130XE and the socket of doom

[CommodoreDecker]

I finally got the nerve to swap out the CPU in my recently-bought 130XE with my Rapidus that's sitting around.  Opening the case, I was happy to see that the CPU was socketed (and ceramic!).  Mobo rev 5.  

 

However, prying the CPU out -- it will not budge.  The plastic spudger yield no success.  The screwdriver tip scratched the edge of the chip but that's all.

 

I ran contact cleaner over the connections - thrice.  This made no difference.

There's no sign of glue or solder; in theory this thing should plip out with ease.  

 

I banged on the spudger with a rubber mallet - I did get 1mm loosened at the corner, but this amount of pressure seems dangerous, reckless, you name it.   I re-tested the machine and everything works, noting the ROM chip does get a little warm, but adding a heatsink will take care of that.

 

Are there unconventional ways to get the socket to loosen its contacts? Or should I try a few more rounds of contact cleaner and not breathe while spraying it?

 

Would WD40 work? Maybe there's rust that's the culprit... but I don't want to damage the plastic socket, chips or board.

 

Thanks!

 

(If I can get it loose, I'll also desolder the Mitsubishi RAM chips, add sockets, then look for a more proper brand of RAM... if I recall, the Mitsubishi batch used is known for premature failure.)

Edited March 23, 2023 by CommodoreDecker

[_The Doctor__]

MT is not Mitsubishi. Micron Technologies Ram that is standard black. Mitsubishi Ram might even have a silver coating.

[Beeblebrox]

Sounds like some serious oxidisation. I've had very stubborn 40pin IC's take a good prying out of their original single wipe factory sockets, but they all budge eventually.

 

You could do some serious damage to the PCB and the chip here. 

 

Can you upload an image or two so we can see?

 

EDIT; oh and before you say anything...yeah - I've got way too much time on my hands heh heh:  

 

Edited March 23, 2023 by Beeblebrox

[CommodoreDecker]

Thanks; I'll post some close-up pics this afternoon. Love that 10x optical zoom...

 

At face value the socket looked quite normal. But I definitely won't bang on it... Not worth risking any damage. It wasn't major banging with significant force, but any would be relatively considerable...    

 

 

Terrific image BTW.   

 

[woj]

Not sure what I would do, but when working on cars and mechanical force would not loose things, the next step (not always, some parts are equally heat sensitive as chips in our computers) for me is typically applying heat. Perhaps try reflowing the socket pins from the underside?

 

As you, I would also consider WD40, this thing can be difficult to clean, and I would defo use some fine equipment to just introduce tiny drops on the chip-socket contact surfaces, as you never know how plastics and such will react to it.

[xrbrevin]

desolder the socket with the chip still in?

then you can soak it in white vinegar or use a heatgun on it 😎

i cant imagine an XE having a ceramic Sally - never seen one in a 400/800 never mind any of the later models..

Edited March 23, 2023 by xrbrevin
bsod

[_The Doctor__]

did you push in before pulling?

[CommodoreDecker]

1 hour ago, _The Doctor__ said:

did you push in before pulling?

Yup. A gentle push in then a pull hadn't done anything.

[CommodoreDecker]

1 hour ago, xrbrevin said:

desolder the socket with the chip still in?

then you can soak it in white vinegar or use a heatgun on it 😎

i cant imagine an XE having a ceramic Sally - never seen one in a 400/800 never mind any of the later models..

 

I'm trying not to desolder, though I have the desoldering vacuum kit. The traces are said to be fragile.

 

If vinegar won't damage it, I'll let it sit in a shallow tray. Or I'll dab it into the socket.

 

Heatgun... like a hairdryer?

 

Photos of mobo (both sides) and close-ups of the CPU.  I think I can guess which one is Sally, LOL:

[+kheller2]

You could try a jewelers screwdriver and shim it between the CPU pins and socket metal tabs, one at a time to see what's going on.  Be gentle.

 

By the way, something I didn't notice before, that jumper/bodge wire on the REV 5 board.  It's not on the REV 3 or 4.  Can't believe they still screwed up the power lines.

