Prisma elevator door controller, damaged psu, need identify components[SOLVED]

[Harry_22]

Zeners can be 13 volts. This is enough to start the controller (Vcc=9V max).
The main thing is that after start-up Vcc voltage rises slightly (up to 10-11 volts) and turns off Q32.

[timeandfrequency]

Buy also a replacement for R114 (100 k).
10 k seems pretty low (lead to a start current of  I = 31 mA)
If the controller does not start with 100 k, you can still try 10 k in a second attempt.

[Harry_22]

100k resistor will not burn out as much as 10k in case of Q32 short.

[timeandfrequency]

100k resistor will not burn out as much as 10k in case of Q32 short.

I already noticed your explanation above.
Let me just allow to have different opinion than yours.

[Poroit]

G'day All,

I am not sure if the attached is a help or a hinderance but it contains similar components to the damaged PSU.

I have seen similar damaged components in these as well.

I do not have a schematic.

[Harry_22]

G'day All,

I am not sure if the attached is a help or a hinderance but it contains similar components to the damaged PSU.

I have seen similar damaged components in these as well.

I do not have a schematic.

Hi Poroit!

Yes, yours PSU is mostly similar.
PFC provides its own Vcc supply. That is why low power start-up UCx845 is used there.
Also 50% duty cycle is usually used with the high power transformer.

[timeandfrequency]

Hello Poroit,

G'day All,

I am not sure if the attached is a help or a hinderance but it contains similar components to the damaged PSU.

I have seen similar damaged components in these as well.

I do not have a schematic.

Can you confirm that the document you provided shows an elevator door controller from Prisma ?

[timeandfrequency]

About Z14  (Vz = 11 V in the latest schematic)
@PiotrMisiuna Any marking on the zeners ?


Minimum PWM controller startup voltage depends on IC reference :
UC3842 &  UC3844 : 16 VDC   :  Z14 value is underrated, PWM controller will not start
UC3843  &  UC3845  : 8,4 VDC  : Z14  value is OK


Interesting sentence in chapter '7.3.5 Undervoltage Lockout' of the datasheet :

During normal circuit operation, VCC is developed from auxiliary winding NA with DBIAS
and CVCC. At start-up, however, CVCC must be charged to 16 V (*) through RSTART. With a start-up current of 1 mA,
RSTART can be as large as 100 kΩ and still charge CVCC when VAC = 90 V RMS (low line). Power dissipation in
RSTART is then be less than 350 mW even under high line (VAC= 130 V RMS) conditions.


(*) Actual minimal startup voltage depends on IC model, see above.

Reminder : as PiotrMisiuna is located in Europe, VAC = 240 V RMS @ 50Hz (hence DC rail voltage = 339 VDC)

[Poroit]

G'day timeandfrequency,

Unfortunately not.

It is an SMPS from a 25 year old Air Data Test Set.

[timeandfrequency]

Unfortunately not.
It is an SMPS from a 25 year old Air Data Test Set.

Thanks Poroit for this information.
These UCx84x switchers have numerous applications and were used in many different designs.
This thread is about the repair of a 'Prisma elevator door controller'.
Unfortunately, the board you showed can not really be used as reference to identify the fried parts we have on that elevator controller.

[PiotrMisiuna]

I believe the repair is successful. Powered up on the workbench effected in one of  LED lights going red and some relays going click.  Now I will pass it and wait for feedback from the elevator technician. 

[timeandfrequency]

That's good news.
Keep us updated.
If possible, post again the latest version of the schematics, with the actual parts values/references you used to repair the board.

[PiotrMisiuna]

Ok, controller installed. I didn't expect it to be placed in such idiotic place. Right above the door with all the connectors facing upwards. Wash the floor one level up and spill more water..... you know.  Elevator guy wasn't to happy, but we installed it, tested and it works as supposed to.  I found a manual in the shaft so I got it  scanned. I skipped introduction and table of contents. Attached.

schematic I followed is like in this response https://www.eevblog.com/forum/repair/prisma-elevator-door-controller-damaged-psu-need-identify-components/msg5739749/#msg5739749

[timeandfrequency]

Hello PiotrMisiuna,

Great to hear that the elevator door is now fully functionnal .
Thanks for the documentation.
You may now edit the title of this thread by adding the word that everyone wants to see in the repair section of the forum : '[SOLVED]'


The elevator guy wasn't too happy.
For him, it's of course easier to litter the defective assembly and install a brand new one, problem solved.
I would say that for sustainability reasons, we will probably need to make more 'component level' repairs in the future. With more and more boards that are fully populated with SMD parts, it's not an easy challenge. And without any schematic as for your elevator door board, it is even more demanding.


I didn't expect it to be placed in such idiotic place. Right above the door with all the connectors facing upwards. Wash the floor one level up and spill more water..... you know.
Well, at a certain level of nonsense, you can't exclude that the board was strategically installed at this location so that water spilling from the above floor just drops at the right place to fry the assembly . You mentionned in an earlier post that the cost of a replacement board was really high. No real need to look anyware else.

