SMPS MeanWell AD-155c - Buffer PSU - no voltage on output

[K4masz]

Hello everyone, recently I have received this old power supply from my friend. I decided to repair it, not for the money but mainly in order to gain some knowledge and maybe a working device

OK, The main symptom is a fact that there is no output voltage.

The things I managed to determinate so far:

• The bulk electrolytic capacitor [400V] - charges.
• PWM&PFC IC receives voltage (output not tested).
• Two optocouplers are working properly.
• Two fuses are not blown

• Friend gave me piece of advice to change one of the fuses with light bulb - its behavior told me that there might be short on cold side

[/list]

I am very open to suggestions about where to look for point of failure.

The PWM&PFC Combo IC is FAN4803 - it is located right above main transformer

IC on the right of the main is Dual OpAmp - AHA17358 B

[PKTKS]

Well this is not just a simple thing...

First 2 cents of rant:
-  I have just overlooked that not very common supervisor
- In the present days PFC has become kinda BUZ market thing - yet another one
- That PSU is just barely 150W if that much - PFC is nonsense thing with that power
- PFC puts a long list of complicated things to check in something (SMPS) already complicated
- With 2 optocouplers I will expect more than 2 error amps and independent FB loops
- sum that with a fairly complicated soft start required by that PFC chip what you have?

You have a somewhat complicated (and patented) CURRENT MODE (ISENSE pin) soft
start (very low power)   SMPS **WITH** PFC bundled...

just for the sake of patent incomes and that PFC BUZ thing.

After the rant the advice or steps I would "try" ..
- to have a clear view of what sort of messy topology that 2 optocouplers
  are driving back to the supervisor..
- if that supervisor is able to soft start something... or not

It looks a rather complicated setup to a rather humble power class of less than 200W.

In cost x time issues I would ditch that for a far more capable PSU
and probably much cheaper.. 

 **ANY**  S-360-60  based on 494  clones  is below  U$30 tag
that almost double rated 360W with true 10A output.

30box?  I would not bother that crappy PFC patented and probably expensive chip...

I would ditch that for an s-360W or better..  and save the hassle

Paul

[magic]

What's that "battery low protection: 39V"?

[mikerj]

What's that "battery low protection: 39V"?

This unit appears to have some kind of UPS function, and has a secondary output for battery charging.  The datasheet is pretty vague on the operation of this however.

[magic]

Yes, I'm reading the same datasheet The question is of course could it be causing the unit to shut down in absence of a battery.

Other than that, main capacitor charging indicates that the PFC works and the primary switching FET isn't shorted. Most likely the driver is OK too because it's part of the same chip as PFC. So probably the secondary is commanding a shutdown for some reason or malfunctions.

[PKTKS]

if they follow that diagram published the 2 optocouplers
are just for the over protections  unless you have some
sort of TL431 near those..

in case the supervisor is unable to soft start those
protections or would  be  faulty or they have nothing to protect

With the PFC being CURRENT MODE driven and highly
dependent on that "patented" soft start "single pin"..

I would guess that the PFC is not able to start ..

Geezzzz this unit costs U$85 delivered

An s-600-60  cost U$ 35 (delivered) an s-360-48 or s-360-36 not even this
and they all can charge any battery the same way...

and you can fix any S-xxx-xx series very cheap either...
the parts are easily found

hmmm that PFC chip seems  a hassle
Paul

[K4masz]

I actually have a second unit which seems to work properly.
The diode is alive, and the output voltage on standard output and battery one can be manipulated in range 45V-61V. I haven't tested the current.

Can I use this working one to somehow determine what may failed in the broken one?

[PKTKS]

Can I use this working one to somehow determine what may failed in the broken one?

Yes you can

draw a concise list os parts with locations and references

Measure the voltages at proper  KEY POINTS
(deciding what is a key point is your great challenge)

BE VERY CAREFUL BECAUSE SOME POINTS MAY HAVE about 1KV (spikes)
** DO NOT MEASURE THE SWITCH or FLYBACK PRIMARY DIRECTLY **

it will damage your instrument quite easily

that said you have the secondary and the IC voltages
w/ care about the primary pulses...

take note and dup the procedure on the failed unit
with some luck you may have a very good start point clue or direction

Paul