exxos blog - random goings on

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exxos
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Re: exxos blog - random goings on

Post by exxos »

Maybe we should have a competition of how many bodge wires this this will need :lol:

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Re: exxos blog - random goings on

Post by stephen_usher »

With regards to your soldering, have you seen this stuff?
https://camelliaer.com/products/20g-bga ... n1RWNgh7Bk
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Re: exxos blog - random goings on

Post by exxos »

stephen_usher wrote: Tue Jul 06, 2021 8:57 pm With regards to your soldering, have you seen this stuff?
Not seen that no. Looks like T4 paste. I am using T5 for small stuff. But I may try it on some simms when i've used all my current paste.
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Re: exxos blog - random goings on

Post by stephen_usher »

It's more the formulation that's of interest. Low temperature with wetting agents and flux.
Intro retro computers since before they were retro...
ZX81->Spectrum->Memotech MTX->Sinclair QL->520STM->BBC Micro->TT030->PCs & Sun Workstations.
Added code to the MiNT kernel (still there the last time I checked) + put together MiNTOS.
Collection now with added Macs, Amigas, Suns and Acorns.
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Re: exxos blog - random goings on

Post by exxos »

stephen_usher wrote: Tue Jul 06, 2021 10:26 pm It's more the formulation that's of interest. Low temperature with wetting agents and flux.
Yeah looks interesting.
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viewtopic.php?f=17&t=1585 Have you done the Mandatory Fixes ?
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Re: exxos blog - random goings on

Post by exxos »

Not having much luck with the boards :( I built up one which looked dead. So tested some dram on a simm, then transplanted that onto a second board. Exactly the same. Beeped out the whole board, all looks fine. I checked I got ras cas right against the original Atari board, all seems fine. Double checked the lib for the ram chip and pinouts, seems fine.

I did swap around the address and data lines a bit. I only swapped data lines within the single ram chips. So it shouldn't matter. Address lines were swapped for better routing, but that shouldn't matter.

I did do a schematic for it and used the falcon ram connector from the remake boards. So shouldn't be a problem with that as a falcon ram board works fine in the H4. So that lib should be fine.

My simm adapter ram board didn't have a schematic. I just routed the PCB directly. Of course that works all fine. There's no real difference between the boards other than 1 uses a simm and the other just has dram soldered on to it.

:shrug:
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Re: exxos blog - random goings on

Post by exxos »

Has anyone seen a schematic for the falcon ram card ( no simm type) . I can't see it in the service manual or anywhere for that matter :roll:

I can't see i've done anything wrong ( but who knows?!) I can only think for some reason these 60ns chips don't work on this particular board, even though the same chips work on the simm I took them off :shrug:

EDIT:

Oh the RAM card is in the "bad copy" of the Falcon manual.. 32 chip version :shrug: Can't see anything wrong there anyway.. mystery :roll: Will look for some 100ns DRAM later.
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Re: exxos blog - random goings on

Post by exxos »

I've tried both RAM boards in my H4. One comes up 4 bits stuck high. The other shows 2MB valid RAM. So would have thought that would show some signs of life at least on the Falcon. :roll:
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Re: exxos blog - random goings on

Post by exxos »

Built up a third board with more paste on the pads this time. This one showed data bit 15 stuck high. So changed the DRAM chip then all hell broke loose. Put it under my hot air station blower and re-fluxed it and now it shows as 4MB on my H4. My Falcon it also shows as 4MB. So there must be one of the address lines bad somewhere. I will flux up and reheat the whole board again.

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But there is something going on with these J-lead packages not soldering down. Is what wrote off the previous batch of STE boosters as I tried to solder down the CPU to avoid using sockets and all their related problems. In the end I gave up. Now I am having what seems to be the same issues with the DRAM.

I can only really think either the paste just does not work or the PCB oven is not getting up to a high enough temperature. But even continuity checking and looking at the joints under a microscope, they all seem to look fine anyway.

See what happens after I heat up one of the board was only show up as 2MB next...

EDIT: nope 2MB still.

I found some SAC305 paste, so will give that a try.
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viewtopic.php?f=17&t=1585 Have you done the Mandatory Fixes ?
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Re: exxos blog - random goings on

Post by exxos »

Did not change anything using the other paste. This board also showed 2MB on the H4 :roll: I re-solder two of the chips by hand and now it shows 4MB. Problem is it also still shows 4MB on the Falcon :roll:

I continuity checked all the address lines and they are all connected on each chip. I bent over MAD10 on the H4 ( as it is currently 0V) and tied it to 5V. And it also shows 4MB fine. Without MAD10 connected the memory test goes nuts as expected.

Does anyone know of any programs for the Falcon for better diagnostics for memory ? sysinfo at least shows bank0 & bank1 RAM. Bank1 wasn't working which I re-solder that bank and then it showed 4MB. So RAS0, RAS1 must be working fine.

I am frankly perplexed to this problem. On the H4 high and low bytes are tied together. So 4MB test would actually be testing 8MB worth of RAM. Switching MAD10 manually would test the upper 8MB. So its all valid RAM.. but if its valid why doesn't the Falcon see it ?!

I noticed DETECT 1 &2 are not correct in my libs :roll: Though one is wired to 0v anyway, the other is floating, but easy to blob it to 0v.. but then it gives me 1MB :WTF:

Doublechecking on my simm adapter, both detect lines are wired to 0v...so that should be correct..

EDIT:

Measured the DETECTs again and one is open on my simm board, and on the Atari diagram, so I need to pull that pin as I think it should be 5V not 0v :roll:
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https://www.exxosforum.co.uk/atari/store2/ - All my hardware mods for sale - Please help support by making a purchase.
viewtopic.php?f=17&t=1585 Have you done the Mandatory Fixes ?
Just because a lot of people agree on something, doesn't make it a fact. ~exxos ~
People should find solutions to problems, not find problems with solutions.
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