PhilCs blog / the latest things hes broken(fixed)

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PhilC
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Re: PhilCs blog / the latest things hes broken(fixed)

Post by PhilC » Wed Sep 23, 2020 10:30 pm

@stephen_usher yeah that sounds about right to me but some will want emutos, etc, so best to let the roms and the cpus be individually selectable perhaps?

Re TF boards, I'm a little bit spoilt for choice at the mo, I have a 128mb one in a Mega 4, firmware needs tweaking to get 128mb, then one in an H4 which sits in an STFM case and then my new Mega is going to be treated to a TF536 as well.

I have too many other Ataris and really need to sell them on.
If it ain't broke, test it to Destruction.

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Re: PhilCs blog / the latest things hes broken(fixed)

Post by stephen_usher » Wed Sep 23, 2020 10:34 pm

You can have too many?!!!! :dizzy: :-D
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: PhilCs blog / the latest things hes broken(fixed)

Post by PhilC » Wed Sep 23, 2020 10:37 pm

@stephen_usher good point. (I did buy another Mega ST after all.)
If it ain't broke, test it to Destruction.

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Re: PhilCs blog / the latest things hes broken(fixed)

Post by JezC » Thu Sep 24, 2020 8:16 am

stephen_usher wrote:
Wed Sep 23, 2020 10:34 pm
You can have too many?!!!! :dizzy: :-D
According to the other members of the household, more than 20 (almost 30 really) is too many! :shrug: :lol:

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Re: PhilCs blog / the latest things hes broken(fixed)

Post by PhilC » Thu Sep 24, 2020 10:07 pm

I had a small delivery today, three TF536s in a box that i'll be fixing for a forum member.

So the first job was to have a good look at them under the microscope to determine what needed to be done. One of the things i've noticed when building PCBs with chips of this pitch is that its a must to have a microscope. The PCBs looked pretty clean when checked under a magnifier but when checked under the microscope its a lot easier to see why these boards had been troublesome.
Screenshot 2020-09-24 at 20.26.25.png
Screenshot 2020-09-24 at 20.26.25.png (686.21 KiB) Viewed 234 times
The solder ball isn't visible under the magnifier.
Screenshot 2020-09-24 at 20.28.21.png
Screenshot 2020-09-24 at 20.28.21.png (1.25 MiB) Viewed 234 times
Because the ram chips weren't quite centered some of the pins are bridging the gap between solder pads.
Screenshot 2020-09-24 at 20.23.05.png
Screenshot 2020-09-24 at 20.23.05.png (813.57 KiB) Viewed 234 times
And above you can see the solder bridging the two pins, again not visible under a magnifier.

The three boards have now been placed in the ultrasonic cleaner which showed other bridges that weren't obvious before cleaning. The chips were then fluxed up, reflowed and then squared up on the solder pads. More tomorrow.
If it ain't broke, test it to Destruction.

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Re: PhilCs blog / the latest things hes broken(fixed)

Post by PhilC » Sat Sep 26, 2020 6:18 pm

Done a bit more work on the three TF536s that I'm repairing today.

First job of the day was to get the chips better lined up with the solder pads. After id done this I had a fair few more bridges between pins. It looked like there was more solder balls hidden under the CPLD that decided to come out from under the chip whilst reflowing / realigning the chip.

I've now removed all of the solder bridges and fixed the loose pins,

Happy to report that board one now boots happily from IDS all the way to Workbench. Boards two and three now boot just fine to Diagrom but now I have to go and change the rom socket on the Amiga, as it only wants to boot when I press down on the rom.

If its not one thing, its another with these old retro computers
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Re: PhilCs blog / the latest things hes broken(fixed)

Post by PaulJ » Sat Sep 26, 2020 8:57 pm

@PhilC , how about an after picture. Always wondered what is good on the alignment. Did you remove the cpld or align it by some other method?

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Re: PhilCs blog / the latest things hes broken(fixed)

Post by PhilC » Sat Sep 26, 2020 9:01 pm

PaulJ wrote:
Sat Sep 26, 2020 8:57 pm
@PhilC , how about an after picture. Always wondered what is good on the alignment. Did you remove the cpld or align it by some other method?
I'll try and post one tomorrow.

I do the alignment the hard way, by pushing it left and right etc, until I get it right. With these shaky hands it takes a while at times.

There must be an easier way than the one I use.
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Re: PhilCs blog / the latest things hes broken(fixed)

Post by PhilC » Sun Sep 27, 2020 10:43 am

@PaulJ So this is an after photo. The board needs a quick clean which h I'll do after I've finished with it.

The alignment is not perfect but now none of the pins sit half on and off the pads.
Screenshot 2020-09-27 at 10.41.44.png
Screenshot 2020-09-27 at 10.41.44.png (3.2 MiB) Viewed 174 times
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Re: PhilCs blog / the latest things hes broken(fixed)

Post by PaulJ » Sun Sep 27, 2020 2:15 pm

PhilC wrote:
Sun Sep 27, 2020 10:43 am
@PaulJ So this is an after photo. The board needs a quick clean which h I'll do after I've finished with it.Looks
Looks good Phil.

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