[+Stephen]

Also, make sure you weren't trying to pry under the socket, rather than in between the IC and socket.  It's an easy thing to do.

[_The Doctor__]

Try not to let your prying device scrape or touch the pcb and surrounding components either. sockets are not solid filled and under the chip are normally open to the PCB

[Beeblebrox]

All great advice. I think if it still refuses to budge and you have good enough soldering skills, I'd go with an earlier suggestion and carefully desolder the whole socket with the cpu in it. Sourcing a replacement cpu isn't all that hard or expensive, plus even if you did get the cpu out of the existing socket, the socket itself might not be ideally used anyway going forward. Better to replace the entire socket imho. Plus you will be able to check the state of the PCB and vias/traces underneath once all removed anyway. 

 

 

Edited March 24, 2023 by Beeblebrox

[mutterminder]

I wouldn't desolder it just yet.  I usually use one of these when pulling large DIPs. I've found them to work well even on hard to remove chips.

 

[+Stephen]

1 hour ago, mutterminder said:

I wouldn't desolder it just yet.  I usually use one of these when pulling large DIPs. I've found them to work well even on hard to remove chips.

 

Quoting for the WT actual F  is this!

[_The Doctor__]

it's a chip puller

You have to be pulling our legs right?

[Beeblebrox]

Now that's interesting. I'd not realised you got chip pullers for the likes of 40pin ic's. Makes sense. 

 

 

Edited March 26, 2023 by Beeblebrox

[+Stephen]

11 hours ago, _The Doctor__ said:

it's a chip puller

You have to be pulling our legs right?

No - I've never seen something like that before.

[CommodoreDecker]

  

On 3/23/2023 at 4:25 PM, kheller2 said:

You could try a jewelers screwdriver and shim it between the CPU pins and socket metal tabs, one at a time to see what's going on.  Be gentle.

 

By the way, something I didn't notice before, that jumper/bodge wire on the REV 5 board.  It's not on the REV 3 or 4.  Can't believe they still screwed up the power lines.

 

Tried that earlier, as the metal screwdriver would be stronger than the plastic.  I definitely took my time so I wouldn't accidentally scrape the board.  Got one edge pried out a little (think 0.5mm), maybe a tad more for the opposite side, but the middle will not budge. On the plus side, the 130XE still runs rock solid despite this attempt.  

 

17 hours ago, mutterminder said:

I wouldn't desolder it just yet.  I usually use one of these when pulling large DIPs. I've found them to work well even on hard to remove chips.

 

 

Thanks for the info!  I'll look it up.   Until then, I'll be retrying the contact cleaner spray a few times and seeing if that helps.  If not, I'll keep this one as it stands and get another XE one day and see if it's socketed and then put the Rapidus into it... wouldn't hurt to have a backup to work or experiment on anyway.

 

15 hours ago, _The Doctor__ said:

it's a chip puller

You have to be pulling our legs right?

 

I don't think that thing is large enough to pull legs with... LOL

 

On 3/24/2023 at 2:55 AM, Beeblebrox said:

All great advice. I think if it still refuses to budge and you have good enough soldering skills, I'd go with an earlier suggestion and carefully desolder the whole socket with the cpu in it. Sourcing a replacement cpu isn't all that hard or expensive, plus even if you did get the cpu out of the existing socket, the socket itself might not be ideally used anyway going forward. Better to replace the entire socket imho. Plus you will be able to check the state of the PCB and vias/traces underneath once all removed anyway. 

 

 

 

I've a desoldering vacuum, spare copper braid, enough stamina, and I don't have shaky hands yet so it may be possible.  Was hoping that the socket itself would have made this swap easy... then again, in the 800XL I did run into problems where the Rapidus' round pins would not stick in its original socket that required the thin rectangular pins - ugh. I suspect the same issue would happen here.

 

[CommodoreDecker]

I found another 130XE - rev B motherboard (wow).  Used it for practice fodder. Was able to remove the CPU's solder and added a socket. 

