t drop out after a run, you’ll never get M. If these are the OEM (or I guess AB could flake out) relays (SB, SBD, P2 etc), no doubt time to renew them as that pneumatic timer craps out.

Thank you good info...as for most, Mondays are always crazy, didn't get to go by there today, been playin with composites all day

Miprom21...out of those3, P2 is the only one that does pull in, I haven't bothered metering the NO NC contacts on it as I've been focused on the "No BC Feed Back" fault and the related circuit....now you have me thinking it's one of the NO or NC P2 circuits, I will find out tomorrow and follow up

and yes they do look to be OEM with original timers

Be sure to check if you haven’t, each wire connection at those three relays. Broken wires, shorted caps at the coils (open fuse would be evident there) are common. Same on the “M” contactor coil and aux contacts...They can be broken right at the terminal screw (crush point), or fried inside the relay terminal point and your eye may not see it. Be sure your brake contact is functioning correctly.

Good luck

Is the m contactor like the one on a analog a&b drive? I've had those give me issues before logging 14 faults if I remember right. I replaced all the AUX contacts on m contactor even though they metered out fine. It turned out that that mechanism of the contactor that opens/closes the AUX contacts was worn out causing 14 faults.

yes sir I was getting VP 14 faults, I never once saw the M contactor pull in...the P2 was the only one pulling in but good info Thxs

With elev on 2nd landing I had a mis match with Red led NTSI input off and Green ETS output on...it was difficult to troubleshoot the ETS boards in bottom of controller with original ice cube relays, hard to tell if they were picked or not so I replaced them all along with the ETS and NTS ones on upper swing panel board with the user friendly IDEC ones with LED and the elevator took right off, observed operation for an hour with no issues.
Wish I could report what the smoking gun was and issue may vary well come back.

Someone did mount a ice cube relay that when pushed it pulled in M contactor(nice way to verify good coil)....didn't trace wires out so not sure what the purpose was

Hats off to the Gents with all the Miprom knowledge....those can be a real Bear!

That’s probably the Pilot relay. Once you dig it out from the drive it doesn’t feel like a great idea to replace it and bury it back in there. I add a base and a KUP relay rather than replace the old. Based on which relays you said you replaced and the fact that P2 was picking, I would bet on the P or NTS relay contacts on the relay interface board. Or a U or D contact if it was directional. But you didn’t notice if the ENA and CO LEDs on the Relay Pilot board were lighting?

Yeah they can be.
You mentioned replacing the Bottom and Top ETS/NTS speed relays in the box at the bottom of the controller;

Those are low current bifurcated relays, not your run of the mill IDECs. So, when you get a chance, assuming the ones you’ve used aren’t the low current type, replace them asap. IDEC makes them, I just can’t remember the p/n (4zyn-something er other?).
And no doubt that separate ice cube relay near the drive is PR as IDWT said.

Hopefully the unit continues to run for you (and your customer).

good info about the low current relays...can't remember part numbers. Someone before me had already replaced all ETS/NTS on other controller so that's where I got part#. I will definitely look into if they are the correct ones.
Those miproms for the most part are solid performers. In the MR I past by them controllers at least once or twice a week for a call on old 30UCL Serv Car...I knew the day would come when I'd have to jump in there and get some Miprom schooling...My old school stupervisor said ahh ya don't need that service tool, just go off the I/O Leds...as far as faults I think he's right..as far as prints some of the easiest to read.