CAP ID and what to replace?

[redwire]

Re: CAP ID and what to replace?

These kind of shorts are really hard to track down.

Extra techniques to find a short on a rail- Set a benchtop PSU to Vrail at ~1A current limit and inject:
1. Using hi-res multimeter, measure uV drops on pcb (rail) traces.
2. Use a thermal imaging camera to see the hot spot. Works very good, even a few degrees rise can be seen at the fault.

I tracked one down just measuring milliohms with a 6-1/2 digit multimeter with good probes. That turned out to be a short on a pcb ground pour to trace, a copper fleck.

[Mad_Professor]

Re: CAP ID and what to replace?

OK, I forget to ask the actual Ohms reading of the short. There is MLC Cap in parallel with the lytics cap, MLC Cap failure mode tends to be shorted.

Simple 00.3 from 3.3 pin to c702, then 01.0 from c702 to pin 1 of u703.

If you're talking about 3.3 pin to ground pins on the main connector coming from the PSU it's 01.3

[budm]

Re: CAP ID and what to replace?

OK, I forget to ask the actual Ohms reading of the short. There is MLC Cap in parallel with the lytics cap, MLC Cap failure mode tends to be shorted.

[Mad_Professor]

Re: CAP ID and what to replace?

Good idea, but not always a good technique. If the rail is hard-shorted by a ceramic cap, it will take a lot of amps for it to show up and you can burn a trace.

@ Mad_Professor: it's rare for electrolytic caps to go short-circuit. Still, it won't hurt to remove them and check. If not, then measure resistance across all SMD ceramic caps. The ones that give the same shorted reading as the 3.3V rail can be considered suspect. Remove them 1 by 1 until short is gone. If not gone, then it may be a shorted regulator. Before I had a good soldering station, in such situation I would remove ceramic caps 1 by 1, but now that I have one, I remove and check the regulators first.

I understand, but when I put my probes on the cap itself well just the gnd to gnd on other caps it tested short. So when I did gnd to anode on the cap itself it tested short, but there are no other caps after that except for ceramics and I haven't found any other caps that test short on both leads. Usually if I do that, my meter would start at some random and count up until OL, this cap doesn't do that.

"black probe on gnd and my red probe on the two 3.3v and they both are shorted"
What Ohm scale are you using to read this short?
The reason I ask because we have other telling us "the out put read dead short, it shows 0.5 on my Ohm meter". Well, I ask what scale he was using, it was set at 2K scale, so basically, the short is actually 0.5K or 500 Ohms.

I'm using the lowest setting possible, 200 ohms, I also use the same setting to trace it back to c702 and from that cap to the U703's pin 1. Pin3 goes to c749's anode lead *find c774 the print is bad for c749* that cap is a 10v 470uf cap.

I use the diode setting to test the VRM,
1-3 .550
1-2 .098
2-3 .550


But that's still with it in circuit. but the datasheet shows pin 1 to be the V-IN and pin 3 V-OUT. Pin 2 is not even connected, so it must be using it's back plate for a ground, I assume.

That doesn't make any sense, since pin 1 goes to the two pins in the connector marked as 3.3, so unless I'm reading the connector wrong, or pwr is actually the voltage supplier, or I fucked up.

I got some more pictures below.

and yes I'm making sure I have my probes on 3.3 pins and not the GROUND PINS!

circle in red is c702

[budm]

Re: CAP ID and what to replace?

"black probe on gnd and my red probe on the two 3.3v and they both are shorted"
What Ohm scale are you using to read this short?
The reason I ask because we have other telling us "the out put read dead short, it shows 0.5 on my Ohm meter". Well, I ask what scale he was using, it was set at 2K scale, so basically, the short is actually 0.5K or 500 Ohms.

[momaka]

Re: CAP ID and what to replace?

Sometimes, to force the situation I apply 3.3V from an external power supply (at a few amps) and let the culprit get smoked out...

Good idea, but not always a good technique. If the rail is hard-shorted by a ceramic cap, it will take a lot of amps for it to show up and you can burn a trace.

@ Mad_Professor: it's rare for electrolytic caps to go short-circuit. Still, it won't hurt to remove them and check. If not, then measure resistance across all SMD ceramic caps. The ones that give the same shorted reading as the 3.3V rail can be considered suspect. Remove them 1 by 1 until short is gone. If not gone, then it may be a shorted regulator. Before I had a good soldering station, in such situation I would remove ceramic caps 1 by 1, but now that I have one, I remove and check the regulators first.

[redwire]

Re: CAP ID and what to replace?

If there's a short on the 3.3V rail, it is hard to track down. See if anything is getting warm. The Vreg should heat up if one of its loads is shorted.
Sometimes, to force the situation I apply 3.3V from an external power supply (at a few amps) and let the culprit get smoked out...

[Mad_Professor]

Re: CAP ID and what to replace?

Well if they are ok, I decided to look for the voltage regulator. I had my meter on 3.3v pin and accidentally ran my other probe across the shielding of the tuner, and it beeped at me. I thought that was funny so I went to the main connector put black probe on gnd and my red probe on the two 3.3v and they both are shorted, how can VR be ground too, it help me trace it back to L311 G1084-33, but it doesn't appeared shorted, so it must be a decoupling cap near by right?

What's even more funny it's on pin 1 which is ground to begin with. Looks like C702 appears to be shorted, it's JH 220uf 10v, but I can't tell if it's intentional, I will have to remove and test again.

I hope this is the correct datasheet
https://cdn.badcaps-static.com/pdfs/...4ed2bf5adf.pdf

[nnname]

Re: CAP ID and what to replace?

@ Mad_Professor:

They're okay if not running too hot, but not qualitative enough to recommend them as replacement capacitors. Furthermore, the CD263 series has a load life of only 1000 hours for cap diameters of <= 8 mm.

[Mad_Professor]

Re: CAP ID and what to replace?

As "JH" is a brand of Jianghai, the datasheet should be the following:
They are pretty standard 105 °C capacitors.

You can find the matching Elite datasheet here:

Are Jianghai any good?

[ben7]

Re: CAP ID and what to replace?

I'd figure that a voltage regulator probably is busted. Find which one is for the 3.3v

[nnname]

Re: CAP ID and what to replace?

As "JH" is a brand of Jianghai, the datasheet should be the following:
They are pretty standard 105 °C capacitors.

You can find the matching Elite datasheet here:

[Mad_Professor]

I got a bunch of these caps labelled JH cd263, I also got two elites, EJ.

datasheet? what to replace with?

The board is getting 5v from PSU, but pressing the menu panel "Power button," nothing is returned on ps_on. I checked the menu panel, it's not getting any voltages. 3.3v to gnd non-existent even the pwr pin no voltage is received when pressing the button. Checked fuses FB701-704 tested good. So I must have a open or failed cap somewhere, or a faulty voltage regulator on the board.