Pioneer VSX-1122-k shorted V+3.3_HHH rail

[tibimakai]

I had this receiver for a while.
I have picked it up from the bay(it was dead), with box and all the accessories.
It's almost new.
A while back I have worked on it, with help of some folks here, but we couldn't find anything wrong.
Now, I have pulled it out again and I have noticed, that this 3.3V rail is shorted.
Shows 1.6 Ohm, at many components.
The question is, how to find the shorted components?
I have tried usind the Ohm meter(Fluke 189) and I have found Q901 at 1.55 Ohm and IC610 at 1.54 Ohm.
I have even removed these and checked the components around them but, I could not find anything wrong.
I would use a thermal camera, but I don't have one yet.
I have borrowed one for like two days, but I couldn't really find the overheating part(couldn't see the parts through the camera). Something between the Ethernet port and IC1602 get to 106 F degree, but I couldn't pinpoint which part it was. I have even removed that IC, IC1808, D1601, but short was still there.
Any suggestions would be appreciated.

[tibimakai]

Re: Pioneer VSX-1122-k shorted V+3.3_HHH rail

The problem is on the HDMI board.
Elektrotanya has the schematics.

[CapLeaker]

Re: Pioneer VSX-1122-k shorted V+3.3_HHH rail

It's probably a lightning special then. Good chance that it is either the HDMI selector or processor. You could feed the board 3.3V and pump one amp or 1.5A into that rail and see what gets hot. Or you need something like a Leakseeker 89.
Since you have the problem nailed down to one board, can we see both sides of it?

[tibimakai]

Re: Pioneer VSX-1122-k shorted V+3.3_HHH rail

Which are those ICs? IC9602 and IC903?
I will take those pictures, when I get home.
I have tried injecting power at high amperage, but I couldn't tell what is getting hot.

[CapLeaker]

Re: Pioneer VSX-1122-k shorted V+3.3_HHH rail

Service manual page 76, D 3/10, there is the IC903. Top left is the 3.3V HHH rail. Then there is the inductor L902, lift a leg or take it out and see if the short goes. Same thing for L905 (left of the IC903, page 77.
When I looked at the schematic of the D-Main ASSY, most IC's had an inductor on the 3.3V HHH rail. If you look at page 18 block diagram, I'd go for disconnecting the 3.3V HHH rails on the Sil9387A and the Sil9233A first. They have at least two VCC feeds per IC.

[Longbow]

Re: Pioneer VSX-1122-k shorted V+3.3_HHH rail

You could feed the board 3.3V and pump one amp or 1.5A into that rail and see what gets hot.

Glad you mentioned this technique. I wouldn't pump any specific current as it risks smoking other parts along the line. With care, you can isolate a supply rail, usually +5 or +3.3 volts, from the rest of the circuitry and connect it to an adjustable regulated supply. In previous lifetimes, good practice included adding small ohm isolation reisistors to each stage connected to a common rail. You don't see those resistors used that much these days. Gently raise the voltage on the shorted line (keeping it well under its normal voltage). The faulty part will heat up with very little voltage in no time and you will save yourself further smoke and board destruction, also avoiding the job of pulling parts out.

Another technique that sometimes works is the use of a meter that will read very low ohms values. This method takes into account the resistance of the pc traces. With one probe on ground, you can isolate a shorted part by moving the positive probe along the rail. The lowest reading will locate you closest to the shorted part. Just a thought.

[tibimakai]

Re: Pioneer VSX-1122-k shorted V+3.3_HHH rail

I have found the lowest resistance, at Q901 and IC610. But even after removing these, the short it was still there.

[CapLeaker]

Re: Pioneer VSX-1122-k shorted V+3.3_HHH rail

Keep on isolating on the 3.3V HHH rail until you got it. There may not only be one component bad, could be multiple. Could you test the components you took off for a short?

For example: Right now I have like 5 Nortel CICS phone systems here to repair. One of them has a short on the 5V rail in the area where the CPU's, memory and the hardwire switch is. The memory, both CPU's and the hardwire switch are shorted and I have taken off the board, but still got a short on the 5V rail. There are about still two dozen little IC's around. Time to get the Leakseeker 89 out.

