The crustiest COB I have ever seen - Page 1
Forum section: electronics / general

author: nkeck72
author_rank: Contributor
timestamp: January 11, 2016, 11:21:00 pm
content: I recently took apart a Chinese piano keyboard, just to see what was inside (I seem to have a newfound addiction of teardowns of Chinese stuff...).As per usual, there was a blob inside controlling everything but it looks like almost the most crusty component I have seen since the TRS-80 monitor Dave took apart...It just sends shivers down my spine to see this. They also mounted the COB on a seperate board and soldered it to the *inside* of the main board. The top looks fine but looking at the bottom killed any optimism I had left.Pics are attached. I guess it is a positive that they used NE5532s from TI.Sent from my SGH-T399 using Tapatalk

author: nkeck72
author_rank: Contributor
timestamp: January 11, 2016, 11:25:06 pm
content: More pics of the whole thingHere you can see the COB board mounted in the main oneSent from my SGH-T399 using Tapatalk

author: Tomorokoshi
author_rank: Super Contributor
timestamp: January 11, 2016, 11:55:07 pm
content: All right... who's the joker that switched the potting compound with industrial waste again?

author: Macbeth
author_rank: Super Contributor
timestamp: January 11, 2016, 11:58:19 pm
content: WTF? Is it suffering from some kind of yeast infection? Or do they just jizz on them during assembly then preserve it with a blast of the hot air?

author: nkeck72
author_rank: Contributor
timestamp: January 12, 2016, 12:09:56 am
content: What I thought was interesting was how they mounted the seperate COB board. Never seen that beforeIt does look like a yeast infection, doesn't it?Sent from my SGH-T399 using Tapatalk

author: nkeck72
author_rank: Contributor
timestamp: January 12, 2016, 12:12:50 am
content: Even better were the speakers. Looks like they've seen better daysSent from my SGH-T399 using Tapatalk

author: nkeck72
author_rank: Contributor
timestamp: January 12, 2016, 12:17:51 am
content: The whole unit is apart, and it only had about 200 screws holding it togetherSent from my SGH-T399 using Tapatalk

author: djQUAN
author_rank: Frequent Contributor
timestamp: January 12, 2016, 12:44:12 am
content: Looks like improperly cleaned flux to me. Try using cotton swab and IPA or flux cleaner. It should come off easy.

author: nkeck72
author_rank: Contributor
timestamp: January 12, 2016, 12:45:38 am
content: Will try. I thought somehow the COB was forming some kind of icky poisonous goo.Sent from my SGH-T399 using Tapatalk

author: Macbeth
author_rank: Super Contributor
timestamp: January 12, 2016, 01:03:01 am
content: I imagine the original PCB's had a through hole DIP processor and all the boards had been produced, then some genius bean counter found out about COB's and got brownie points, only leaving it to the workers to have to dremel out the area of the old DIP, scrape the soldermask to make something to bridge onto, then insert these new custom PCB's with COB and no doubt have to file bits away just to fit then splurge that shitty solder over the crevasse just to join it to the original PCB. Thoroughly disgusted that they had to work overtime x 10 and not get paid for it they spat gobs of phlegm on the COB hybrid spaz board. The company eventually went under due to this pointy headed genius managers innovation.

author: nkeck72
author_rank: Contributor
timestamp: January 12, 2016, 01:38:37 am
content: Made in China! Gotta love 'em.Sent from my SGH-T399 using Tapatalk

author: vk6zgo
author_rank: Super Contributor
timestamp: January 12, 2016, 01:57:02 am
content: Quote from: djQUAN on January 12, 2016, 12:44:12 amYeah,that's what it looked like to me!If you use ordinary facial tissues,rather than,say,"Kimwipes",you sometimes get tufts of paper fluff stuck to any protrusion.Cotton swabs & lots of IPA will soon tidy that up.

author: amyk
author_rank: Super Contributor
timestamp: January 12, 2016, 04:27:35 am
content: Quote from: Macbeth on January 12, 2016, 01:03:01 amIt was never designed for a DIP - look at the traces on the sides. The board was designed this way in order to use cheaper low-density process for the bulk of it and a more expensive, high-density fab for the COB module (which may have come from a different manufacturer.)The "64C" designation on the COB board, along with the 14.318MHz crystal (interesting choice of frequency...) leads us to find what the COB is:a Generalplus GPFA64C, a 6502-based MCU with 64K of mask ROM and 224 bytes of RAM. Some very juicy info on that MCU family can be foundhere.

author: nkeck72
author_rank: Contributor
timestamp: January 12, 2016, 12:10:27 pm
content: Hmm, I've done some 6502 assembly in the past...Wonder if I can sneak some of my programming in there, make it sound a little better

author: PA0PBZ
author_rank: Super Contributor
timestamp: January 12, 2016, 12:17:52 pm
content: Quote from: nkeck72 on January 12, 2016, 12:10:27 pmQuoteGood luck with that...

author: nkeck72
author_rank: Contributor
timestamp: January 12, 2016, 12:22:49 pm
content: Doh!I didn't see that

author: Lukas
author_rank: Frequent Contributor
timestamp: January 12, 2016, 01:13:15 pm
content: I've seen many cheap chinese products use PCBs of similar style where some tracks are expanded to fill empty areas. Anyone why they're doing it? Having to etch less copper off or are they all using the same CAD tool?

author: free_electron
author_rank: Super Contributor
timestamp: January 12, 2016, 03:35:44 pm
content: flux remnants that have reacted with humidity. possibly water soluble flux.kinda neat how they made that board. the chip carrier punches out : they install the chip , globtop it then stick it back in the opening where it came from. and solder it by hand.(hence the flux remnants)globtops cant go through wave soldering : they popcorn.

author: Macbeth
author_rank: Super Contributor
timestamp: January 12, 2016, 07:08:24 pm
content: Quote from: amyk on January 12, 2016, 04:27:35 amIgnore my prior idiocy, but great detective work! I'm surprised the 6502 is still used even if in a COB form.

author: nkeck72
author_rank: Contributor
timestamp: January 12, 2016, 08:52:20 pm
content: Hmm, I have never seen a COB gone popcorn.I personally have used the 6502 in a couple beginner designs, not in a production one though.