VOGONS


First post, by lausvi

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Hi.

I ordered some PCBs of the AdLib replica board from PCBway. But due to my newbieness in these matters, I ordered the boards without the gold-plating on the card egde connector (they are beveled though). So now have five of these boards (and soon all the components needed) and I am wondering whether to use them at all. I know it would be best to have gold-plating, but would I be Ok to use these, or should I scrap them right away? I remember seeing some commercially-produced ISA boards without gold-plating and still working fine, so apparently they are not totally doomed.

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Reply 4 of 16, by Tiido

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HASL is going to ruin the slot it is put into (the gold plating in the slot is going to be damaged), if you're gonna use it in that one slot it should not be moved into any of the others.

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Reply 5 of 16, by AmiSapphire

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Yeah, made a Snark Barker with HASL a few years ago, and it turned out fine to an extent. Added solder paste to the card edge connector and re-flowed it, though. (Still have three PCBs left, however...)

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Reply 6 of 16, by lausvi

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Oh, ok. As I will probably be swapping the cards around, guess I won't be using these after all. I don't want to ruin any of my ISA slots nor the new board!

I didn't like the fact that the replica didn't have an AdLib logo, so I guess I'll add it myself (with a clear marking that it is a replica, will also slightly adjust the potentiometer's position) and order myself some proper boards with gold-plating on the edge connector, then!

Reply 7 of 16, by whaka

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Tiido wrote on 2021-09-03, 21:03:

HASL is going to ruin the slot it is put into (the gold plating in the slot is going to be damaged), if you're gonna use it in that one slot it should not be moved into any of the others.

how is it possible ?
tin is more soft than gold plated (or not) "teeth" in the connector.
there's absolutely no issue unsing HASL finish in connectors, but HASL is more prone to wear by plug/unplug cycling and oxidation, that's all.

what about those 72 pins ram that use tinned fingers into gold plated socket ? 😀

edit : i think you maybe misunderstood with the edge beveling, which is usually not an offered option by pcb manufacturer with HASL.
but this is not an issue with isa slot, or any edge connector of that kind.
but it can be problematic with pci like connectors (mca, and other of that kind) because the non beveled edge can sometimes bend the connector contact.
so, in that case better choose ENIG, or something similar with beveling option. otherwise, just do the bevel by hand, with mini wood file for exemple.

Reply 8 of 16, by Tiido

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Gold and tin freely amalgamate, upon contact the gold is diffused into the tin. This is the mechanism by which the connector is damaged, losing its gold plating and getting exposed to oxidation effects. This is something I see causing problems time and time again in stuff like MegaDrive + MegaCD, as all MD1s have solder plated edge connector, while the MCD connector isn't. There are occasional weirdnesses that only go away for a while after the connectors have been exercised.

Similarly as a young and poor guy 10+ years ago, getting my first PCBs made in china for the MegaDrive, only option was solder plating and those cartridges always caused problems with the cartslots. The machine where I used those carts had to have its slot replaced as it simply stopped being reliable and also thanks to the solder leftovers in the slot it began to damage actual game cart contacts too. You could clearly see the gold plating turning into grey solder color at the contact parts (and you cannot just rub it off, the gold gets infused with the solder due to the amalgamation process). Those carts also work unreliably in other undamaged slots and will contribute to destruction of them...

You 100% definitely want gold-gold contact interfaces in these things.

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Reply 9 of 16, by maxtherabbit

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whaka wrote on 2021-09-09, 06:00:

edit : i think you maybe misunderstood with the edge beveling, which is usually not an offered option by pcb manufacturer with HASL.
but this is not an issue with isa slot, or any edge connector of that kind.

this is false, an unbeveled card edge will wear down any card slot, ISA or otherwise

Reply 10 of 16, by whaka

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not false, isa like connectors already have well curved and spaced "teeth" so it's really really more tolerant to non beveled edge.
not like pci like connectors.

Tiido : yes, i tend to forget we don't speak about 100% tin and 100% gold 😁
there's probabely others metals which can interact in each other. but anyway, for prototyping, using HASL is not really a concern.

Reply 11 of 16, by BitWrangler

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Tiido wrote on 2021-09-09, 12:03:

You 100% definitely want gold-gold contact interfaces in these things.

