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Author Topic: Edge Connector for the IO Board  (Read 340 times)

pintoguy

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Edge Connector for the IO Board
« on: April 19, 2022, 04:49:45 pm »

I'm working on repairing a corroded Lisa 2/5. The IO Card edge connector on the motherboard was so corroded that after cleaning, a few pins got loose and broke off (see bottom pic). I bought a new 2x60 pin connector on eBay, but upon trying to remove the old connector, I realized how extensive of a job that is and thought I could just remove the right-most 8 pins (2x4 - see top pic). I used a hot blade, and it was quite a bit easier than I thought ( I still messed up a couple of traces removing the soldered pins  :( ). I could then simply do the same with a cheap 36 pin connector and abut the new 8 pin bit to the existing space. Has anyone tried this ? Would anyone think it's a bad idea ? If it IS a bad idea, how's the best method to remove the 120 pin connector ?
« Last Edit: April 23, 2022, 08:21:44 pm by pintoguy »
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blusnowkitty

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Re: Edge Connector for the IO Board
« Reply #1 on: April 20, 2022, 10:24:43 am »

Removing connectors, either be patient with an iron, wick, and lots of flux, or pick up a desoldering gun. Hakko makes a nice one if you're willing to spend the money, and I've heard decent things about the generic Chinese ZD-915.

I don't see any physical reason why chopping two connectors apart wouldn't work, but electrically I'd be concerned with the two pieces being physically different in some way - either one or the other is taller or shorter than the other, or there's a slight angle one way on one connector and an angle the other way which could lead to a bad electrical connection.

You would probably want to remove the connector completely anyway. I have seen a couple Lisa backplanes have broken traces that were invisible as the break happened directly under the connector body.
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AlexTheCat123

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Re: Edge Connector for the IO Board
« Reply #2 on: April 20, 2022, 01:19:18 pm »

As long as the new connector has the same dimensions as the old one (with the exception of it being shorter and having fewer pins), I don't see a problem with this. But it would obviously look better (and maybe be more reliable) if the entire connector could be replaced at once.

It can definitely be done with solder wick, but it's not a fun process! When I first got my Lisa, I had to desolder all four connectors this way and it took around 10 hours since the corrosion on the solder joints made things even harder than they would be otherwise. I would highly recommend getting one of the Hakko desoldering guns; it's a bit expensive, but super useful and it can remove one of those connectors in 5 to 10 minutes.

But if you don't care about aesthetics or just want a temporary solution, splicing in part of another connector should work perfectly fine!
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pintoguy

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Re: Edge Connector for the IO Board
« Reply #3 on: April 21, 2022, 10:58:00 am »

OK thanks. I ordered both the full 120-pin one, and a small one. The small one is black, so it matches the color of the existing connector. The full one is green, so it will contrast with the CPU connector that's black, so perhaps I'll opt for the cut-out solution. I'll report after I get the parts.

And thanks for the tip on the desoldering unit. I might do the investment....
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pintoguy

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Re: Edge Connector for the IO Board
« Reply #4 on: April 23, 2022, 08:18:10 pm »

Update: I'm fairly happy with this repair. The color, height, and width match, and once the IO board is in place, it's hard to see the junction. I repaired all the traces, and the system looks like it's booting up: the on/off button is now dark and lights up upon switching. I can hear the speaker make some noise after 5 secs or so, then a series of beeps after ~15 secs: hi hi lo (no keyboard/mouse: expected) and hi hi hi (no startup device: also expected). But.... no video. I'm not too worried about this one, but who knows...
« Last Edit: April 23, 2022, 08:22:38 pm by pintoguy »
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blusnowkitty

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Re: Edge Connector for the IO Board
« Reply #5 on: April 23, 2022, 11:20:47 pm »

Whack an old CRT TV/monitor with composite in on the Video Out port, or hook up a scope to the port and see if you have any signal at all - the video port is the same signal that gets fed into the Lisa's internal analog board. Video output is also on Pin 115 of the CPU board.

http://bitsavers.org/pdf/apple/lisa/hardware/lisa-motherboard-enhanced.pdf
https://lisa.sunder.net/cgi-bin/bookview2.cgi?zoom=0?image=0?book=6
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pintoguy

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Re: Edge Connector for the IO Board
« Reply #6 on: April 24, 2022, 11:10:33 am »

Thanks @blusnowkitty. I had read these posts, and this was going to be my next move.
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pintoguy

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Re: Edge Connector for the IO Board
« Reply #7 on: April 25, 2022, 12:34:02 pm »

mmm, I spoke too soon. The problem seems more complicated than I thought.

