[BUILD] CAPI Dual VPR & 51x Floor Box PSU~Official Support Thread

[kante1603]

+1 on Jeff's comments!
Zooming in to pic 1 it looks like you clamped the insulation,not the wires.
Especially visible on the left green one.
Also the tinned leads don't seem to have any visible markings from pressure,they might have never seen the "force" to make a good contact.


Best regards,


Udo.

 

[rafael-sf]

Hi folks, I just finished building another PSU and VPR chassis and all the voltages look good. But when I plug the DC cable and flip the switch on the PSU, the 48V fuse goes. I took the back of the chassis out and visually inspected the solders and they all look good to me. Any suggestions on how to chase this one down? I've built/repaired a few of these over the years but don't remember having these kinds of issues.

Thanks,
Rafael

 

[jsteiger]

Hi folks, I just finished building another PSU and VPR chassis and all the voltages look good. But when I plug the DC cable and flip the switch on the PSU, the 48V fuse goes. I took the back of the chassis out and visually inspected the solders and they all look good to me. Any suggestions on how to chase this one down? I've built/repaired a few of these over the years but don't remember having these kinds of issues.

Thanks,
Rafael

Have you checked for shorts from 48V to ground in the rack with a DMM? Is the rack empty or loaded when this happens? Is it a 51x 18-pin rack?

 

[gar381]

Remote possibility but I have seen this happen.... :'( 

If you are firing up a rack full of pres and all the 48v Phan switches are turned on on the pres, 
The in-rush current charging up the 48v Rail caps on all the pres at the same time takes out the fuse.

Hope you find the problem 

GARY

 

[PetezaSlice]

These are the measurements I'm getting in the power supply

+48v: 48.2
-16v: -02.8
+16v: 02.8
+V#2: 02.8
-V#2: -02.6
+48v: 48.2


Why am I not getting 16v reading? only 2.8v.

 

[jsteiger]

These are the measurements I'm getting in the power supply

+48v: 48.2
-16v: -02.8
+16v: 02.8
+V#2: 02.8
-V#2: -02.6
+48v: 48.2


Why am I not getting 16v reading? only 2.8v.

My first guess would be you have some resistors accidentally flipped/swapped around.

 

[PetezaSlice]

what do you mean flipped/swapped around? ie, I have them in the right resistor position but their polarity is wrong, or do you mean I placed some resistors in the wrong position?

 

[jsteiger]

what do you mean flipped/swapped around? ie, I have them in the right resistor position but their polarity is wrong, or do you mean I placed some resistors in the wrong position?

Direction doesn't mater for R's. I mean maybe 243R's got used instead of 2k43's.

 

[PetezaSlice]

Yes I think that is indeed what happened. you are spot on, 243s for 2.43k

 

[PetezaSlice]

Okay so 2.43ks are in the 243r spots, but in the 2.43k (red, yellow, orange, brown. brown) spots are 240 (red, yellow, black, black, brown).  I can't find 243 which would be red, yellow, orange, black... wouldnt it?

 

[rafael-sf]

Have you checked for shorts from 48V to ground in the rack with a DMM? Is the rack empty or loaded when this happens? Is it a 51x 18-pin rack?

Hi Jeff, the rack is empty and it's the 15 pin VPR. I do see pins 1 and 5 are shorted, it looks like my DMM charges one of the capacitors when I measure between those two (either at the neutrik connector or any of the 15 pin connectors). I cleaned up any suspicious looking solders but still seeing this.

BTW, can I use a 250mA fuse instead of a 160mA? They're easier to find around here.

Thanks,
Rafael

 

[jsteiger]

Hi Jeff, the rack is empty and it's the 15 pin VPR. I do see pins 1 and 5 are shorted, it looks like my DMM charges one of the capacitors when I measure between those two (either at the neutrik connector or any of the 15 pin connectors). I cleaned up any suspicious looking solders but still seeing this.

BTW, can I use a 250mA fuse instead of a 160mA? They're easier to find around here.

Thanks,
Rafael

You need to check from card edge connector pin-15 to pin-5. Make sure the 48V rail is not shorted. 250mA can work in a pinch but I don't think we can recommend it long term.

 

[rafael-sf]

You need to check from card edge connector pin-15 to pin-5. Make sure the 48V rail is not shorted. 250mA can work in a pinch but I don't think we can recommend it long term.

Sorry, that's what I meant. I see the same behavior when measuring pin 15 and 5 on the edge connectors. But I don't see anything on the board that would cause this. Any idea what could be doing it? Desoldering some of these things will take forever.

 

[PetezaSlice]

is there a reason I have r240 and not 243?

 

[[silent:arts]]

is there a reason I have r240 and not 243?

240R or 243R - doesn‘t matter  (but need to be in the right place on the PCB)

 

[jsteiger]

Sorry, that's what I meant. I see the same behavior when measuring pin 15 and 5 on the edge connectors....

You measure a direct short between those card edge pins 5 and 15? With the PSU cable disconnected from the rack?

 

[rafael-sf]

You measure a direct short between those card edge pins 5 and 15? With the PSU cable disconnected from the rack?

Not a zero resistance short, it looks like the short is going through a capacitor (resistance climbs as I start measuring it).

 

[PetezaSlice]

For the 5pin xlrs for VPR, numbers on the cable leads correspond to  xlr pin numbers? Or does green/yellow go to 1?

almost there. My corrections fixed problems, I was a little bit worried I wreck a couple of the PCB hole leads... but everything seems to be working, all LED lights are equal brightness and measurements then became 16.2 (adjusted to .7).


--
I  think I got it... Green/Yellow gets clipped as does 6, and then 1-5 leads goes to 1-5 pins, correct?

 

[rafael-sf]

For the 5pin xlrs for VPR, numbers on the cable leads correspond to  xlr pin numbers? Or does green/yellow go to 1?

almost there. My corrections fixed problems, I was a little bit worried I wreck a couple of the PCB hole leads... but everything seems to be working, all LED lights are equal brightness and measurements then became 16.2 (adjusted to .7).


--
I  think I got it... Green/Yellow gets clipped as does 6, and then 1-5 leads goes to 1-5 pins, correct?

Yes, just follow the table at the end of the assembly pdf.

 

[jsteiger]

Not a zero resistance short, it looks like the short is going through a capacitor (resistance climbs as I start measuring it).

Ah, so now I am betting that you have a newer style filtered rack/backplane?? I would check the polarity of the electrolytics on the backplane. Specifically C11 and C17. The two larger 1000µF caps. One of those is likely backwards.