Gold plated ISA slots seem kinda rare to me, they must be nickel or something.

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Reply 12 of 16, by wiretap

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99%+ of ISA slots you'll be putting an Adlib in will have phosphor bronze mating pins. It is corrosion/oxidation tolerant to lead and tin -- of course tin because it is partly made of tin itself. Also, lead is often melted in with it on purpose to give it better casting ability and flexible properties. Many early ISA cards had tin/lead edge connector fingers.. I have several in my collection, and I still have many in service at work with 30 years of runtime on them.

I've never seen gold plated ISA slot contacts on any motherboards I own. That would have been a special order item of the era, or only used in high end industrial boards requiring precision contact/connection for signal integrity. When ordering new parts from Tyco, TE Connectivity, etc - it is now common to see gold plated contacts in ISA slots since it costs far less to manufacture today.

Last edited by wiretap on 2021-09-09, 17:48. Edited 1 time in total.

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Reply 13 of 16, by maxtherabbit

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whaka wrote on 2021-09-09, 15:35:

not false, isa like connectors already have well curved and spaced "teeth" so it's really really more tolerant to non beveled edge.
not like pci like connectors.

you are correct in that it is less destructive to an ISA slot than a PCI/VLB/MCA one

you are incorrect that it is "not an issue with isa slot"

Reply 14 of 16, by BitWrangler

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Also we're dealing with old stuff where it's not inconceivable that a contact has a minor pit or something that will snag on a sharp edge and then pull the contact over and mangle it as the board is inserted further.

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Reply 15 of 16, by retardware

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wiretap wrote on 2021-09-09, 16:52:

99%+ of ISA slots you'll be putting an Adlib in will have phosphor bronze mating pins. It is corrosion/oxidation tolerant to lead and tin -- of course tin because it is partly made of tin itself. Also, lead is often melted in with it on purpose to give it better casting ability and flexible properties. Many early ISA cards had tin/lead edge connector fingers.. I have several in my collection, and I still have many in service at work with 30 years of runtime on them.

I have never seen problems with HASP slot fingers, too. They were really common back then.

Well, the only problem is the oxidation which can also be seen in the OP's photo. But that can be wiped of using vinegar.

wiretap wrote on 2021-09-09, 16:52:

I've never seen gold plated ISA slot contacts on any motherboards I own. That would have been a special order item of the era, or only used in high end industrial boards requiring precision contact/connection for signal integrity. When ordering new parts from Tyco, TE Connectivity, etc - it is now common to see gold plated contacts in ISA slots since it costs far less to manufacture today.

Maybe because of ROHS?
The ISA slots in my 2016 LGA1150 industrial mobo of my new DOS gaming build are indeed different than those I am used from old consumer mobos.
Much better grip, maybe indeed harder metal. Will examine them more thoroughly soon.

maxtherabbit wrote on 2021-09-09, 14:28:

this is false, an unbeveled card edge will wear down any card slot, ISA or otherwise

True... a card with burrs is cruel to the slot, like a scraper.
Just do some careful work using a fine file to remove and round off the burrs so that the card slides into the slot smoothly.

BTW, back in Apple II times when I etched my own boards, I manually soldered on tin plating to prevent the copper corrode. This was far thicker than electrolytic plating and indeed the slot got somewhat "dirty" over time after many plugs/pulls.

Reply 16 of 16, by lausvi

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wiretap wrote on 2021-09-09, 16:52:

99%+ of ISA slots you'll be putting an Adlib in will have phosphor bronze mating pins. It is corrosion/oxidation tolerant to lead and tin -- of course tin because it is partly made of tin itself. Also, lead is often melted in with it on purpose to give it better casting ability and flexible properties. Many early ISA cards had tin/lead edge connector fingers.. I have several in my collection, and I still have many in service at work with 30 years of runtime on them.

Thanks, that makes total sense and I kinda wondered that as I have some tin/lead edge connector ISA boards too (and as the ISA socket contacts never really looked like gold either).

Also thanks for the whole discussion on the topic 😀

I put in an order for some other PCBs and decided to re-order the AdLib boards as well. Partly because of the tin/lead plating and partly because the first version didn't have that lovely original AdLib logo! So I added one myself, and did some minor adjustments to the layout and ordered new ones. I just received the boards and they look really nice!

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