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What a mess...130XE RAM


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abort.jpg

 

Yeah, it actually works 100%.

 

Another RAM failure this week meaning more destroyed pads and more jumper wires. :mad:

Seems like every two years one decides to fail and this week was one in the extended memory.

No test screen, just noticed when loading DOS I'd get an error message about not being able to write to disk and the XE version of Atariwriter Plus would not load. Turned out to be U31.

 

Everything I've tried ends up in ruined pads. Vacuum desoldering iron, soldering station set at various temperatures and this time I used a dremel to cut the legs and then heat and pull each out individually and I still killed 4 pads!

 

In the future, would it be possible to cut out all the RAM with a dremel and use something like a 320XE? If not, next time red blocks pop up or DOS can't load the RAM Disk, this thing is getting chucked into the trash can. It's like the damn board is made out of paper mache.

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The technique for desoldering is as/more important than the gear used.

 

Not that a lot of mine has been on XE but the best desolder technique I found, use an iron with tapered tip at about 240 Degrees C.

Apply the heat to the side of chip pins. So, the soldering iron will be almost parallel with the pin, almost right-angled to the motherboard.

Don't actually touch the motherboard, just allow the heat to transfer. Then use solder sucker from the non-component side of the motherboard after applying about 10-15 seconds worth of heat.

Once you get good, once per pin will be enough. Leave the power/Gnd pins with larger traces for last, they're usually harder as the fatter trace acts as a heatsink. For some chips it's just easier to prize the chip out while applying heat then clean up the residual later.

 

Using such method you should be able to almost guarantee no damage to the motherboard and you can reuse the ICs too. Though with faulty Ram you tend to just throw the lot out.

 

To hold the motherboard during the operation, either a hobby vice or use a cardboard box with slots cut to hold it for you.

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The copious use of flux on both sides of the pcb cannot be stressed enough as well. If all the solder solder doesn't come through quickly on the first attempt, re-solder the joint, flux both sides of the board, and try again.

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The technique for desoldering is as/more important than the gear used.

 

Not that a lot of mine has been on XE but the best desolder technique I found, use an iron with tapered tip at about 240 Degrees C.

Apply the heat to the side of chip pins. So, the soldering iron will be almost parallel with the pin, almost right-angled to the motherboard.

Don't actually touch the motherboard, just allow the heat to transfer. Then use solder sucker from the non-component side of the motherboard after applying about 10-15 seconds worth of heat.

Once you get good, once per pin will be enough. Leave the power/Gnd pins with larger traces for last, they're usually harder as the fatter trace acts as a heatsink. For some chips it's just easier to prize the chip out while applying heat then clean up the residual later.

 

Using such method you should be able to almost guarantee no damage to the motherboard and you can reuse the ICs too. Though with faulty Ram you tend to just throw the lot out.

 

To hold the motherboard during the operation, either a hobby vice or use a cardboard box with slots cut to hold it for you.

 

 

Thanks for the tips. That's one technique I haven't tried and will give it a go the next time around.

My dad taught me how to solder when I was about 5 years old, and in the last 40 years, this XE board is the only thing that's been kicking my ass each time. I've just never experienced anything so fragile...not even in any other Atari 8 bits that I've owned.

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I use a large pump action solder sucker. Seems to do the job OK at removing chips. I think it's all in the technique.

I've done work on an XEGS board, so it's similar quality. I haven't experienced any problems working on it.

 

Heat up the pin with the iron until you can start to see the solder liquefy, and the trigger the solder sucker over the pin at a 45 degree angle as the tip of the sucker rests on the iron.

Done properly, there will be a visible hole.

 

The trick with removing chips from a circuit board is to ensure that each chip pin is free from the edges of it's hole in the board BEFORE you attempt to remove the chip.

After sucking solder out and seeing the visible hole, use the tip of the soldering iron to push the pin back and forth to ensure that any lingering solder is not still connected to the pin.

If it is, I try sucking the solder again until I can see a visible hole.

Done properly the pin should be able to "bounce" as you tap it with your iron.

 

You NEVER attempt to remove the chip until you can verify that each pin on the chip is loose. Otherwise you have more work to do sucking the solder out.

Attempting to pull out a chip that isn't completely desoldered can DESTROY your motherboard as you may end up ripping up the tracings connected to each pin of the chip.

 

Often times there is one pin that just won't seem to desolder and is holding up the chip removal (pin 1 usually). You can get away with removing the chip with heat applied to that pin so you can lever the chip out.

 

After removing the chip, make sure you replace it with an IC socket so you never have to do this again!

Solder in the socket pins (make sure you line it up the right way with the chip indentation), and let the socket cool down for about 10 minutes or until cold before reseating the chip.

If you don't give the socket time to cool down before re-inserting the chip, you can often end up warping the socket and the chip may not seat properly -- even possibly falling out of the socket!

 

It's a good idea to practice desoldering chips on an electronics board that you don't care about first - before you apply your skills to a board that you DO care about.

Edited by Neo-Rio
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Been doing this for decades on everything from high quality circuit boards to Chinese crap without a problem...it's just that this XE board does not want to cooperate. The little eyelet pads just pop right off the motherboard, often still attached to the trace.

I bought this XE from a thrift store about 20 years ago and it was still sealed in the box so I know that no one has been in it. There were already several RAMs replaced (different brand) with sketchy looking solder joints.

Look at the bottom left RAM and then to the lower right of the right RAM. I have a feeling these boards had failures right off the assembly line and had to be repaired by hand. My 400 and 600XL were built like tanks compared to this.

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Been doing this for decades on everything from high quality circuit boards to Chinese crap without a problem...it's just that this XE board does not want to cooperate. The little eyelet pads just pop right off the motherboard, often still attached to the trace.

Oh s&^*t that ain't good.

 

Never had that before, but I have had a C64C late revision motherboard with solder that was seemingly impossible to melt properly. It caused me no end of grief.

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In fairness, I've been working on these boards for years too but a while ago I happened upon a 130XE mainboard which simply could not survive desoldering at all. First job was removing the broken power switch and the thick traces parted company with the board as I was heating up the legs. Fit only for the bin. Perhaps you've got one of those boards. ;)

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What Neo-Rio said is EXACTLY right. I've often described that technique on here myself over the years.

 

I would add the following:

 

The key to avoiding delamination on crappy boards is reducing the heat and application time required in the desoldering process. The less heat you have to apply and the less time you have to apply it, the less the cheap board gets baked and the less likely a pad or trace is to come "unglued".

 

 

A) On every chip pin pad EXCEPT Power and Ground pins (the ones with thick traces or ground planes connected to the pads), TURN DOWN THE HEAT as much as possible. 550F is risking delamination on crappier boards.

When youve done all the non-power/ground pins, turn the heat up an additional 50-100 degrees F, and do the power and ground pins as quickly as possible.

 

B) Alwayse use plenty of liquid flux applied to the solder joints before applying heat too. IF you use a quality flux, the heat requirements (and time of applying heat) goes down.

You see some people suggesting to apply new solder to the joints to make them suck out easier. These people misunderstand. The actual problem here is that the solder has become oxidized with age and therefor is resistant to fast heat transfer. What is actually needed is flux. In cases where the surface of the solder is extremely oxidized from age/environment, you may LIGHTLY scrub the surface of the joints with a tiny soft brass brush, and then apply liquid flux, then heat/desolder...

Edited by MEtalGuy66
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