To avoid future hassle, consider protecting the electronic assembly with a plastic bag hold by some duct tape. Using a mylar/plastic sheet to build a small roof above the assembly might be another solution. Stick the plastic sheet with strong epoxy glue.

[PiotrMisiuna]

Elevator guy wasn't too happy because I got access to the shaft and was able to clean up a bit and add some cover to the box. I asked him to grant me some long term  privileges but he was visually uncomfortable with that conversation.

As to cost of the thing, I don't think it  makes any difference to him if it is replaced or fixed, they don't make money on selling stuff. I think it would be much more difficult to convince him to install repaired item If they did.

[Assafl]

I would consider using conformal coating to protect the board. In Europe something like Plastic 70. Mask all connectors and do a few layers (I bake them in a 70 degree oven for an hour between layers).

One of the possible reasons the elevator guy was not happy is that elevator parts typically have safety functionality. Door controllers are usually listed under safety components. While not as important sounding as speed governor (the weird small wheel in the elevator machine room) - or the safety breaks - door malfunctions were responsible for a few elevator accidents.

For example, a door controller may limit the current to the motor to avoid pinching (which may have been taken out of calibration). May signal to the controller that it is safe to travel if the door is closed. May have protection timers if the door doesn't close/open in time. Sense if something is stuck in the door (like the hand of a small child or the leash of a dog) Etc.

In elevators, usually there is more than 1 safety - but using a repaired board whose safety features were not tested may pose a risk and may be an insurance liability.

There are few elevator accidents. See: https://en.wikipedia.org/wiki/List_of_elevator_accidents

BTW Even white goods: whenever you repair a white good (e.g. a dishwasher) keep in mind the possible "safety" implications. For example, if you repair a dishwasher pressure sensor using non-identical parts (which may be much cheaper than BSH or SMEG sourced components), you may be inviting flooding (yes - there is a float that will prevent that - but you went from having two safeties to 1). An overheating oven may be a fire risk. Etc.   

[timeandfrequency]

I would consider using conformal coating to protect the board. In Europe something like Plastic 70. Mask all connectors and do a few layers (I bake them in a 70 degree oven for an hour between layers).
[...]
There are few elevator accidents. See: https://en.wikipedia.org/wiki/List_of_elevator_accidents

CRC/KONTAKT CHEMIE Plastic 70 is for sure a suitable product for protecting the board.
The elevator accident list is unfortunately incomplete.

[Assafl]

The elevator accident list is unfortunately incomplete.

Poor kid. The entire weight of the cabin (and the hydraulic ram) was on his chest.

The operative concept in this case was that hydraulic elevators (which are usually very safe) are rare in France. ("L'ascenseur, de type hydraulique, rare en France,...").

So the technicians are not as experienced in their maintenance. Furthermore, they are not as "up-to-date" as to updates to ASML standards. So they end up using parts (old spare parts stock) that may have been identified as "unsafe".

The problem with "Safety" is that for the most part it isn't obvious. Why double check valves when one will do? An additional safety timer that never engages in a controller box? An "out of place" switch that seems to do nothing? An unidentifiable component?

From the outside a "safety relay" looks and works identical to a regular contactor. So why spend 10x on a force-guided safety relay? Also - what are the downstream effects if you use the wrong component? (if you are lucky you burn the motor; if unluck the elevator falls or the door severs someone's head).

[PiotrMisiuna]

I think it is a matter of trust. I'm not a teenager thinking about lift-surfing. I am a technician with years of experience who wants to look after our equipment in our building. If a certified guy from outside company doesn't believe I can handle basic procedures, I respect that.
Trust goes both ways thou. Now I only have more questions about why a 1000 euro part has to fail when it wouldn't if properly taken care of.
I'm too busy to thing about it too long. Passed my thoughts to the building owners and they will keep that in mind for the future.

Now in a second building I have an elevator that has been offline for 2 years now, and there will be lots more wrong with that. Several companies made it work and it kept on failing after a week or so. That is going to be fun!

[timeandfrequency]

[...]
Now in a second building I have an elevator that has been offline for 2 years now, and there will be lots more wrong with that. Several companies made it work and it kept on failing after a week or so. That is going to be fun!

I have no knowledge about elevators (*) but since they are often controlled by a PLC, checking power supplies, connectors, cables, sensor status and their mechanical positioning is probably part of the basic verification tasks. I hope you will succeed too. Gathering some documentation about that second elevator would certainly be useful to understand the wiring and have some explanation when error codes shiop up. It would be a great achievement that a third-party technician could turn the tide, while elevator repair companies keep stuck on the issue.

(*) first encounter was in this thread 

[PiotrMisiuna]

I did 10000ft assessment of the elevator problem solving a while ago. If you understand electronics well enough you could probably fix it...(huge)BUT!!! The biggest bearer is software. I managed to obtain a manual to the mentioned elevator and many of it's components.
 If you turn on the thing on and self test shows any errors it will lock itself and without access to a proper scanner able to reprogram the controller you can't even troubleshoot the thing, it will stay dead. In some cases you may need multiple devices for doors controllers, motor controllers and other stuff. This topic is huge, dangerous and expensive. Never the less, one day I'm gonna start poking it with a stick.