Model A 5150 motherboard refurbishment #2

[pkhoury]

Just need some assistance for an otherwise working board that I was working on, to remove corroded memory sockets and slot #2 on the ISA bus. Another friend advised I should remove these sockets, as they had remnants from a RTC battery that leaked before I got the board.
Problem #1:

• What is the capacitance of the memory ceramic caps? From what I read, it says K5M 473, which I'm guessing is 43pF? Anything else I need to pay attention to?

Problem #2:

• I pulled a few traces from the top of the motherboard that connect ISA sockets 1 and 2. Can I get away with soldering some rework wires to bridge those lines together on the underside?
• Getting out the ISA socket was a real pain in the ass.

 

[modem7]

What is the capacitance of the memory ceramic caps? From what I read, it says K5M 473, which I'm guessing is 43pF? Anything else I need to pay attention to?

See the 'Capacitor Tolerance Letter Codes Table' section of [here], where '473' is actually given as an example.

No polarity.

Voltage wise, some are on the +5V line, some are on the -5V line, and some are on the +12V line. The technical reference for the early IBM 5150 indicates "15VWDC", which is 15V DC working voltage. There should be no issue is using a higher rated voltage.

I pulled a few traces from the top of the motherboard that connect ISA sockets 1 and 2. Can I get away with soldering some rework wires to bridge those lines together on the underside?

I cannot see why not.
I did it at [here].

 

[pkhoury]

I cannot see why not.
I did it at [here].

LOL; yes you did! That gives me hope, because I was hoping to keep this board as a spare.
I need to grab a photo, but I bought an otherwise worthless XT clone at VCFSW JUST for the power supply - early black 5150 supply with nuts on top and IBM part number (which would get paired with this board).

Another question relating to a 5160 (but while it's on my mind); and yes, I did read your site and other comments on other threads. Just to be clear - I should be fine using 2 legged tantalums on a motherboard with 3 legged, so long as I do polarity correctly, right? As I understand it, negative, positive, negative, right? On the board in this thread, I already recapped it just to be on the safe side.

 

[jafir]

I wonder if that chipquik low melt solder usually used for SMD component removal would be useful for removing parts from these boards too.

 

[modem7]

Another question relating to a 5160 (but while it's on my mind); and yes, I did read your site and other comments on other threads. Just to be clear - I should be fine using 2 legged tantalums on a motherboard with 3 legged, so long as I do polarity correctly, right?

Correct, and on an IBM 5160, done per option 2 at [here].

Technical: One intended use of three-legged capacitors is shown at [here]. In the IBM 51xx series, IBM have not wired things that way.

As I understand it, negative, positive, negative, right?

Yes, for the IBM 5160, the hole pattern in the PCB is negative-positive-negative, irrespective of whether the capacitor is filtering a positive or negative voltage.

On the board in this thread, I already recapped it just to be on the safe side.

That is an IBM 5150 motherboard. Things can be different:

5150 motherboard of type 16KB-64KB: Per [here], only uses 2-legged capacitors.
5150 motherboard of type 64KB-256KB: Same situation as the IBM 5160.