Friday, November 7, 2014

[Random Teardowns] REX-C100 PID Temperature Controller


Device: REX-C100 PID Temperature Controller  
Origin: eBay / China
Reason for teardown: DOA
Impressions: Not impressed to say the least. A mains trace near the connector (which has spring-contacts to horrid quality tin-plated contact pads on the board) blew out on first power-up. Guessing the trace was damaged from the get-go. Overall mediocre quality.




The thing is a lot smaller than what I imagined















 Made in Japan. Sure it was.

















 Power supply and main board














 Display board















 Some closeups

PS(A): Definitely don't go anywhere near the ratings of the relay unless you solder wires directly to the board.



It is what it is

Wednesday, November 5, 2014

[Quick Tip] Determining a Type K Thermocouple's Polarity

Say you took apart a type K thermocouple connector and don't remember which wire was connected to which terminal.


Here's a simple test to figure out the polarity: The negative wire is attracted to a magnet


Neodymium sphere magnet sticks to negative wire



And in case your connectors aren't marked: The wider pin is the negative.

Monday, November 3, 2014

Netbook hinge repair

What happens when you buy a netbook on auction for a friend, advertised as used in great condition with minimal wear and then the scammy seller sends you a machine that had it's hinge support posts broken off and what's worse: destroyed by a less than useful kludge? Well, if you're like me then after the negotiations have gone nowhere and the seller got the well deserved negative feedback (won't go there) you start thinking of ways to salvage the situation.

Here's the horror show:





You can't see it but basically someone tried soldering the metal threaded inserts into the plastic and once they were either satisfied with their "work" (the thing and beads of solder were rolling around inside the case when I got it..) or they realized the futility of their actions they then proceeded to drown everything in super-glue.

Turns out I should've done my research because the hinge supports were notoriously bad on this model and a large percentage of them that I've seen advertised since have had the same issue (minus the butchery of course)
The machine itself is some off-brand cheapy so got what I deserved and paid for, I guess..


The support posts were beyond hope so after racking my brain for a little while I came up with a following solution:

  • Cleaned up everything and filed off all the broken and melted parts until the stubs were level.
  • Drilled and countersunk holes from the top of the case where the posts were (or at least that was the plan but plastic just grips and pulls the drill bit so they both went a bit too deep, eh..)
  • Added long screws through the countersunk holes and spacers from a plastic tube on the inside (as a prosthetic to replace the broken sections of the support posts)





So now I could tighten the case together by using a nut where the screw went originally.

I also cleaned up the hinges (which were really seized up with grime and some leaked super glue) using dental floss and a tiny amount of mineral oil which worked really surprisingly well.

Did this quite a while ago and the machine (and hinges) have been in constant, daily use for the past 5 months at least. So far they're holding up great.

As an added bonus, the same person who botched up the case also turned out to have replaced the CMOS battery at some point by ripping the spot-welded tabs off the original and and loosely duct-taping them to a new one...


After all that the machine still has some sort of issue that I couldn't figure out but I'm sort of guessing that that's BGA-related so I'm not going to bother with it. It hard-locks under heavy load when cold booted (literally.. once it has warmed up the issue can't be reproduced. *shrug*)

Wednesday, October 29, 2014

Industrial Mini PC Quick Fix

Whew,  It's been an interesting year.
I am still alive just haven't been doing many things that are a good fit for an entry on this blog.

Here's a quick project from a few months ago.

I wanted a PC that a, wouldn't take up much space b, I wouldn't really care about breaking and c, had an LPT port for left-over DIY interfaces with enough processing power to run their associated tools if I needed them. 
A compact old-school hardware hacking PC if you wish.

I ended up buying 3 of these industrial mini pcs for somewhere around $20 if memory serves.
2 wouldn't boot, one was fine.




They had a FabiaTech FB2530 motherboard with a Geode CPU running at 266Mhz, dual ethernet, dual serial (which are pretty useful too), lpt, usb. Fits an IDE laptop HDD or a CompactFlash card for storage.








The issue with the 2 that wouldn't boot ended up being bulging capacitors in the power supply board.



They both started working fine after replacement.

Sold the ones I didn't need so I got to keep one for free. I've used it for a few projects since though it's mostly just been sitting on my desk for the past 6 months.

On the bright side it's really small and isn't much of an eyesore.