Help Identifying Component!

[kb0nly]

Trying to fix a couple more Makerbot Mightyboards and unfortunately these have dead regulators for the 5v rail.  On the RevG and RevH boards in the Rep2 and Rep2X its a tiny IC, i think its called a 8DFN but not sure, just going off parts i can find that are at least similar looking, but it would be more helpful if i can ID the little bugger.  I've been pulling regulators off donor boards that have other issues but i have ran out of regulators to salvage.

All the info i have on this part is this...

8 pin package with center exposed GND pad. Its a buck regulator, 24v input, 5v output, should be rated for around 2A. --- Edit: Checked current draw on a working board, its more like 250mA.

Top of the IC on all the ones i have under a magnifier shows this..

LCLV
341E

That's all the info i have on them as Makerbot doesn't share any info on their boards.  And after fixing about 30 of these darn things i have run out of spare parts and need to find a source for a replacement.

Google searching for the numbers on the IC have come up with absolutely nothing unfortunately.

[floobydust]

I show SMT marking code LCLV, LCLT, LTDTR, LTDTS as LT3502

[kb0nly]

BINGO!!  Or as Dave would say... WE GOT ONE!!!

I just wasn't finding that in searches.  Can you share how you crossed LCLV to the LT3502?  Would be most grateful!

Looked up LT3502 on Digi-Key and bam, third part i looked at matched the pinout i was just trying to reverse engineer and scribble down on paper when i compared to the datasheet.

THANK YOU!! 

Now i think i need to take a nap, too much time staring at this board through a scope.  I'm fixing most of these for schools and makerspaces that gave up on Makerbot helping.  They still sell a RevH board, but for the hefty price of $400+... Most just can't afford that.  So i have refurbished dozens of these boards.  Now that i know what that regulator is i can refurb another dozen and get them back into use, i have 8 from one school district on the shelf.

[coromonadalix]

Having this defective quantity, it must be an bad design implementation maybe overheating issues or current surges

Good luck.

The rev E board schematics are ont the web, but the rev G an H seem harder to find, and yes they dont have the same layout ??

found out this : Mightyboard Rev G and later are closed source since that is when MBI switched over (Rep 2 and 2X) from open source you wont find any files on this board.

[coromonadalix]

Found out this :  the Rev E  had many problems

https://coolate.com/blog/blog/2015/02/23/its-alive-makerbot-replicator-repaired/
http://www.akeric.com/blog/?p=2836

[floobydust]

my (((google))) fu is usually a search query 'smt marking code ABCD' or the marking code and function 'voltage regulator ABCD'. You're really looking for the marking code mention in a datasheet.
I wish semi manufacturers would have a dedicated list for their marking codes.

It's very easy to mix up zero and oh 0 vs O and L vs 1 so I experiment with that.

[kb0nly]

Its not really a bad design, its bad owners most of the time.  Usually its someone forcing the power plug into the board upside down and applying reverse polarity, pop goes the reg.  Or the other case is someone shorting out the 5v at one of the limit switches, this was a big problem on the Rep1 series, but the 2 and 2X it wasn't as bad of a problem though it can still happen.  The first mod i do on these printers is clip the 5v lead going to the limit switches, its not needed for function, it was merely there to light an LED on the limit switch board showing that the switch is tripped!  Dumb..

On the Rep1 the most common fault was that they had a linear regulator for the 5v, and they were running it at its borders on both the input voltage (24v) and its output current.  You could add all the thermal management you wanted to it, water cool the sucker, doesn't matter, it just wouldnt hold up.  I replace the 5v regulator with a switching regulator on the RevE boards and they run forever, and if there is a short the 5v regulator just shuts down with OCP and your fine, find the short, reboot, and print some more.

The RevG and RevH boards are nearly non-existent when it comes to documentation.  I have reverse engineered about 80% of these boards, so i can fix the most common faults or troubleshoot them.  I have pages of DaveCAD on these... LOL

[kb0nly]

Found out this :  the Rev E  had many problems

https://coolate.com/blog/blog/2015/02/23/its-alive-makerbot-replicator-repaired/
http://www.akeric.com/blog/?p=2836

Actually the biggest fault on the RevE was just the power regulation.  Besides that they are fine.  The later clones of these boards made by FlashForge, Geeetech, Wanhao, CTC, they all went to a switching regulator for the 5v rail, that solved 99% of the issues.

On an original Rep1 RevE board you really only need to replace the 5v linear regulator with a switching regulator, i like to use a Murata Power part, OKI-78SR-5/1.5-W36-C‎ on a small circuit board i designed and built a case for.  The board includes poly fuses just in case if SHTF, but for the most part they have really good OCP and OVP, and just shut down if anything goes wrong.

The other problem on the RevE board was that they powered the 3.3v regulator from the 24v supply and it was just too much input voltage for them, so they modded their boards shortly after and cut a trace and jumpered the 5v output to the 3.3v input, which made that regulator behave, but put even more load on the 5v regulator, and it killed a lot of boards.  The worst part is the regulator would fail and short 24v to its output, frying every IC on the board.  I have rebuilt a lot of popped boards, its time consuming but cheaper then new boards. 

This is not to say that the RevG and RevH boards don't have their faults.  Their biggest fault is their tiny 150mA rated FET's for the cooling fans, get a fan that starts to gum up or stop one on accident and it pops the FET, i fixed that by putting on 3A rated FET's for the fans.  They do pop a Heater FET now and then, but usually only due to a dead short on the heater, and those FET's are a few minutes job to replace so its not overly terrible.

All in all, i much prefer repairing the RevG and RevH boards, generally its a couple small jobs on them and out the door.  When someone brings me a dead RevE board its usually a complete overhaul to get them working again because they had a 5v regulator blow.  I have three Rep1 printers, the oldest is over 6k hours on the clock, but i had modded everything on it when i got it, around 150 hours when i bought it used.  Its been solid ever since.  The other two were rebuilds i bought as dead printers, blown RevE boards, rebuilt them and they have 2-4k on them now as well.  My latest printer is a Rep2X that was also a dead printer but in excellent shape other then a blown board.  Quick repair on that and cleaning and it was running just fine, i think that one is nearing 1000 hours now.

[kb0nly]

my (((google))) fu is usually a search query 'smt marking code ABCD' or the marking code and function 'voltage regulator ABCD'. You're really looking for the marking code mention in a datasheet.
I wish semi manufacturers would have a dedicated list for their marking codes.

It's very easy to mix up zero and oh 0 vs O and L vs 1 so I experiment with that.

Apparently my Google Fu was off, i just wasn't getting any results on it.  But now that i checked out the LT3502 i see LCLV in the datasheet on them.  Ordered some from Digi-Key so i will solder on the first one in a couple days!