amstradus wrote on 2025-10-13, 18:50:

(2) Any recommendations of how I might jimmy a new ground? I have basic soldering skills but no theoretical knowledge as far as these things go. I suppose the next step might be to open the case and look to where the chassis would normally be seated.

I wouldn't worry about the electrical aspect. Obviously, ISA cards need ground for operation, but they don't receive ground via the slot bracket, but from 3 contacts on the ISA bus. Those contacts are still working fine on your computer. You thus should focus on the mechanical aspect. For cards without external connectors, like your XT-IDE, I still wouldn't worry, but if your SoundBlaster card can be partly torn out of the ISA slot if someone trips over the speaker cable, this may cause a short circuit on the ISA bus. This is only a concern if the missing metal bracket is the main support for the mounting screws. If the mounting screws are sufficiently supported by the plastic case and do not rely on a metal thread, you should be fine wihtout the bracket.

yep, the metal bracket is made of the same thin metal which the mainboard shielding is made out of.
It won't offer any substantial structural benefits.

mkarcher wrote on 2025-10-13, 19:42:

amstradus wrote on 2025-10-13, 18:50:

(2) Any recommendations of how I might jimmy a new ground? I have basic soldering skills but no theoretical knowledge as far as these things go. I suppose the next step might be to open the case and look to where the chassis would normally be seated.

I wouldn't worry about the electrical aspect. Obviously, ISA cards need ground for operation, but they don't receive ground via the slot bracket, but from 3 contacts on the ISA bus. Those contacts are still working fine on your computer. You thus should focus on the mechanical aspect. For cards without external connectors, like your XT-IDE, I still wouldn't worry, but if your SoundBlaster card can be partly torn out of the ISA slot if someone trips over the speaker cable, this may cause a short circuit on the ISA bus. This is only a concern if the missing metal bracket is the main support for the mounting screws. If the mounting screws are sufficiently supported by the plastic case and do not rely on a metal thread, you should be fine wihtout the bracket.

Thanks! You're sure they receive ground via the contacts on the ISA bus?

I originally thought it was just a bracket for mounting the cards but when I looked on the parts diagram I saw this piece is labeled "Plate earth CPU". So if you're sure they are grounded via the bus themselves, maybe the bracket serves as a backup ground? Here is the page with the cabinet part names:

weedeewee wrote on 2025-10-13, 20:35:

yep, the metal bracket is made of the same thin metal which the mainboard shielding is made out of.
It won't offer any substantial structural benefits.

thanks for your reply. Refer to my last post. Without the bracket, the cards can wobble a bit from side to side, as the bracket provided a spacer underneath the screw heads. I can probably find some sort of spacer, but mainly concerned about the grounding aspect.

amstradus wrote on 2025-10-13, 20:41:

Thanks! You're sure they receive ground via the contacts on the ISA bus?

I originally thought it was just a bracket for mounting the cards but when I looked on the parts diagram I saw this piece is labeled "Plate earth CPU". So if you're sure they are grounded via the bus themselves, maybe the bracket serves as a backup ground? Here is the page with the cabinet part names:

Yes. I am confident that any sensibly designed card will receive ground for electronic operation from the ISA bus. The slot bracket itself may or may not be connected to the ISA ground.

The reason for all the extra grounding is not electronic functionality, but radiation shielding. In the 80s, electromagnetic compliance enforcement was quite hard towards computers, so a lot of shielding was built into computers to make regulators happy. A grounded plate is much more effective in blocking radiation than a metal plate that is not grounded. That's why all those metal parts are grounded.

I don't know whether electromagnetic compliance standards changed in the mean time, but at least enforment is way more lax in Europe and North America than it was in the 1980s, so likely no one cares about a missing ground bracket in that computer.

mkarcher wrote on 2025-10-13, 23:04:

Yes. I am confident that any sensibly designed card will receive ground for electronic operation from the ISA bus. The slot brac […]
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amstradus wrote on 2025-10-13, 20:41:

Thanks! You're sure they receive ground via the contacts on the ISA bus?

