Help finding schematic for ITE UP30432

[badrianiulian]

Hello
Some time ago I bought a power supply model ITE UP30432 +5V/-5V/+12V 3A/0.3A/2A Power Supply 5 Pin just like the one in this link: http://www.ebay.co.uk/itm/ITE-UP3043...8AAOSw-7RVELkT
Since I bought it, there was a problem with it... it did not power up
The previous owner replaced the 12v shotky diodes with two regular rectifier diodes and I replaced a fuse and two small caps in the high voltage part of the circuit
Right now the power supply powers up intermitently (ticking sound and small voltage variations (12,11v...12,38v and 5.08v...5.19v) and I can't tell what component could cause this
Since I suspect that the previous owner replaced some resistors too, I would like to get the diagram/schematic of the power source to check wether that is the case
Thank you

[stj]

Re: Help finding schematic for ITE UP30432

post pcb foto

[badrianiulian]

Re: Help finding schematic for ITE UP30432

Here are the pictures... these are the best I can do

[stj]

Re: Help finding schematic for ITE UP30432

replace the 2 small caps in the center area.

[badrianiulian]

Re: Help finding schematic for ITE UP30432

Those were the ones I replaced

[stj]

Re: Help finding schematic for ITE UP30432

you have parts not bolted to the heatsink - any reason?

[badrianiulian]

Re: Help finding schematic for ITE UP30432

you have parts not bolted to the heatsink - any reason?

What do you mean... there is the first heatsink that has the mos-fet
There is another TO220 transistor witch did not have a heatsink in the first place in the hight voltage area.
On the second heatsink there are the shotky rectifier diodes.. two for 5V and two for 12V... the -5V has only one small diode on the board and a 7905 regulator

[budm]

Re: Help finding schematic for ITE UP30432

What is the P/N of that 8-pin DIP SMPS IC? Are there any more small electrolytic caps in the primary side beside the two you have already replaced?
What are the resistance reading between the output GND and the +5V, -5V, and the +12V?

[badrianiulian]

Re: Help finding schematic for ITE UP30432

What is the P/N of that 8-pin DIP SMPS IC? Are there any more small electrolytic caps in the primary side beside the two you have already replaced?
What are the resistance reading between the output GND and the +5V, -5V, and the +12V?

The 8-pin DIP IC is UC3842B
No other electrolytic caps are in the primary side
The resistance varies between GND and +5V and +12V... between the GND and -5V is about 8k.
Diode mode:
+ to GND - to 5V = 155, - to GND + to 5V = 833 going up slowly
+ to GND - to 12V =138, - to GND + to 12V = beyond 1999
+ to -5V + to GND = 715, - to -5V + to GND = 1947 going up slowly

[fzabkar]

Re: Help finding schematic for ITE UP30432

The capacitor to the right of the chopper and partly obscured by the output heatsink appears bloated.

[badrianiulian]

Re: Help finding schematic for ITE UP30432

It may appear that way but all the output caps are not bloated ... they look normal

[fzabkar]

Re: Help finding schematic for ITE UP30432

Is it a loading problem? Does the ticking stop if you connect a dummy load to the +5V and +12V outputs?

Is there a sufficient voltage on the supply pin of the IC?

[fzabkar]

Re: Help finding schematic for ITE UP30432

ISTM that the circuit shouldn't be radically different from the application circuit in the IC datasheet.

For example, figure 35 might be close enough for troubleshooting purposes:
https://cdn.badcaps-static.com/pdfs/...9eef16428b.pdf

In addition to the supply pin (7), you could also monitor the feedback pin (2).

[cks hmm]

Re: Help finding schematic for ITE UP30432

good info

[badrianiulian]

Re: Help finding schematic for ITE UP30432

Is it a loading problem? Does the ticking stop if you connect a dummy load to the +5V and +12V outputs?

Is there a sufficient voltage on the supply pin of the IC?

No... when I connect a fan on 12V it does not run at full speed since there are voltage the drops... ticking still there
When I checked on pin 7 of ic (VCC), the voltage varies from 11,7v to 14v... very weird

[budm]

Re: Help finding schematic for ITE UP30432

I expect more lytics caps in the prrmary side than just those two, may be under the heatsink?
Hard for me to trace the circuits due to the heatsink is in the way.

[stj]

Re: Help finding schematic for ITE UP30432

i expect you to bolt things to the heatsink.
red dot = missing bolt

dont forget to use an insulating kit.

[budm]

Re: Help finding schematic for ITE UP30432

That one without the heatsink looks to be fed by the AUX Voltage from the AUX winding. Vreg IC?

[badrianiulian]

Re: Help finding schematic for ITE UP30432

Here are more pictures:

[badrianiulian]

Re: Help finding schematic for ITE UP30432

The one without a heatsink is a BUZ71A 13A/ 50V/ N-Channel Power MOSFET ... it is fed by the AUX winding
Vrev is variable from 0,3V to 1,4V