1) I checked the composite video signal, and it looks OK, and similar to what I get on a working Lisa (see pic)
2) I swapped the PS with my working Lisa, with same results
3) I swapped the Video board with my working Lisa, with same results
4) The CRT glows red

I was thinking of swapping the whole card cage with my working Lisa 2/10, but this one is a 2/5 with the parallel port. And the 2/10 cage doesn't seem to fit very well. Would they be compatible ? Should I force the 2/10 cage in ?
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blusnowkitty

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Re: Edge Connector for the IO Board
« Reply #8 on: April 25, 2022, 01:39:20 pm »

Have you tried twiddling the knobs on the affected Lisa's analog board? I know when I was trying to get my 2/5 up and running on its original battery damaged I/O board, the video signal was so overdriven the screen was mostly white with black smears here and there.

You could also have a broken component on your analog board. Mine apparently had been used so much that a plastic insulating tube on one of the coils broke apart. Fortunately there wasn't any electrical damage.
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patrick

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Re: Edge Connector for the IO Board
« Reply #9 on: April 25, 2022, 01:51:31 pm »

I was thinking of swapping the whole card cage with my working Lisa 2/10, but this one is a 2/5 with the parallel port. And the 2/10 cage doesn't seem to fit very well. Would they be compatible ?

This will work as long as you do not connect any floppy or hard drives. The power harness is almost the same for the 2/5 and 2/10, but the drive harness is different.
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sigma7

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Re: Edge Connector for the IO Board
« Reply #10 on: April 25, 2022, 03:04:24 pm »

mmm, I spoke too soon. The problem seems more complicated than I thought.
U1 - 74LS132 on the motherboard is in the signal path for built-in video, so look around there, swap it out, suspect the socket, etc.

The video signals aren't associated with the I/O connector you worked on, and all of those discrete components in the area of Q1 & Q2 are for the external video only.
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pintoguy

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Re: Edge Connector for the IO Board
« Reply #11 on: April 25, 2022, 03:59:48 pm »

Have you tried twiddling the knobs on the affected Lisa's analog board? I know when I was trying to get my 2/5 up and running on its original battery damaged I/O board, the video signal was so overdriven the screen was mostly white with black smears here and there.

You could also have a broken component on your analog board. Mine apparently had been used so much that a plastic insulating tube on one of the coils broke apart. Fortunately there wasn't any electrical damage.

Is Analog board = Video board ? If it is, then yes, I fiddled with all the trimpots with no success. And I did put a spare, working video board in the 2-5, again a no-go

This will work as long as you do not connect any floppy or hard drives. The power harness is almost the same for the 2/5 and 2/10, but the drive harness is different.

OK thanks. The floppy drive needs work anyway, so I'll remove the drive cage and try.

U1 - 74LS132 on the motherboard is in the signal path for built-in video, so look around there, swap it out, suspect the socket, etc.

Great, thanks. I'll check

By the way, the video contrast latch circuitry is on the IO board. Could a faulty latch make the screen blank ?
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pintoguy

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Re: Edge Connector for the IO Board
« Reply #12 on: April 25, 2022, 06:19:57 pm »

Success !! I had both Hsync and Vsync traces corroded away, right near the connector J5 on the MoBo. They are actually very narrow there, and it doesn't take much oxidation to eat the copper up completely.

Now on to the floppy drive (all seized up) and the keyboard (foam pads need replacement).

Thanks, as always, to all the good people on this board or on 68kmla where I used to post. You guys are the best !

(Edit): Am I the only one having trouble with file attachment ? I've been trying all day. Sometimes I get the error message: "Your attachment has failed security checks and cannot be uploaded. Please consult the forum administrator". Sometimes it looks like it's working, but it is actually not uploading the pics.
« Last Edit: April 25, 2022, 09:05:07 pm by pintoguy »
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compu_85

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Re: Edge Connector for the IO Board
« Reply #13 on: April 29, 2022, 12:37:54 pm »

I've had some luck swapping individual pins on I/O board connectors. After desoldering and removing the subs, be sure all the old solder is removed. Then a new pin can be slipped in from the top.

This assumes there's no board damage / other grunge under the edge connector. If it looks green under the plastic, best bet is to remove the whole thing and clean under it.

-J
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pintoguy

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Re: Edge Connector for the IO Board
« Reply #14 on: May 03, 2022, 01:52:21 pm »

Good to know. Thanks
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