1073dpd power supply

[ljupcopavlovski]

Hi..I have ams neve 1073dpd in not working condition..Its have smps power supply 48v and then on board have 3 voltage regulators..its have 3 measurements points 24v,32v and 5v ..on 32v point i am getting 32v but on 24v its 4.5v on 5v point it is 0.5v..there is sot-23 diode and rezistor involved in regulation but i am novice and i am not shure how to check sot23 diode..please somebady help how to diagnose where is problem..

 

[ljupcopavlovski]

There is closer picture of sot-23 ..A7W 84,or A7W B4 I am not sure  ..I can not any of these chip number on google..

 

[Khron]

http://s-manuals.com/smd/a7

A7W = https://assets.nexperia.com/documents/data-sheet/BAV99_SER.pdf

Are you getting any voltage across C86 (small ceramic near U25 which does the 24V regulating)?

http://www.ti.com/lit/ds/symlink/lm117.pdf

The arrangement looks like the one in Figure 17 (on page 14).

 

[ljupcopavlovski]

thanks for helping..On c86 I am getting 48v..Same like on 32v regulator(which is only workig) on on C87 I am getting 48v..Just on 5v regulator I am getting 1.3v..probably r75 is fried..Tomorrow I will replace it and test again..
on 24v regulator on input its 48v on output 5.2v..

 

[Khron]

The resistor, or the LM317 itself...

 

[ljupcopavlovski]

Lm317 already was changed but there is not change in voltage..I am not sure if this r75 resistor is linked with 24v regulator,its probably current limiter to 5v regulator..

 

[Khron]

That does look a bit "toasty" indeed, but i kinda doubt that's in series with the 5V output (or its input).
That's an 0805 package, usually rated for only 0.125W - at 5V, that'd mean a measly 25mA maximum.

I see a multi-legged chip there in the first photo - perhaps the 24V output needs to be enabled by some supervisor-circuitry?

 

[ljupcopavlovski]

This multileg on picture is  bb pcm4202 thats part of AD..there is datasheet
https://www.ti.com/lit/ds/symlink/pcm4202.pdf
1073dpd has AD conversion board and all these regulators are on same plate with AD conversion..there is wider picture..