Print

[fri0701]

I'm looking to repair the edge connectors that the CPU, I/O, and two memory boards plug into on the backplane (they're pretty corroded). Does anyone have a particular supplier or type that they've used and trust that they could send a link to?

Thanks!

[sigma7]

There aren't a lot of choices for manufacturers of card edge connectors, so you may be limited by what is in stock.

You do want to get a version that has gold plating on the contact/mating surfaces.

"AMP" (now "TE Connectivity") was one of the gold standards in the previous century and one would pay for that quality, but at this time I think any well known brand should be fine for this purpose.

There are lots of potential variations/options so look carefully to make sure the solder tails will fit and the plastic doesn't have any flanges that will interfere with other parts on the board or other oddities that make it fit a different design of board (eg. with a notch in it).

For CPU and I/O connectors...

Searching DigiKey today, there are 2 possible parts in stock with 120 contacts, dual readout, 0.100" spacing, vertical, solder tail, etc. ~$13 each. Both with mounting ears which you may need to cut off.

Mouser has 1 possible part (without ears) ~$19.

My choice today would be:
Jameco.com pn 2133536 is about $1 for a TE Connectivity 645235-8
https://www.jameco.com/z/645235-8-TE-Connectivity-Solder-Post-Edge-Connector-60-Positions-120-Contacts-2-54-mm_2133536.html

For Memory boards:

DigiKey has 9 potential parts; one is TE 5530843-7
https://www.digikey.com/en/products/detail/te-connectivity-amp-connectors/5530843-7/770546

Mouser has the same part
https://www.mouser.com/ProductDetail/TE-Connectivity/5530843-7?qs=CWN9I2qbSLtja0SlxvLT%2FQ%3D%3D

[Al Kossow]

sort of related..

how do people debug lisa cards?

have you built a edge card extender cable to be able to work on the cage outside the chassis, or just have a backplane, et. al. spare to work outside of the confines of the original case?

we just did some photos of the prototype Lisa that we have, and even back then they didn't have a cutout in the top of the sheet metal to put extender cards into the backplane.

[blusnowkitty]

sort of related..

how do people debug lisa cards?

have you built a edge card extender cable to be able to work on the cage outside the chassis, or just have a backplane, et. al. spare to work outside of the confines of the original case?

we just did some photos of the prototype Lisa that we have, and even back then they didn't have a cutout in the top of the sheet metal to put extender cards into the backplane.

Patrick and Tom both came up with expansion card extensions a while ago over on: https://lisalist2.com/index.php/topic,109.0.html

[stepleton]

Patrick and Tom both came up with expansion card extensions a while ago over on: https://lisalist2.com/index.php/topic,109.0.html

To be precise, I got 95% of the way there, but my expansion card wasn't quite the right shape. Life and other projects intervened before I tried to refine the shape. I'll get back to it someday, someday, someday... (echoes fade into the distance)

[fri0701]

Thanks for the suggestions! I'll definitely be picking some of these up.

While we're on the subject, recently I had an odd component failure in a 1.2A PSU - the transistor at CR21 "blew its top" and its case cracked in half (picture attached). I'd like to get a replacement... the schematics say this component is a "MPU131", which might be this: https://digitroncorp.com/Digitron/media/Files/Datasheets/MPU131-MPU133.pdf

I'm not sure where to find a replacement or appropriate substitute. Anyone have any ideas?

[blusnowkitty]

Thanks for the suggestions! I'll definitely be picking some of these up.

While we're on the subject, recently I had an odd component failure in a 1.2A PSU - the transistor at CR21 "blew its top" and its case cracked in half (picture attached). I'd like to get a replacement... the schematics say this component is a "MPU131", which might be this: https://digitroncorp.com/Digitron/media/Files/Datasheets/MPU131-MPU133.pdf

I'm not sure where to find a replacement or appropriate substitute. Anyone have any ideas?

I have a spare 1.2A supply in my parts box; the original is a Motorola MPU131. Looks like that datasheet you linked matches Motorola's original datasheet: https://datasheetspdf.com/pdf-file/658833/Motorola/MPU131/1

The original datasheet says the transistor can be "programmed" with two resistors in the circuit. I'd assume if you find a replacement and drop it in, it will behave just like the original part. Looks like this place has a large number of NOS Motorola parts: https://smallbear-electronics.mybigcommerce.com/transistor-mpu131-programmable-unijunction/

Probably would be wise to find out why the original part exploded, though.

[fri0701]

Thanks for the link!

Probably would be wise to find out why the original part exploded, though.

Yep, definitely true. It happened out of the blue, and it seems to have also damaged my CPU board. I've recapped this PSU and it's worked fine several times before, which makes it even more frustrating...

[blusnowkitty]

Yep, definitely true. It happened out of the blue, and it seems to have also damaged my CPU board. I've recapped this PSU and it's worked fine several times before, which makes it even more frustrating...

I can't quite make sense of the 1.2A schematic, but it appears CR21 ends up touching 5, 12, -12, and 5v Sense. It also appears to touch transformer T4 which may be on the AC side of the supply? I hope that transformer isn't shorted and letting line voltage through.

