power supply BK1550

[J4e8a16n]

Hi,

The Current Limiting feature does not work anymore on my 2 years old  BK1550 Precision  power supply.  I paid 160$ on Digikey and I wonder if it woth the effort.

I am looking at the schematic helplessly.

Thank for your attention,

Jean Pierre

[mij59]

Hi,

Of course its worth the effort.

Start by opening the power supply and look for clue's e.g. bad solder joints, lose connectors, burned components etc.
Please post some photo's of the pcb's .
Check the supply voltages e.g. 9V+, 9V-, VCC, VREF .
The opamp U3A and the opto coupler PC2 are  part of the current limit function . 
Got page 2 of the schematic ?

[J4e8a16n]

>Check the supply voltages e.g. 9V+, 9V-, VCC, VREF
For the lm358?
Unfortunately I have open the PS for photographs.

If you dont need more photographs, I will put the parts in place to take the readinds.

JP

[mij59]

Unfortunately I have open the PS for photographs.

Why is this a problem ?

Did you measure the supply voltages 9V+, 9V-, VCC, VREF ?

[J4e8a16n]

Here are the voltages.

The main output voltage vary under load. For example 2.9 volts & .03A  on a 12 V light goes to 1.6V.

A better photograp of the board.
JP

[mij59]

Here are the voltages.

The main output voltage vary under load. For example 2.9 volts & .03A  on a 12 V light goes to 1.6V.

A better photograp of the board.
JP

So there's also a problem with the output voltage of the power supply.

Sorry, but no relevant information is presented, non of my questions are answered.
Can not proceed this way.

[J4e8a16n]

Hi,

>Are not your answers about VREF VCC etc.  in the pdf file uploaded?
>Did you measure the supply voltages 9V+, 9V-, VCC, VREF ?
Answers  about the multiples vref vcc and 9 volts   on the schematic in the pdf in the   --Reply #4 on: January 12, 2015, 05:07:07 AM »--   .

+9 -9       8.99
+9           3.3
vcc           12.13  12.17
VREF         1.932     4.5  2.559


JPD