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[wilgo45]

Got a Jasper board I am trying to rebuild.

No mods at all.  Completely Stock.  In pretty good shape.  Just needs component replacement.
It has a short between the 12v line and Ground.

Found one bad N channel FET and removed.  Still has short.  Removed all the topside N channel FETs.  All of those are fine.  FETs still off board - and short is still there between the 12 and Ground.

To back up and state  ... the one bad FET was at spot Q6B1

So with all the topside FETs still off ... next I removed a bottom side SOT 223 at Q8N1.  Short is still there.

I am really hoping this is not an issue with the Controller Chip at U4V1.  That sucker is a major pain in the ass to reinstall.

Good suggestions  .... anyone ?

[wilgo45]

RDC recommended removing the Inductor coils.  I have done so.  The short has vanished just with that.

So a bit confused at the moment  ... coils shouldn't be the cause of the short.
Need to go back and check some things

Still open to hearing options.

[wilgo45]

Short is on L8B1's rail.


Never mind the above statement.  It's not correct

This post has been edited by wilgo45: Apr 25 2013, 05:18 AM

[MadMaxGR]

sounds interesting, can you post pics as you go further to the repairs?

[wilgo45]

QUOTE(MadMaxGR @ Apr 25 2013, 03:29 AM)

sounds interesting, can you post pics as you go further to the repairs?

I would if I could.  This forum site doesn't let you post pics directly.  You have to use third party urls

Not signed up with any.  And - no offense - its not on the To Do list.  Suggestions ?

[lessweightgofaster]

Hi, which side of the inductor is still shorting? If you take out the inductors on the 12v rail and the fet side of the inductor is open circuit then it must be on the smoothing side of the inductor maybe a shorted cap?
 Can you compare the resistance between a good board and yours?

Soz cant be more help, i know its mega difficult find random shorts on boards, spent many years fixing acrade games!!
Cheers
Ian

[wilgo45]

thanks lessweight for chipping in

Still searching and making attempts.

I must be making some errors in my testing procedures.

So  ... to back up - when the Inductors were still installed, the short between 12 and Ground was evident.  And at this time, all the N channel Fets are off.

With the coils off - I essentially lose the bridge - so the short drops.  So its like a false positive.

And checking the remaining transistors has turned up nothing yet.  Perhaps it is a Cap.  Would you think Electrolytic or Ceramic ?

[wilgo45]

OK ... much thanks to lessweight

I think I have some progress.

The short is on the L8B1 line.  And I think I have found about 5 ceramic caps that have shorted.

These ones that are all culprit: C8B4, C7B2, C7B4, C6B2, C6B5

[wilgo45]

Full progress averted.

I did find some shorted ceramic caps.  But after removal - there is still a short in the L8B1 rail.

Before it would 0.0 ohm on testing.  Now, it shows 15 ohm between GRD and 12 - after all that has been removed.

Wondering if its a short in the Cpu chip itself.  That is showing nearly 15 ohm when the caps to the right of it are probed.

More suggestions  ... anyone

[MadMaxGR]

QUOTE(wilgo45 @ Apr 26 2013, 08:43 AM)

OK ... much thanks to lessweight

I think I have some progress.

The short is on the L8B1 line.  And I think I have found about 5 ceramic caps that have shorted.

These ones that are all culprit: C8B4, C7B2, C7B4, C6B2, C6B5

I am very interested on your progress because I have a Falcon that is pain in the ass. It was working great and one day when I opened it up to clean and just replace thermal paste... became a dead brick. It is shorting somewhere and when I have time I will follow your steps

P.S. you can use the tinypic.. is fast and easy, no registration needed.

[wilgo45]

QUOTE(MadMaxGR @ Apr 26 2013, 03:22 AM)

I am very interested on your progress because I have a Falcon that is pain in the ass. It was working great and one day when I opened it up to clean and just replace thermal paste... became a dead brick. It is shorting somewhere and when I have time I will follow your steps (IMG:style_emoticons/default/smile.gif)

P.S. you can use the tinypic.. is fast and easy, no registration needed.

PM'ed you

tinypic ?

[MadMaxGR]

Yes tinypic.com

[lessweightgofaster]

Hi, pleased your getting there, if your getting 15ohm across the cpu i would think that would be fine, sumtimes cpu's have a small resistance due to the amount of current they draw, i measured a pentuim once think it was 8 ohm on one of power rails, i'd bung it back together and see wat happens, just keep an eye on the resistance and see if it changes much.
You could always bung a led on the line so when its powered up you can see wats going on wthout having to dig around with a dmm.

If your replacing the caps i'd go with a higher voltage ones (but same capacitence)so they'll run a bit cooler if theres room? I not looked at which ones you've taken out yet but will in a bit.

Cheers
Ian

[wilgo45]

My statement on the Cpu chip - causing the short.  That could be wild assumption.

The stronger likelihood would be board device or controller IC.

I feel like I am getting close ... but grasping at straws at the same time.

Problem might even be board structural between the 12 and GND.  There is a spot of mild damage.  The site location of a mosfet gate pad.

IDK

[lessweightgofaster]

These are off a faulty falcon board with 0110
C8D4 8 ohm
c7b2 oc
c7b4 oc
c6b2 oc
c6b5 oc
oc is open circuit
dunno if its much help
Cheers
Ian