 

Due to the delicate nature of the 130XE motherboards and contact traces, I took over an hour in carefully vacuuming out solder. In some cases I had to add solder to a joint and then vacuum it all out to properly loosen it without damaging. This process is NOT easy or quick, and is absolutely not recommended for beginners like me.  I did lightly scratch part of the board with the soldering iron tip, but took a photo of the scratch and thankfully none of the traces was cut through. 

 

One thing about the Rapidus is that, even in the 130XE, one needs a riser or other means to get the thing up and over the chassis' cartridge mount.  For which using 3 spare sockets induced so much electrical resistance that I had weird anomalies with screen color.  After removing those those, removing the board from the chassis, and placing Rapidus directly into the socket, the color anomaly went away. I would think of other ways to mount the thing after a thorough test.  I would get random reboots several minutes into game play.  Even with setting the option to allow cartridges, no cartridge worked.  I did further reading and found other people had the same random rebooting problem, so I'm officially giving up on Rapidus for those flight simulator and other wireframe 3D games to improve FPS.

 

It's better late than never, but I now feel more confident in desoldering the delicate XE motherboards, if I ever wanted to add sockets should RAM go out.  The board I tested on had "mT" on all the RAM chips. I believe that is Micron brand... that's also the brand that, for the XE line, had a bad failure rate, if I remember other posts correctly, such as this one: 

 

  If it's just holding data after a power-down, I'd just power off for 1 minute and by then the banks should clear...

 

One other thing - after removing the Rapidus, plonking back both the original CPU and a spare working one (from 1983) had issues with their metal contacts not making a steady connection into the socket -- the socket I put in has round "o" holes meant for Rapidus, whereas every 6502 I have needs the regular "-"  dash-shaped sockets.  The spare CPU, once I was able to get it solidly in the socket to boot, remained stable, but that style of socket isn't meant for the flat CPU contacts, so I will remove that new socket and put in a tried and true one.  Or re-solder the original CPU (made in 1985) back in without a socket.  

 

Once I decide what to do with the new socket, I'll do a replacement of the capacitors as well. 

 

[xrbrevin]

2 hours ago, CommodoreDecker said:

the socket I put in has round "o" holes

these are the more expensive type, known as 'turned pin'.

 

2 hours ago, CommodoreDecker said:

"-"  dash-shaped sockets

these known as are single or (preferrably) 'double-wipe'

 

chips are fine in both but turned pin are built to a higher standard using a machining process

[CommodoreDecker]

On 4/3/2023 at 11:26 AM, xrbrevin said:

these are the more expensive type, known as 'turned pin'.

 

these known as are single or (preferrably) 'double-wipe'

 

chips are fine in both but turned pin are built to a higher standard using a machining process

 

Thanks for the info!

 

About a year or more ago, I did try the Rapidus in an 800XL, but the turned pin connectors never remained stable and the device kept getting loose in the double-wipe socket. I believed at that the contacts had to be of the same type as I had some (different) stability issues for it as well.  I'd say it was a defective unit, except I own two Rapidus modules - the second unit I bought with the XL adapter that had the elongated ribbon cable, since the module couldn't sit directly on the CPU socket due to chassis size limitations. The issues I had on the 800XL were later attributed to the Rapidus and XL ROM sockets always getting loose and I shelved the project, until now.    

 

I'll probably give the 130XE another go this weekend; I saw this post, which had tips and external sites:

 

 

Will look into firmware upgrades, too; this makes for a fun weekend hobby. I envy all those sockets too, heh... but it can be done.  

 

Though I'm curious to know how he mounted the Rapidus without needing three 40-pin sockets rising up between Rapidus and main mobo socket to fit it right, ha!   My XE Rapidus has a different connector at the lower-right of it; three pins sticking out instead of the trapezoidal-shaped socket.  I had matched up the pins on MMC and Freddie right per the online documentation and I see where the traces on the mobo go to (my ground was in a different place and I used a bit of wire, which also adds to resistance), but I soldered onto the chip directly - without causing any shorts. Even better, the photo shows a much more elegant solution.