DiyLightAnimation

Hardware => Lynx Express => Topic started by: deplanche on July 28, 2010,

Title: 3v LED not lit
Post by: deplanche on July 28, 2010,
Assembling 2 LEs.  Tested both before installing the chips.  Both 5v and 3v LEDs were on for both.  Installed the chips.  Now 3v doesn't light up on one no matter what.  The other will occassionally.  I know it is a chip issue, but before I start pulling all of them, is there a certain one or ones that are more likely to be causing this problem than others?
Title: Re: 3v LED not lit
Post by: RJ on July 28, 2010,
Check the chips one is likely backwards. What version of the pcb?   

RJ
Title: Re: 3v LED not lit
Post by: deplanche on July 28, 2010,
Both v4.0.
Title: Re: 3v LED not lit
Post by: castortiu on July 29, 2010,
RJ can confirm this,

But I had the same issues on 3 LEs V4, if I remember properly the problem was the 3.3V regulator cut off voltage was too high and the output of the 5V regulator was not enough to feed the input of the 3.3V regulator.

I think RJ changed the 3.3V regulator for a regulator with a less cut-off voltage and also works on wider temperatures.

In my case I fixed cutting the input track of the 3.3V regulator and feeding from the same input track as the 5V regulator, the 3 LEs ran fine without problem for 3 weeks that the show lasted, the regulators were a little warmer than usual but not much, barely warm to the tact, still the 3 LEs are working great.

Did you get the component from the coop? and when was it? May be it is a totally different issue but I had the same symptom, without chip worked, with the PIC no 3.3V.

Cas.
Title: Re: 3v LED not lit
Post by: RJ on July 29, 2010,
Yes this is the reason I asked which version. We had an issues with some V4 units and changed the 3.3v voltage regulator to fix it. If you pm me how many units you have and your address I will send you a couple of regulators to change the 3.3 out with and fix it.

RJ
Title: Re: 3v LED not lit
Post by: deplanche on July 29, 2010,
I actually stopped building these because of that problem last fall/winter, and I didn't NEED them for last years display.  I went back thru the posts recently, and since I was ordering some parts from Mouser anyway, got a "511-L7805ABV" to replace the one that was included with the coop back then.  Was that the right part to get, and was it a simple part substitution or did I need to do something else as well?
Title: Re: 3v LED not lit
Post by: RJ on July 29, 2010,
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I actually stopped building these because of that problem last fall/winter, and I didn't NEED them for last years display.  I went back thru the posts recently, and since I was ordering some parts from Mouser anyway, got a "511-L7805ABV" to replace the one that was included with the coop back then.  Was that the right part to get, and was it a simple part substitution or did I need to do something else as well?

Ok that is the issue then.

Shoot me a pm with that info and I will get you a different part that will if it for you.

RJ
Title: Re: 3v LED not lit
Post by: deplanche on August 07, 2010,
Replace the parts with those that you send.  Both boards now have both power LEDs lit when plugged in.  Bad news is that when I run the test, i get the LED display to light up all the way to the "888" then "tst", but none of the channel light LEDs come on.  This is true for both boards.  So I think I still have something not quite right.  Any thoughts?


Edit - I am pretty sure, but not 100% positive the one that was intermittently working before was able to run the test fine when working.  So I don't think I have the LEDs in backwards or anything like that.
Title: Re: 3v LED not lit
Post by: RJ on August 07, 2010,
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Replace the parts with those that you send.  Both boards now have both power LEDs lit when plugged in.  Bad news is that when I run the test, i get the LED display to light up all the way to the "888" then "tst", but none of the channel light LEDs come on.  This is true for both boards.  So I think I still have something not quite right.  Any thoughts?


Edit - I am pretty sure, but not 100% positive the one that was intermittently working before was able to run the test fine when working.  So I don't think I have the LEDs in backwards or anything like that.

Push the select button.  Does one of the leds light?

RJ
Title: Re: 3v LED not lit
Post by: deplanche on August 09, 2010,
Once it get past the 888 and goes to tst, there is a period after then, when it should be lighting each channel.  But nothing is lit.  And nothing happens when i push either button, I think because it is still trying to light them in the test mode.  If I wait for a minute, and push select button, the whole test sequence seems to start over with the numeric LEDs cycling thru again.

So I guess, my followup question is when should I push the select button for what you are saying in your last post?
Title: Re: 3v LED not lit
Post by: RJ on August 09, 2010,
You gave me enough info!

I have bad news!     <fp.


I am pretty sure you put the leds in backwards   <yk..

Take a digital volt meter and put the leads on the two solder point of the channel number 1 led with the negative probe on the top side of the led and the positive on the bottom side. Then run the test again and watch your meter. I think your going to see the voltage jump each time the led should light.

Sorry if thats the case. I even put a little + on them and a extra note to try to keep anyone from doing that. Let me know and I will give you some advice on how to proceed without damaging the pcb trying to get them out.

RJ
Title: Re: 3v LED not lit
Post by: deplanche on August 10, 2010,
I'll give that a later this week (out of town right now). 

I have been testing most LEDs with a watch battery before installing them too (had 1 blown for another board once and since have been testing before installing).  Would there be any harm in touching the battery to the led on the LE if it was NOT connected to the AC power supply.  That would also let me know if I have the LEDs in correctly I would think.  I always like double checking everything if you counldn't tell. :)
Title: Re: 3v LED not lit
Post by: rm357 on August 10, 2010,
It's also possible that the opto-isolators are in backwards. Can you post a high res picture of the front and back of your boards?

Some of the folks here are very good at catching things like solder bridges and even bent pins...

RM
Title: Re: 3v LED not lit
Post by: RJ on August 10, 2010,
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It's also possible that the opto-isolators are in backwards. Can you post a high res picture of the front and back of your boards?

Some of the folks here are very good at catching things like solder bridges and even bent pins...

RM

Yes I thought of that last night but had already him told him to check with the meter. He is absolutly correct in that the optos backwards would do the same thing.

RJ
Title: Re: 3v LED not lit
Post by: deplanche on November 20, 2010,
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
Title: Re: 3v LED not lit
Post by: deplanche on November 20, 2010,
Photos of the boards
Title: Re: 3v LED not lit
Post by: RJ on November 20, 2010,
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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
Title: Re: 3v LED not lit
Post by: RJ on November 20, 2010,
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
Title: Re: 3v LED not lit
Post by: RJ on November 20, 2010,
Wait,,  What 3.3 v reg is that?  did it come in a coop or is this a sub part?

RJ
Title: Re: 3v LED not lit
Post by: deplanche on November 20, 2010,
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.
Title: Re: 3v LED not lit
Post by: RJ on November 20, 2010,
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

Title: Re: 3v LED not lit
Post by: RJ on November 20, 2010,
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

Title: Re: 3v LED not lit
Post by: deplanche on November 20, 2010,
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.
Title: Re: 3v LED not lit
Post by: RJ on November 21, 2010,
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



Title: Re: 3v LED not lit
Post by: deplanche on November 24, 2010,
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
Title: Re: 3v LED not lit
Post by: RJ on November 24, 2010,
Can you get into teamspeak so I can help?

RJ
Title: Re: 3v LED not lit
Post by: deplanche on November 24, 2010,
I am in the chat room from the link at the top, but no one is in there.  Is teamspeak something else?
Title: Re: 3v LED not lit
Post by: RJ on November 24, 2010,
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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
Title: Re: 3v LED not lit
Post by: deplanche on November 30, 2010,
The new 3.3V regulators did the trick.  Thank you!!!
Title: Re: 3v LED not lit
Post by: RJ on November 30, 2010,
Great!

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

RJ