repair help with oscillator - Page 1
Forum section: electronics / repair

author: matura713
author_rank: Regular Contributor
timestamp: April 27, 2018, 09:56:27 pm
content: Hello All,one of my devices failed. So, I opened it and on the board near the chip that doesn't respond anymore the visual inspection shows something very strange - it's like one of the 4 pins of the crystal oscillator is completely corroded - check the attached picture I made.Have you seen such thing - I mean what can cause such corrosion (the air where i live is very dry and I've never spilled anything on the board, the rest of the board is indeed in excellent condition - like it has just left the factory)? Does such oscillator can leak something to cause corrosion like on the picture?Any advice how to proceed? I am not sure that's the fault, but it looks very suspicious and it's on the right place on the PCB, in the region where there is fault. I don't have such part to replace it otherwise I would already have done it.thanks!BTW, the part in question is "DMX-26S" - I am attaching PDF datasheet and picture of how it's supposed to look when it's new.

author: SMdude
author_rank: Frequent Contributor
timestamp: April 27, 2018, 11:22:14 pm
content: Well, if pin 4 is no longer connected/ missing that will stop your device from working.Is there anything left of pin 4? If there is a little stub left, you can clean this up and solder a small wire to it to get you going again.But first you will need to remove the oscillator and clean the board up and possibly the bottom of the oscillator too.It sure is a weird dot, I wonder if it is smd glue? When you clean it up I'm sure you'll figure it out!

author: matura713
author_rank: Regular Contributor
timestamp: April 27, 2018, 11:36:47 pm
content: Quote from: SMdude on April 27, 2018, 11:22:14 pmthank your for the idea, tomorrow i will clean the pcb (i need to clean that corrosion anyway) and try to rebuild the pin as per your suggestion.Quote from: SMdude on April 27, 2018, 11:22:14 pmas far as i can tell it's nothing like glue, looking it under magnifying glass it looks exactly like rusty metal, that's why i am wondering what can cause such really heavy corrosion and only on that specific place on the pcb. no doubt, very weird, i hope that's the root cause of the fault.

author: Ian.M
author_rank: Super Contributor
timestamp: April 28, 2018, 12:10:04 am
content: That's the sort of stuff that happens if there is a manufacturing process failure and board cleaning after soldering fails to remove *ALL* traces of a water washable flux from *ALL* joints and vias.

author: matura713
author_rank: Regular Contributor
timestamp: April 28, 2018, 12:20:54 am
content: Quote from: Ian.M on April 28, 2018, 12:10:04 amthat makes a lot of sense in case water washable flux is capable to do such heavy corrosion for only couple of years, because there is very tiny space between the plastic package and the pins of the oscilator, where flux can hide from really heavy cleaning.

author: Ian.M
author_rank: Super Contributor
timestamp: April 28, 2018, 12:40:52 am
content: Yes, which is why anyone who advocates anything except Rosin or synthetic Rosin or reputable brands of no-clean flux for manual rework, repair or prototyping has roos loose in their top paddock. My grandfather knew nearly a century ago that 'killed spirits' (acid zinc chloride - probably the first water washable flux) was unsuitable for electrical work but every new generation seems to make the same mistakes and in today's throwaway society there is little concern for product life and total life cycle environmental impact, as long as the production line can claim to be 'Green', 99% of units survive till the warranty runs out, and the eWaste can be made someone else's problem.If you can get them off the record, most MBAs in the industry will tell you that excessively high reliability is a BAD THING as it increases the second hand market reducing new sales, and increases resistance to sales of highly profitable extended warranties.