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Re: R15 and ADE-1 mixer getting very hot

Mvs Sarma
 

William,
Don't feel lost. afterall thase things happen.
as you took out the ADE-1, once, do it again
?while it is out, using datasheet for pin id, test cross insulation bteween winding 1-6
?to other windings like 2-5 and 3-4
?the meter should show meg ohms
?if there is a short, it would be between 2-5 and 3-4
?but not to 1-6.
?after ensuring that you can mount.
?I fear that 1-6 is getting shorted to ground after the winding.



On Thursday, 27 April 2017 5:27 PM, William Hemmingsen <lee.hemmingsen@...> wrote:


I checked all the traces, an I see no bridges.? I removed the ADE-1 and shorted pin1 to 6 using a wire.? Now no longer does R15 get hot.? So that eliminates anything in that path.? So that leads me down the ADE-1 rabbit hole.? I suspect current is flowing from ADE pin1 to ground when 12v is applied.? I checked the resistances from ADE pad pin 2 & 3 to ground and they open (as expected with blocking caps c18,c19,c11,c15).

But this makes no since, because I have used ADE-1's from 2 different vendors all with same results.? Obviously in the ADE-1 pin1 (primary ground) and Secondary ground are connected.? This send 12v into the pin diodes.? But with no DC load on pins 2 or 3, this should act as an open circuit for DC.

Now I'm really lost


W4WHL

On Thu, Apr 27, 2017 at 6:24 AM, Lawrence Galea <9h1avlaw@...> wrote:
Check for a solder bridge or a tiny copper trace that remained when the pcb was etched.
You can use a magnifier or a meter to check it.
What you might also do is to run a knife between the tracks to remove any tiny bridge that may not be easily visible.
I also had a piece of equipment where the pcb would short after some time and if you switch off and leave it for a few minutes it would go open again and then again short after a few minutes.
I had to isolate the respective contact, strip a little bit of track and connect the component a little furtehr because it appeared to be some contamination in the material itself shorting after a few minutes.
You learn by experience when things do what they shouldn't do.
Regards
Lawrence

On Thu, Apr 27, 2017 at 2:47 AM, William Hemmingsen <lee.hemmingsen@...> wrote:


R15-c17 junction to ground is 13.3k.? I removed c17 and no change.? FYI R11 & Q7 are also removed.? So this resistance is 100% in the ADE-1 itself (as its the only thing left).

If I recall correctly, when R11 is in the circuit the resistance is 2k as expected.

Even with R11, Q7, C17 out of circuit R15 gets burn you hot when you apply 12v.

Also my ADE-1 is mounted the same as your attached picture.

I took a brand new ADE-1 from reel and measured resistance from pin 1 to 2 = 20k? & pin 1 to 5 = 40k.? if I remove R15, the ADE-1 on the board matches this.? This makes no sense, because those resistances should limit current.? My guess is the resistance goes down when the diodes are biased...Just a wild guess.? But when 12v is applied R15 heats up like there is a short.

With all components installed; When power is applied I measured the voltage at R15-c17 junction which equals only 1.5v (it should be close to 12v correct?).? Gate voltage of Q17 is only .7v. ? So this would leave me to guess that when power is applied the ade-1 must go to ~12 ohms to drop the voltage that much.

I'm lost

W4WHL




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