Electronics > Repair
Prisma elevator door controller, damaged psu, need identify components
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Harry_22:

--- Quote from: Poroit on December 09, 2024, 05:40:24 am ---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.

--- End quote ---

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,


--- Quote from: Poroit on December 09, 2024, 05:40:24 am ---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.


--- End quote ---
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:

--- Quote from: Poroit on December 10, 2024, 05:36:16 am ---Unfortunately not.
It is an SMPS from a 25 year old Air Data Test Set.

--- End quote ---
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.
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