What's the difference between the 486 and 386 mobos such that the ISA cards make contact when using the latter but not the former? Something doesn't sound right.

kolderman wrote on 2020-06-02, 21:39:

What's the difference between the 486 and 386 mobos such that the ISA cards make contact when using the latter but not the former? Something doesn't sound right.

Yeah, there should be no difference and the MB's both look the same and measure the same. Perhaps the cards that I'm using in the 486 (all 16bit ISA or VLB) simply make the issue more noticable as they need to make contact across a greater distance.

That might be it. It's weird, usually there is a gap between the backplane and the case rear for the ISA card brackets to descend into. Are you saying there is no such gap? A photo might help....

Yes, I have experienced that issue before, AT cases can be really frustrating. A few days ago I was dealing with a case where certain motherboards ended up with the top part slightly protruding from the tray, which made it impossible to put back the tray with the board installed as it would hit the chassis on its way in. I had to end up using another board that had the upper holes placed slightly above, so that case determined what board I had to use!

Regarding your problem, nylon standoffs that are slightly taller than the regular ones do exist, but I don't think they are widely available. Maybe you can use something as padding between the standoffs and the tray so that the nylon standoffs end up sitting as high as possible? For the metal hex standoffs you can use one or more of those round red washers between the tray and the standoff.

Can you post pictures of how the motherboard tray is screwed to the main chassis? Sometimes with these cheap cases some metal parts get bent which can cause for example the tray sitting lower than it should.

TheMobRules wrote on 2020-06-02, 21:53:

Regarding your problem, nylon standoffs that are slightly taller than the regular ones do exist, but I don't think they are widely available. Maybe you can use something as padding between the standoffs and the tray so that the nylon standoffs end up sitting as high as possible? For the metal hex standoffs you can use one or more of those round red washers between the tray and the standoff.

Can you post pictures of how the motherboard tray is screwed to the main chassis? Sometimes with these cheap cases some metal parts get bent which can cause for example the tray sitting lower than it should.

Yes some cases used taller or shorter motherboard standoffs. If you get a case without any then you will have to experiment to see how tall the standoff's need to be. Most often there is always at least a few standoff in even a used case that can be used to gauge the others you need. Note: never throw out any case standoffs that are spares as you never know when you may need a specific type/size/style.

I had to use some CACP01SOXT standoffs (6.3mm high) on one of my 486 cases. I had the same problem with it having the wrong standoffs installed from a previous owner. If you need some of the plastic slider type in 6.3mm, they are found by searching CACP01SOAT. They're readily in stock on several websites.

There are definitely a few different lengths of standoffs.
For screw-in ones:
5mm ones are really short
6.3mm are the normal ones
8mm are the long ones

On top of that you have standoffs that have either fine or coarse pitch threads.

Then you have some cases that use metal clip-in standoffs. They come in at least 2 different lengths.

That's very interesting. I had no Idea. I've been experimenting with nuts and bolts etc. today and I think I might have managed to get things level so that all the cards make good connection. One large nut, one small nut and four metal washers was the correct distance. More made the keyboard plug on the MB impossible to reach from the back of the case 😜

Now I suddenly have a completely different problem: My HDD doesn't work with the 486 working in 66mhz mode.. Well, It's all part of the fun I suppose 😜