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mrpi64
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Re: My new board

Mon Jul 07, 2014 4:53 pm

MrEngman wrote:
drgeoff wrote:
MrEngman wrote:I have used a solder sucker often in the past to unsolder DIL devices without damaging them.
1. Techniques for removing a duff chip for replacement by another are not necessarily the same as those for removing a good chip for use again elsewhere.

2. A solder sucker needs to be held at just the right distance from the joint. Too far away and it doesn't suck the molten solder. Too close and the recoil action when the piston is released causes the nozzle to strike the board potentially damaging the pad if that is a concern.
I used to use the solder sucker to remove components to use again, not to junk them. e.g. PLDs that I wanted to change the programming of when they were solder directly into the board instead of fitted using a DIP socket.

And , yes, you have to be careful using it or else it can cause damage. However, where I worked i had no other option and so became reasonable proficient.



MrEngman
Yeah, there is a PGA device soldered onto it. How the heck can I safely desolder that? Looks like I have to just risk burning it, or throwing it away.
I'm happy to help.
https://www.raspberrypi.org/forums/viewtopic.php?f=78&t=51794 - List of games that work on the Pi.

MrEngman
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Re: My new board

Mon Jul 07, 2014 6:07 pm

mrpi64 wrote:Yeah, there is a PGA device soldered onto it. How the heck can I safely desolder that? Looks like I have to just risk burning it, or throwing it away.
I was generally removing 20/24 pin DIL devices. What is your PGA device, the HD63450? I certainly wouldn't be happy trying to desolder that.



MrEngman
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mrpi64
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Re: My new board

Tue Jul 08, 2014 7:15 am

MrEngman wrote:
mrpi64 wrote:Yeah, there is a PGA device soldered onto it. How the heck can I safely desolder that? Looks like I have to just risk burning it, or throwing it away.
I was generally removing 20/24 pin DIL devices. What is your PGA device, the HD63450? I certainly wouldn't be happy trying to desolder that.



MrEngman
Yeah, it is. Looking back at the datasheet, it supports wave soldering, up to 260 degrees for 10 seconds (max), and then the temperature has to go to 150 degrees or lower within 6 seconds. I think, that with a bit of braid, I can just about scrape by.
I'm happy to help.
https://www.raspberrypi.org/forums/viewtopic.php?f=78&t=51794 - List of games that work on the Pi.

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mrpi64
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Re: My new board (With better pictures)

Tue Jul 08, 2014 2:34 pm

Thanks for all of your advice. I have desoldered a DRAM chip, the CMOS battery holder, 7 LEDS (the 8th died in the process), and almost finished another DRAM chip.
I'm happy to help.
https://www.raspberrypi.org/forums/viewtopic.php?f=78&t=51794 - List of games that work on the Pi.

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mrpi64
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Re: My new board (With better pictures)

Wed Jul 09, 2014 1:36 pm

More parts: 50MHz xtal (what for? CPU runs at 20MHz), Floppy Drive Controller, and an RTC, plus a burnt circuit board.
I'm happy to help.
https://www.raspberrypi.org/forums/viewtopic.php?f=78&t=51794 - List of games that work on the Pi.

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mrpi64
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Re: My new board (With better pictures)

Fri Jul 11, 2014 2:09 pm

DMA controller is now off the board.
I'm happy to help.
https://www.raspberrypi.org/forums/viewtopic.php?f=78&t=51794 - List of games that work on the Pi.

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johnbeetem
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Re: My new board

Sat Jul 12, 2014 1:02 am

drgeoff wrote:
mrpi64 wrote:The AT&T chip is a "Field-Programmable Gate Array".
I'm not aware* that AT&T ever made FPGAs so if the chip really is a FPGA I'd surmise that the logo is on it because it is 'programmed' to perform some logic that AT&T required. Much less chance of it being part of a 'computer' than telco switching or transmission equipment.

(I would expect some clues as to the original maker of the 'virgin' FPGA to be on the package.)

* does not mean they do/did not - I'm not aware of everything. :)
My guess is that the ATT 3042 on your board is the same as a Xilinx part with the same number. IIRC, AT&T licensed FPGA technology from Xilinx with the right to extend the architecture. So they started with pure second-sourcing of the Xilinx 3000 series and then came out with their ORCA chips which were a new architecture. I link AT&T / Lucent sold the ORCA technology to Lattice Semiconductor, who has various FPGA lines including some very cheap small FPGAs Lattice got when they acquired Silicon Blue. Lattice also bought AMD's MACH CPLD technology.

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mrpi64
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Re: My new board (With better pictures)

Mon Jul 14, 2014 7:23 am

I'm looking through the AT&T chips datasheet - it's a pain to program!
I'm happy to help.
https://www.raspberrypi.org/forums/viewtopic.php?f=78&t=51794 - List of games that work on the Pi.

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