No Dimming on Express

[KeithTarpley]

Greetings,,,

Ok, we have more info now.  You might try flashing the suspect pic in a known good board, just in case the suspect board is keeping it from programming correctly, or in case a curve got into it.

Keith

[pyrodragon97]

just re-flashed it on the good board and it dis to about 30-40% when it should go to zero. Tried setting the curve, but the board never restarts, it just gets stuck in PRG mode

[bisquit476]

You may look at this solder joint, it looks lite on the solder, and I believe it's pin 1 of the PIC. But I may be wrong.

[pyrodragon97]

The solder looks fine. I had gone back and double checked the joints. They all seem ok.

[pyrodragon97]

So I after many hours of frustration I think I'm just going to have to get a new board. I know that the PIC is bad, but can't find a reason as to why the voltage drops to 0 when ramping, even with a good PIC. If any of you have an extra Express board that you want to sell (can be V 4.0) let me know.

Thanks for your suggestions!

[pyrodragon97]

Got another Express from a member. Thanks for your help!

[steve_hirst]

where are you located? maybe a close member could take a look at the board for you.

[TAdamsOK]

From the picture of the front of the board, it looks like the heat sink on the 3.3V regulator is broken and not seated on the regulator properly.  If the chip is tilted forward, which it looks like, you may have an intermittent short where the leg of the regulator come into contact with the heat sink which would cause all sorts of mayhem.  Also any grease that may be hanging around there could be causing a higher resistance bridge if it is a conductive grease and cause the regulator to do some strange things.   

[pyrodragon97]

Just checked and there is no contact with the heatsink. It did snap when I was trying to get the regulator in, but there isnt any contact on the legs.

[bisquit476]

In taking another look at the front of the board, it doesn't look like the shunt is on the terminator, don't know if it makes that much of a difference but something to look at.

[pyrodragon97]

It doesnt. I tried both with it on and off to no avail.

[rrawlings]

I have looked at your board and have found one big thing that has probably contributed to the problems.  No mention was made as to the short you had on CH13.  I noticed that as soon as I looked at your board upon receipt.  next I found one of the vias under the transformer was burnt.  I pulled the transformer and it revealed a huge burn mark.  I am still working my way thru the rest of the board and debugging as I go

[rrawlings]

I should also note that it did still have power but one of the two parallel primary windings of the transformer was not in circuit due to the traces being vaporized.

[chrisatpsu]

was in on backwards?

[rrawlings]

no it was on correctly it appears that there was probably something that shorted from line voltage to the transformer.  There was a burn mark on the board near CH13 output and just the smallest hint of a mark on the the via visible on the bottom side of the board.  At this point it looks like we have correct voltages from both regulators to the pic and to the other chips, the pic is good as well as all other chips as I have swapped them to a good board and they all function.  So at this point I am looking for either a solder problem or another hidden issue resulting from the short.