I originally thought it was just a bracket for mounting the cards but when I looked on the parts diagram I saw this piece is labeled "Plate earth CPU". So if you're sure they are grounded via the bus themselves, maybe the bracket serves as a backup ground? Here is the page with the cabinet part names:

Yes. I am confident that any sensibly designed card will receive ground for electronic operation from the ISA bus. The slot bracket itself may or may not be connected to the ISA ground.

The reason for all the extra grounding is not electronic functionality, but radiation shielding. In the 80s, electromagnetic compliance enforcement was quite hard towards computers, so a lot of shielding was built into computers to make regulators happy. A grounded plate is much more effective in blocking radiation than a metal plate that is not grounded. That's why all those metal parts are grounded.

I don't know whether electromagnetic compliance standards changed in the mean time, but at least enforment is way more lax in Europe and North America than it was in the 1980s, so likely no one cares about a missing ground bracket in that computer.

Great info, thank you. I wonder if this is the reason why my speaker I set up yesterday just to the right of my computer is picking up the Mexican radio so strongly. haha. I don't recall that happening before.

For spacers, paper grounding washers would probably do. Just stack them underneath, attach the screw, and hope for the best.

If you feel you absolutely must have a grounded plate there, you can probably fabricate the needed goodie out of copper cladding, then tin it in tinning solution. Original part was probably galvanized steel, but the metallic dissimilarity of the copper would be obviated by tinning it, and it would be nice and silvery shiny afterward.

You can make your own tinning solution using automotive grade muriatic acid, some tin based solder, and some silver polish (check the ingredients)

https://www.youtube.com/watch?v=Hsw3lOnHaas

This sheet of copper should be plenty large enough. It should be possible to reverse-derive a flat pattern based on measurements of the case, use a laser printer to print a reverse image of the flat pattern, then use a chemical solvent based transfer of the black toner to the copper sheeting using something like wintergreen oil. Once the pattern is on the copper, you just need to cut it on your transferred lines, then bend it at the marked areas. Once its cut and bent, clean it real good with more wintergreen oil then a degreaser, and then soak it in the tinning solution.

https://www.amazon.com/ZOFORTY-Attached-Jewel … /dp/B0DZFXPS5M/

video for wintergreen oil transfers.
https://www.youtube.com/watch?v=JFxEwSq-wPI

Be sure to use in a ventillated area. the oil will be overwhelmingly pungent.

Another solution one could use is acetone+alcohol.
https://www.youtube.com/watch?v=HBIxvwZ_0og

But as others have stated, the part is really not required for operation. This is just for cosmetic considerations of having it.

wierd_w wrote on 2025-10-14, 04:06:

For spacers, paper grounding washers would probably do. Just stack them underneath, attach the screw, and hope for the best. […]
Show full quote

For spacers, paper grounding washers would probably do. Just stack them underneath, attach the screw, and hope for the best.

If you feel you absolutely must have a grounded plate there, you can probably fabricate the needed goodie out of copper cladding, then tin it in tinning solution. Original part was probably galvanized steel, but the metallic dissimilarity of the copper would be obviated by tinning it, and it would be nice and silvery shiny afterward.

You can make your own tinning solution using automotive grade muriatic acid, some tin based solder, and some silver polish (check the ingredients)

https://www.youtube.com/watch?v=Hsw3lOnHaas

This sheet of copper should be plenty large enough. It should be possible to reverse-derive a flat pattern based on measurements of the case, use a laser printer to print a reverse image of the flat pattern, then use a chemical solvent based transfer of the black toner to the copper sheeting using something like wintergreen oil. Once the pattern is on the copper, you just need to cut it on your transferred lines, then bend it at the marked areas. Once its cut and bent, clean it real good with more wintergreen oil then a degreaser, and then soak it in the tinning solution.

https://www.amazon.com/ZOFORTY-Attached-Jewel … /dp/B0DZFXPS5M/

video for wintergreen oil transfers.
https://www.youtube.com/watch?v=JFxEwSq-wPI

Be sure to use in a ventillated area. the oil will be overwhelmingly pungent.

Another solution one could use is acetone+alcohol.
https://www.youtube.com/watch?v=HBIxvwZ_0og

But as others have stated, the part is really not required for operation. This is just for cosmetic considerations of having it.

Hello again weird_w,

Wow-- thank you. sounds like fun. perhaps a project for future days, especially as it seems the shield is not imperative. thanks again