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TECHNICAL MOTOBRICK WRENCHING In Remembrance of Inge K. => The Motobrick Workshop => Topic started by: flyingbrick.kafe on March 24, 2021, 12:19:45 PM

Title: LED lights
Post by: flyingbrick.kafe on March 24, 2021, 12:19:45 PM: Hello everyone,

I’ve been reading around here and recently registered an account.
I have a BMW K1100 RS that I’m currently working on.

All lights were changed to LED. Front signal light was working with a buzzing sound. But now, it’s totally no sound and light. Did I damaged the relay? BMU mod was recently done but that’s after the lights are not working and it’s still no changes.
Title: Re: LED lights
Post by: johnny on March 24, 2021, 12:29:58 PM: greetings...

it is my understanding 12v led lamps are not reliable above the 48th parallel...

j o
Title: Re: LED lights
Post by: daveson on March 24, 2021, 05:40:35 PM: I'll guess it's only one side, the right side, and that the instrument cluster light works. Since the rear light works it could be an earth failure, front and rear have separate earth's.

I don't think you did any damage.

An earth failure on the right might mean that the cancel switch doesn't work, since it's on the earth side. In that case the cancel switch wouldn't turn off the left indicators, but the auto cancel could still work. If, this fault was before the LED change.
Title: Re: LED lights
Post by: rbm on March 24, 2021, 06:43:44 PM: Sent you a PM.

I think the flasher module is still intact. The BMU has nothing to do with the signals so you can forget that line of inquiry.
Title: Re: LED lights
Post by: flyingbrick.kafe on March 25, 2021, 08:41:46 AM: Thanks all for the input.

@rbm will be helping me diagnose the brick and will update everyone after.
Title: Re: LED lights
Post by: flyingbrick.kafe on March 28, 2021, 02:18:26 AM: So glad I joined this community.
@rbm Robert came in to help me diagnose and we found the problem. One of the fuse was blown and I ended up damaging the relay when I modified it. Robert was nice to lend me his spare flasher relay and will return until my purchase will come in.
Title: Re: LED lights
Post by: Laitch on March 28, 2021, 12:07:23 PM: Quote from: flyingbrick.kafe on March 28, 2021, 02:18:26 AM
One of the fuse was blown and I ended up damaging the relay when I modified it.
Would you describe how you tried to modify it? That might help keep somebody from going down the same path.
Title: Re: LED lights
Post by: rbm on March 28, 2021, 12:35:43 PM: He followed Duck's advice to clip the lead for Pin 7 off of the IC. Unfortunately, this is bad advice, especially when dealing with 8SOIC SMT packages found on the later flasher relays. These ICs are microscopic in size. When flying brick.kafe attempted to clip pin 7 off of the IC body, he accidentally clipped Pin 8 as well. That's not at all surprising since the pin spacing is 1.27mm. A better method of modifying either version of these relays is to cut the copper trace on the PCB leading to the ground. Not only is there lots of room (comparatively) to work in, this sort of modification is also reversible. You can restore the original function of the relay by soldering a jumper wire between Pin 7 pad and ground. Once you cut a pin, the only remedy to restore the function is to replace the IC.
Title: Re: LED lights
Post by: frankenduck on April 10, 2021, 11:26:09 AM: Quote from: rbm on March 28, 2021, 12:35:43 PM
He followed Duck's advice to clip the lead for Pin 7 off of the IC. Unfortunately, this is bad advice, especially when dealing with 8SOIC SMT packages found on the later flasher relays. These ICs are microscopic in size. When flying brick.kafe attempted to clip pin 7 off of the IC body, he accidentally clipped Pin 8 as well. That's not at all surprising since the pin spacing is 1.27mm. A better method of modifying either version of these relays is to cut the copper trace on the PCB leading to the ground. Not only is there lots of room (comparatively) to work in, this sort of modification is also reversible. You can restore the original function of the relay by soldering a jumper wire between Pin 7 pad and ground. Once you cut a pin, the only remedy to restore the function is to replace the IC.

IC chips from the early 90s are “microscopic” in size? LOL. Did you really mean to type that? They’re enormous compared to chips used these days.

Even ham-fisted ole me has managed to cut Pin 7 on numerous flasher relays without issue. Yes, you need to be careful to only cut Pin7 but we’re not talking laser eye surgery here. I find cutting Pin 7 easier than flipping the relay over, making sure to locate the correct pin and then following and carefully cutting the trace. At least for me, cutting the trace takes more finesse and care than cutting Pin 7. (As noted above, I am ham-fisted.)

However, as Chinese cooks are fond of saying, there are many ways to skin a cat and my web page about this has always mentioned that cutting the trace is an alternative method for accomplishing this objective.

Restore the original functionality? Why? To go back to using filament bulbs?
Title: Re: LED lights
Post by: rbm on April 10, 2021, 02:44:11 PM: Duck, This flasher was the second generation that uses SMD parts, not the first generation that uses through hole. Granted through hole DIP pins can be cut using conventional side cutters available to most DIYers. And there's plenty of pin exposed to clip so great finesse is not required though care should be taken. The SMD package for the U243 on the second generation flasher modules is a 8SOIC where the pins are spaced 0.05" (1.27mm) apart and very close to the board. For the average DIYer with conventional tools and little experience, doing such a job accurately is challenging. Conventional side cutters can't really get in there and do a precision job. So, in this case, both Pin 7 and Pin 8 got snipped. A better way to do the operation is to lift the pin rather than severe it. Take a soldering iron and copper braid and suck up most of the solder from the pin. Then while heating the pin, carefully pry it away from the SMD pad. At least that operation is reversible.

In both PCBs, there is a very clearly exposed trace that leads from Pin 7 to a large ground plane. It is very easy to get in there with a utility knife or Xacto blade and slice through the trace right where it joins the ground plane. The operation is easy for the average DIYer with conventional tools and little experience. It's also reversible. Cutting a pin kills any ability to reverse the procedure. I stand by what I say.
Title: Re: LED lights
Post by: frankenduck on April 10, 2021, 09:43:47 PM: I wholeheartedly agree that trying to cut only Pin7 with a conventional tool that one might have in their toolbox (like diagonal cutters) would be extremely difficult. For the later black cased relays with the smaller chip, as described on my web page, I just insert the tip of an ordinary push pin behind Pin 7 to break it away and bend it up. Works great and only takes a few seconds. I stand by my empirical results.

BMW Special Tool 07 11 9 908 666:
(https://i.imgur.com/CdGmsjj.jpg)

(http://www.kbikeparts.com/classickbikes.com/ckb.tech/0.ckb.tech.files/ledoemflrelay/23.Flasher.Relay.Black.Pin7.JPG)
Title: Re: LED lights
Post by: frankenduck on April 10, 2021, 10:46:36 PM: I'm sure you already know this but for others reading this here's what chip pins generally look like for the earlier green cased relays. Since the tip of the pin that goes through the circuit board is much thinner than the upper body of the pin it's pretty much always guaranteed to break off here:

(https://i.imgur.com/MR38zw8.jpg[center][/center])