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I broke my IBM Async Card jumper block...

B

bvcderrttyyhjjjk

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Jan 30, 2020
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Hello,

came back for help again, you guys always save me when I think I'm screwed.
So, long story short, I bought an Async Communication Card for my IBM 5155, because it didn't have a serial port and I wanted one to do some experimenting.
I was about to install it, did some reading and figured I needed to reverse the "shunt block" at the top right of the card to make it the primary serial adapter.
This thing basically goes into an 8 pin IC socket but seems to be just jumpering two of the four pins across.

I go to pull it out and one of the pins snaps right off. Maybe I should have been gentler, maybe the previous owner damaged it already, maybe both.
Anyway, I now need a replacement, but almost an hour of googling has not produced anything useful. I can't find a part like that anywhere.

I just wanted to check if anyone here ever dealt with this issue or knows where to find a component like that.

Thank you!
 
Yes! That looks almost exactly like it, I think it should work. Thank you!

I couldn't figure out the exact term for it and I couldn't find anything like it.
As always I am very impressed with the speed with which this community can find the exact solution to the exact obscure problem I am having. You guys are insane. LOL

Thank you so much, you saved my day once again.
 
No problem! Helps to work in a field that requires regularly sourcing and purchasing stuff like that :) A lot of the terms are non-intuitive.
 
I have the same IBM Async card in my IBM5155, it is a good little card. Mine had a defective line receiver IC, its not a common type, a 75 series part and I didn't have one in my parts box. But I was able to effect a temporary repair by hijacking an unused gate in the package, so I wrote a little story about it:

http://worldphaco.com/uploads/LOST_IN_SPACE_REPAIR.pdf

I have had faulty line receiver/driver IC's in my other vintage computers as well. I think the inputs of these IC's are a little vulnerable to electrostatic discharges from long cables being plugged in, or perhaps in some cases one of the serial device's signal common is not at ground potential (not earthed) and the two devices are hot plugged and the discharge currents on the signal lines damage the IC's.
 
Yeah, drivers and receivers often get the worst of it if there's a failure in whatever they're connected to. Ground potential differences can also blow them up, even if everything on both ends is otherwise fine.
 
rittwage said:
Probably almost any 8 pin DIP switch will plug into the socket.
Click to expand...

I have replaced most of the DIP switches on my S-100 computer boards. I have had a lot less trouble with the ones in my IBM5155, mind you they are not quite as old. Probably one advantage of the type of hard wired link on the Async card is they would be very reliable.

DIP switch reliability has a lot to do with the internal design of the switch as to what happens in the long run. For those with contacts that touch, even gold plated, they can make unreliable connection as a film builds up on the gold surface over many years. For these with sliding contacts the friction breaks through this thin layer and they are self cleaning. Intermittent DIP switches can be a nightmare to find.

The type I use as replacements plug into an IC socket, so usually when I replace a DIP switch I fit a socket. The best quality ones I could find are made by Omron, like these, they are low profile and when plugged into an IC socket, the total height is practically identical to vintage DIP switches. Also, the pin geometry is perfect for the IC socket, sometimes other DIP switch types for pcb soldering, the pins are not exactly correct for socket insertion:

https://www.digikey.com.au/product-detail/en/omron-electronics-inc-emc-div/A6T-8104/SW1131-ND/307762
 
Yeah there's definitely a range of quality on DIP switches. I tend to only use CTS and Grayhill, usually Grayhill for sealed since they don't require tape for water washing. I haven't had many fail, but I did replace one just last week that had gone high resistance.

Pretty hard to get a programmable DIP shunt to fail though :)
 
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