3v LED not lit

[deplanche]

Photos of the boards

[RJ]

After some other projects this summer and fall, I am finally getting back to this now that it is decorating time (and I remembered it wasn't working).

I checked the two legs of the LEDs with the voltmeter, and when they should be coming on with the test function, I measure a voltage of 1.62 V.  I did check all of the LEDs with a button battery, and they all seem to be in the correct orientation, so I am pretty sure that is not the problem.

I also put a voltmeter on the legs of the two regulators.  The one has 8V on one leg and 5 V on the other.  The other has 5V and 2.42 V.

Any thoughts on what could be wrong?  I have two boards with the same problem and are measuring the same voltage within 0.02 V.

Jon

Ok is this a Ver 4 Express?  Sorry you have to bring me back up to speed. Could it be the 3v reg problem we found on the Ver 4 if so then I have a couple new 3.3 v regulator for you that will fix it on both.

RJ

[RJ]

Ok you posted at the same time I was.

Yes this is a known issue just pm me and I will help you fix this proto.

RJ

[RJ]

Wait,,  What 3.3 v reg is that?  did it come in a coop or is this a sub part?

RJ

[deplanche]

I got the original 3.3V regulator with the coop.  Was having a problem with the 3V led not coming on (see original post) so you sent me the 3.3V (one for each board) that I installed as show in the photos.

[RJ]

Ok so you have the updated regs and still have an issue. Does the unit work and not 3.3 or it is non functional and has no 3.3v?

RJ

[RJ]

Ok pardon my confusion I had to get caught back up. Work with 50 people since then.
So if I understand we have power including 5v & 3.3v leds now but the leds on the channels do not light up and no control.

If this is not correct let me know please.

The optos are in the correct direction

I still worry about the leds being backwards. You say you check them with a battery but which side are you putting the positve of the battery. The side toward the pic is -  and the lead on the dise facing the opto or bottom of the board is +

Power comes throught the opto and when the pic grounds the top of the led it turns on allowing current to flow which makes the opto trigger.

RJ

[deplanche]

No problem about the confusing.  Been catching up on reading here while waiting for posts and see you have been a busy guy.

In the current state, both the 5V and 3.3V leds light up, thought he 3.3V does look a little dimmer than the 5V, but I couldn't say by how much.  Both those stay lit all the time.  However, no other LEDs light up when i go into the test mode.

The LEDs on the channels will light if a hold a battery to them in the same orientation as the 3.3V LED, but not the 5v LED.  I think that means they are in correctly from what I can tell anyway.

[RJ]

Ok so let me give some thoughts on this.

Two things I have picked up on give me a thought, You say the 3.3 led is dimmer than the 5v, and you took a reading on the 3.3v reg and got 2.42 which is not correct and should close to 3.3v :

So I am going to say you have a short as in a bridge bad componet ect.

Lets work thought to the answer for you. One there are a few solder joints that I can not see clear on the bottom but unless the clur is getting me they look like they are possible bridges. First look them over very closely and if they are questionable then fix them.

If this yields no results then do this :

Pull the two st485BN 8 pin communication chips out of the pcb and then pull all 16 of the opto 6 pin chips below the led out. check the voltage on the 3.3v reg again to see if you get 3.3v or very close.

I you do you begin inserting one chip at a time and checking the voltage. If you find a big change with one you likely have a damaged chip so leave it out.

If on the other hand you pull them and still have low voltage on the 3.3v reg then pull the rest of the chips and check.

If you pull them and still have low voltage then it is a bridge and must be found.

Let me know how you make out and what you find. If you need at that point we will setup a voice chat and work to the solution.

RJ

[deplanche]

Touched up all joints with a hot iron, and inspected them with a magnifying glass, and I don't see any shorts/bridges.  Can't see the underside of the sockets from the top of the board thought, obviously, so something could be hiding there.  That didn't help.

Pulled all chips and still only have about 2.48 V on the one leg of the regulator. 

Did this for both boards and am getting the same results.

I am wondering if I installed something wrong.  Something backward or in the wrong location.  A solder bridge on one I could understand, but on both and giving the same problem seems like it is something wrong on the assembly.  But I could be wrong on that. 

Thanks again for all the help thus far.

Jon

[RJ]

Can you get into teamspeak so I can help?

RJ

[deplanche]

I am in the chat room from the link at the top, but no one is in there.  Is teamspeak something else?

[RJ]

I am in the chat room from the link at the top, but no one is in there.  Is teamspeak something else?

Yes but stay put!

RJ

[deplanche]

The new 3.3V regulators did the trick.  Thank you!!!

[RJ]

Great!

Now if we could over come the mystery of the other ones and where they came from 

RJ