[sigma7]

If you are repairing a 1.2A PSU, this post from Patrick is required reading:

https://lisalist2.com/index.php/topic,290.msg2152.html#msg2152

[patrick]

While we're on the subject, recently I had an odd component failure in a 1.2A PSU - the transistor at CR21 "blew its top" and its case cracked in half (picture attached). I'd like to get a replacement... the schematics say this component is a "MPU131", which might be this: https://digitroncorp.com/Digitron/media/Files/Datasheets/MPU131-MPU133.pdf

This is a "programmable uni-junction transistor" (PUT). A long time obsolete device that behaves like a voltage controlled thyristor (a real thyristor or "silicon controlled rectifier" is current controlled). It has a high impedance until the gate voltage reaches a certain level and then it snaps to a low-impedance state.

PUTs were used for oscillators or, as here in this application, as comparators. Newer designs prefer to rely on the TL431A zener diode (which is not a direct replacement!).

I'm not sure where to find a replacement or appropriate substitute. Anyone have any ideas?

MPU131-MPU133 can be substituted by Motorola 2N6027 or 2N6028.

[fri0701]

I replaced one of my memory connectors today, and it looks like the replacement part will work well - thanks! I had a broken data line on my motherboard that I was able to patch, and now my memory problems look like they've gone away.

However, I have a new problem. The gray connector in the card bay (that connects to the drive, power switch, etc) has many pins that aren't contacting the edge of my motherboard properly. After removing the connector, I noticed several pins are very loose, and some have fallen out. Is this something I'll be able to fix, or is there a replacement that anyone's used in the past they can recommend?

[sigma7]

The gray connector in the card bay (that connects to the drive, power switch, etc) has many pins that aren't contacting the edge of my motherboard properly. After removing the connector, I noticed several pins are very loose, and some have fallen out. Is this something I'll be able to fix, or is there a replacement that anyone's used in the past they can recommend?

I think you are referring to the 60 contact card-edge connector that is bolted to the chassis and has a ribbon cable on the inside that splits off to the drive, power switch etc. (It is black on the Lisas that are in view to me at the moment, but I think your description narrows it down to that one)

It seems odd that some of the contacts are loose; a picture of those may be helpful in case a repair is straightforward...

At first look, this one is a bit problematic to source. I'd describe it as a 60 contact 0.1" pitch card-edge IDC ribbon cable connector with mounting flanges.

3M made this as part #s 3666-0000 and 3666-0002 but they are no longer available (you may find some NOS somewhere).

Panduit has part number varieties similar to 055-060-455x  where x is F or S for mounting flanges (no flange if blank), but the sites I've checked don't carry it.

This might be a usable part:
"(CPC) 499559-7"  near the bottom of the page at https://www.surplussales.com/ComputerAccess/con_edge.html

Alternate ideas:

Similar parts are available without the mounting flanges. If you can determine the cause of the loose contacts, it may be possible to purchase a similar connector of the same brand and scavenge contacts from it to repair yours.

60 contact card edge connectors with flanges and wire-wrap tails are available. Using one of these with a common 60 contact IDC socket header plugged onto the wire-wrap tails should work ok. The wire-wrap tails have a row spacing of 0.2" so they would need to be bent a bit to fit the header with 0.1" spacing.

The same part without the mounting flanges might be usable by fabricating flanges and attaching them. I think this may be difficult to make strong enough but not impossible.

[fri0701]

I am referring to that connector, yes. I was noticing problems with my power switch not working, keyboard having issues, etc, and narrowed it down to that connector.

To be more specific, many of the metal pins in that connector have lost their "springiness". Some have fallen completely out of the connector body, and at the end of each of these pins, there's a blue mound of corrosion. Removing the plastic back of the connector (that crimps the ribbon cables in place) revealed more blue corrosion.

I think, unfortunately, that the battery damage in this Lisa was so severe that it damaged this connector too, and the pins I'm seeing that are falling out are actually broken off, having been eaten away . In retrospect, this connector being unreliable explains a lot of the intermittent issues I've had with testing various boards, so I'm at least happy to have found the culprit.

For the short term, I have a spare harness from another Lisa body that I can swap in, but eventually, I'd like to find a more permanent replacement. A quick and dirty "solution", of course, would be to use any 60 pin connector that fits and to solder some ribbon cables directly to it, but I'd like to avoid that route. That link you sent seems like it would work, so maybe I'll give that a shot - thanks!

[sigma7]

I think, unfortunately, that the battery damage in this Lisa was so severe that it damaged this connector too, and the pins I'm seeing that are falling out are actually broken off, having been eaten away

In that case, you might save the housing portions of the connector in case you need to resort to replacing the damaged contacts with new ones from a similar connector of the same brand (eg. you may be able to get the same style of connector in a different size or without flanges).

As well as checking all of the remaining connectors, also examine the wires connected to them (as corrosion will progress along the wire under the insulation) and trim back or replace as needed.

Good luck!