PC XT 5160 Motherboard with patch wires

[wrljet]

I have this 5160 motherboard that just blew a tantalum capacitor, and noticed a few things about it while working on it.

64-256KB
Board p/n 6320155
Chips are mostly dated early/mid 1984

The tantalum capacitors are common 2-lead, not the more usual 3-lead I've seen before on IBM PC motherboards.
It does not appear to have been reworked previously.

It also differs in a few other ways from other 64-256KB motherboard pictures I've found online.

C64 is vertical on mine vs. horizontal in the picture here:

minuszerodegrees.net

R4 and R5 (near the 8255) are not populated. They are populated in some pictures online.

There are patch wires up at the top (of my attached picture).

Anything known or folklore about this version?

Thanks,
Bill

 

[modem7]

Anything known or folklore about this version?

There are quite a few variations of the motherboard PCB for the IBM 5150 and IBM 5160.
I myself, only get interested if a particular variation is known to cause a particular problem(s), a 5150 example described at [here].
But there may be someone out there interested in all of the PCB variations.

R4 and R5 (near the 8255) are not populated. They are populated in some pictures online.

Part of 'getting rid of the TD2 delay line'.
More information about that is in the 'Motherboard - DCLK signal' section of [here].

There are patch wires up at the top (of my attached picture).

Certainly not uncommon. I added some photos to [here], but gave up adding more after a while. We know that a particular set of patching to early 5160 motherboards was part of the move to 27256 EPROM's.

C64 is vertical on mine vs. horizontal in the picture here:

The tantalum capacitors are common 2-lead, not the more usual 3-lead I've seen before on IBM PC motherboards.
It does not appear to have been reworked previously.

At [here], I can see those two features on the 'IBM PC 5155 (5160) 64-256kB System Board #2'.
I should change a couple of pages on my web site.

 

[wrljet]

Thank you very much for all that info!

While pulling out the reset of the tantalums, I also noticed this one capacitor that was poorly installed.
There's no chance this was intentional, is it? For some inductive reason? It's C65 which is just another .047uF among a sea of others.

 

[modem7]

While pulling out the reset of the tantalums, I also noticed this one capacitor that was poorly installed.
There's no chance this was intentional, is it?

No.

It's C65 which is just another .047uF among a sea of others.

Yes, 0.047µF ceramic.

 

[wrljet]

There's about a dozen of those 0.047µF caps on the IBM mono board, all installed very sloppily like that.

 

[modem7]

There's about a dozen of those 0.047µF caps on the IBM mono board, all installed very sloppily like that.

Cheap and (unsupervised?) labour.

Long legs/leads only becomes an issue at very high frequencies, the inductance in the leg starting to have a significant negative effect. The higher the frequency, the greater the effect.

 

[wrljet]

These caps stick out far enough they could get bent over while handling/installing/removing the cards. And some of them can short to nearby pins on ICs. It's not very impressive workmanship.