(Topic ID: 194751)
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1-phase-all holes one by one cleaned with cutter knife very carefully.Checked every trace and all of them are OK.
2-phase-reflow all holes.
3-phase-made this beautiful holes.
This was the hardest work.
Next it to replace all elements again near the corrosion area,upper left corner and some of 2n6427 transistors because they are corroded too and the elements around Timer 555.
Looking good!
Be sure to wipe off your camera lens--it's filthy, and that's why you're getting blurry photos.
Quoted from arakissun:I made the photos with my phone.
It's probably covered in grime from being in your pocket. I normally wipe off the lens every time I take out my phone to take photos. Otherwise, you end up with blurry photos like this.
Quoted from arakissun:I can see only blank IC from Chine.Is it possible to be programming?
I don't quite understand what you're asking. Are you looking for EPROMs too?
These.When I asked the seller he told me that they are blank IC.
I know or if I can remember rught that they are or blank or programmed for direct use.
Quoted from arakissun:PIA 6821P
http://www.ebay.co.uk/itm/10PCS-IC-MC6821-MC6821P-MOTOROLA-DIP40-NEW-/191908287574?hash=item2caea01456:g:GEcAAOSwgY9Xciki
These.When I asked the seller he told me that they are blank IC.
I know or if I can remember rught that they are or blank or programmed for direct use.
?
Those are the peripheral Interface ICs and are not chips that would need to be (nor can be) programmed.
To clarify, if I remember correctly, the PIA "technically" does get "programmed", but it is done by the MPU when the system boots up...
Not a type of program you have to do like you would for an eprom or anything.
Rochester, NY
Quoted from pacmanretro:To clarify, if I remember correctly, the PIA "technically" does get "programmed", but it is done by the MPU when the system boots up...
Not a type of program you have to do like you would for an eprom or anything.
Yes. Not programmed so much as configured.
Quoted from pacmanretro:To clarify, if I remember correctly, the PIA "technically" does get "programmed", but it is done by the MPU when the system boots up...
Not a type of program you have to do like you would for an eprom or anything.
Quoted from zacaj:Yes. Not programmed so much as configured.
They are sent instructions just like any other logic chip--not programmed or configured. These chips are plug & play.
Quoted from arakissun:What are all these "B" elements?
"B" indicates a faster speed. 6821 is 1MHz, while 68B21 is 2MHz.
Quoted from zaza:Any small capacitor 47pF/50V will work but if I'm correct, this is the circuit for the optos input at 1J9 ....which isn't used on your board.
The inputs of IC 30+39 are pulled HIGH by SR14 so that will keep them stable.
Zaza, I honestly don't know the answer, but just asking this question - if those caps are not used, why were they on his board in first pics?
Just curious.
Don't know, maybe it was a consideration to keep the circuit working and only cut cost on the header 1J9.
simple version of SW8 on J9 + J10.
WITH capacitor C48 the circuit is fully functional.
WITHOUT C48 and header 1J9, U39-13 is (always) +5Volt
But I should pass this question to the designers of this board as they made this decision 
2 months later
Finally PIAs arrived before several days.Put them.Run the board and everything works.
I'm very happy and the customer too.And he paid me good too.
This was my biggest corrosion project.Usually I don't like this type of fix but because in my country these boards cannot be found anywhere and usually the customers don't want to pay worldwide packages I need to fix them.
Very happy to hear you got it going! And thank you for taking the time to follow up on this thread; it is always nice when people let others know how it went.
If customer wants batteries to stay on the board (after all this happened to it once already), I would certainly politely suggest to them that they use high quality batteries, change them regularly, and even just visually check on them once in a while.
Again, congratulations on the repair!
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