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A Tale of Two Luggables (IBM 5155)

phonophan

Experienced Member
Joined
Nov 10, 2019
Messages
67
Location
New Jersey, USA
Greetings -

So, I drove an hour for a Facebook market posting showing an IBM 5155.

When I got there in person and powering it on... the floppy drives were not reading. He said, "oh... I have another one" ... so we powered that one on and the monitor was dead but I could hear the floppy drives reading... well, long story short, I made an offer for both (not knowing he had two) and left with both! :crazy: He said when he moved into the house, he and found them in the attic - and thought they were suitcases at first (both in their zippered carrying cases).

LUGGABLE 1
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The one that wasn't recognizing the floppy drives didn't have a screw holding the card in, so somehow it was loose. Pop it back in... all appears to be in good working condition... computer, screen and drives.

IMG_1524.jpg

IMG_1522.jpg

LUGGABLE 2
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The built in monitor is just dead... no flickering, no images, no signs of life whatsoever... but hooking up a TV shows the computer and drives are also in good working condition.

IMG_1526.jpg

IMG_1523.jpg

So, a few questions...

1) Are there any troubleshooting methods for the dead monitor? I'm definitely not qualified to go digging around in CRT guts.

2) Are there any quantifiable differences between the two motherboards and processors? (pictured above: one Intel branded CPU with white switch box and the other NEC branded CPU with blue switch box)?

3) Lastly, any advice overall is certainly welcome.

Thank you for your time and help!
 

modem7

Veteran Member
Joined
May 29, 2006
Messages
7,904
Location
Melbourne, Australia
2) Are there any quantifiable differences between the two motherboards and processors? (pictured above: one Intel branded CPU with white switch box and the other NEC branded CPU with blue switch box)?
No functional differences.
IBM used different part suppliers (e.g. price competition, no single line of supply).

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LUGGABLE 2
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The built in monitor is just dead... no flickering, no images, no signs of life whatsoever... but hooking up a TV shows the computer and drives are also in good working condition.

...

1) Are there any troubleshooting methods for the dead monitor? I'm definitely not qualified to go digging around in CRT guts.
- Verify, that like machine #1, the video cable from the CRT display unit is connected to connector P1 on the CGA card ([photo]).

- To identify a possible faulty CGA card, try swapping the CGA cards between the two machines.

- Per the photo at [here], the CRT display unit is powered by +12V from the power supply, via the dedicated connector of P12. Try re-seating that connector. And verify that +12V is present on it.
 

hackerb9

Experienced Member
Joined
Jul 14, 2015
Messages
74
Location
Earth, currently.
LUGGABLE 2
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The built in monitor is just dead... no flickering, no images, no signs of life whatsoever... but hooking up a TV shows the computer and drives are also in good working condition.

I know this sounds silly, but have you tried turning up the brightness knob next to the monitor?
 

phonophan

Experienced Member
Joined
Nov 10, 2019
Messages
67
Location
New Jersey, USA
This was beyond my repair ability... but was worked on by someone else.

First was testing for voltage issues, replaced a resistor and transistor to no avail.

Attach01(2).jpg

Replacing the horizontal output transistor did produce an image but the vsync was off.

Attach01(3).jpg

Replaced resistor capacitor to still no avail ... and unfortunately accidentally broke the tube during repair.

Can't believe a new old stock tube was found, but installed it and voi-la... working luggage.

Screenshot_20200501-205849_Video Player.jpg

Just thought i'd share!
 
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