[tibimakai]

Re: Pioneer VSX-1122-k shorted V+3.3_HHH rail

You may be right, but unfortunately I have soldered those parts back, two days ago.
I have almost screwed up IC1808. I have broke off somehow, pin #5. Luckily it is not used. I have created a short between pin #3&4, but those are all ground(luckily). It is hard to work, with such a small IC, next to a big Ethernet port.
I don't have a Leakseeker 89.
Last night I did not work on it, I had to repair Windows on my daughter's laptop(she is 8).
I took some quick phone pictures, though.

[Longbow]

Re: Pioneer VSX-1122-k shorted V+3.3_HHH rail

First, zero your meter probes. Are you reading less than 1 ohm on the rail to ground? Has your 3.3 volt regulator been disconnected from the board? Nothing gets hot? If that is so, then you probably have a solder bridge or stray wire accross the 3.3v. supply rail. Not many parts can go to 1 ohm or less. A smashed HDMI or other panel connector could cause this type of direct short.

[tibimakai]

Re: Pioneer VSX-1122-k shorted V+3.3_HHH rail

I'm at work right now, but I can check later.
I read between 1.54 and 1.67 Ohm on the 3.3V rail.
3.3V regulator is on the board. I have replaced it, since I have removed it for testing.
One time I tried with external power supply, but I did not check out each component. At that time, I did not notice anything getting hot.
I will try it again, hopefully today.

[madan1]

Re: Pioneer VSX-1122-k shorted V+3.3_HHH rail

shorted caps?

[tibimakai]

Re: Pioneer VSX-1122-k shorted V+3.3_HHH rail

I have tried at that time, injecting power from my power supply, and with a thermal camera I could see something getting red next to the IC903(around X901), but I could not see clearly enough on the camera, which component it was that.
Unfortunately, I had to return the camera and now, I'm "blind".
I'm thinking, that I should buy a thermal camera, nothing expensive though. I'm thinking Flir TG167(narrower field of view, then TG165(suggested by Flir), or if I could find a Flir C2. Recently was sold one on CL, for $250. Maybe even a TG130.

[madan1]

Re: Pioneer VSX-1122-k shorted V+3.3_HHH rail

Use thermal printer paper .
fix it to the pcb and let the juice flow... It will get dark on the hot spots ( 70*+ C ).

[tibimakai]

Re: Pioneer VSX-1122-k shorted V+3.3_HHH rail

Eastern European ingenuity, at it's best. I'm originally from Romania, but I'm Hungarian.

[CapLeaker]

Re: Pioneer VSX-1122-k shorted V+3.3_HHH rail

stick to cutting the 3.3V HHH rail to all the IC's by removing the inductors. You could also feed it power again and douse a suspected area with 99% alcohol. If something gets hot, the alcohol will evaporate faster.

[tibimakai]

Re: Pioneer VSX-1122-k shorted V+3.3_HHH rail

OK, short is gone, by removing IC903, after removing the inductor. Clearly, the short it was on the IC's side.
Aplied power and the IC started to warm up. I have noticed, that other componentswere getting warm as well. 1.2V's capacitors.
Recever still won't atart up, though. The 3.3V is still not there yet, it is only 0.8V. Need to investigate a bit more. Did not have more time.

[CapLeaker]

Re: Pioneer VSX-1122-k shorted V+3.3_HHH rail

I figured that it was a lightning special. Congrats for finding the short. Right now there a 2 things: Either the 3.3V HHH rail regulator is bad, or other IC's are shorted in a different manner, drawing more than the regulator can handle.

[tibimakai]

Re: Pioneer VSX-1122-k shorted V+3.3_HHH rail

It seems like the 3.3V regulator had some issue, because after I have replaced it, when I release protection mode goes up to 3.3V.
Unfortunatelly, still won't boot up completelly.
But, we are a step closer to a full boot up.
The display turns on and shows SAT/CBL and then stuts off.
There is no error or anything. Everything is connected, except some ground straps from the front panel. What should I look for now?
With the HDMI chip removed, it should still boot up, or that may be the problem?
Final transistors are not shorted, in the amp section.

[CapLeaker]

Re: Pioneer VSX-1122-k shorted V+3.3_HHH rail

You are making good progress!


I guess it won't start, because the IC is missing. After all the SIL9233A is the main HDMI processor, where the SIL9387A Port processor feeds into it too. So basically the main CPU is supposed to find the HDMI ports and you have zero. You also may have to factory default and may have to reload firmware after putting a new IC in.