Got 2 "junk" X68k's and need some advice

[H68k]

It seams I've finally got lucky after months on end of being outbid. and I've managed to get 2 X68ks that were being sold as "junk" from the auctions.

Ok without further a do, onto the conditions of both machines:

The XVI compact:

This poor little fellow looks like it's had it a bit rough, but I managed to get it working after striating some bent and crossed pins on some of the ribbon cables (I think this must of been causing a short that was preventing it from fully powering up), and some additional "bodge" fixes of my own.   

It would appear it's also been the unfortunate victim of what I can only describe as someone else's partial "bodge" recap job (with plenty of dodgy soldering ahoy), some of the SMD can caps have been replaced with generic cheap chinese made radials, but most of the damned original SMD caps remain in place.


Now for the second:

The X68030:

Now this one partly works, it fully powers up.. says Sharp personal workstation... lists the processor type amount of ram etc etc.. and then the screen remains blank. if left for some time, the generic "I have an error, please reset me" message will appear. while the screen is blank, pressing the interrupt button with produce the same result.

However.. in so many power ons, (it seams to do this after so long) it will display the message box on the screen asking for software, and the drive light will blink at the same time, as it should do. sometimes it will do it again after a reset. but after that, your back to square one. also on other occasions the drive motor of the 1st FDD will keep spinning and stopping every few seconds. and after a while, the generic "please reset me" error will appear on the screen.

I checked it over before powering it on, and couldn't find anything wrong with the ether  the motherboard or IO board, and it still has its original smd can caps. (I couldn't tell if any of these have leaked.. or bad.. as I can't get my cap testers probes in to get a reading on them)

I suspect it might be something to do with bad caps on ether the FFD logic boards or the IO board?


Now onto the questions:

What's the best method of removing these dreaded SMD can caps? I've heard and read about multiple methods of ridding these damn things from a PCB.. but some of them sound a little... scary.. and I don't fancy dealing with lifted or ripped off solder pads... :-/

Would attempting to recap the logic boards of the 68030's 5 and-a-half FFDs be worth a shot? I have the experience and tools to deal with them... just not those damned SMD ones.

[sleepydwarf]

After my own recent experiences with a compact red zone (see red zone troubleshooting assistance thread) I highly recommend you don't use an iron to remove the caps. May be partly my own fault as I hate doing anything surface mount, but I lifted a number of pads when I first removed caps.

I ended up removing all the caps again, I borrowed a solder rework station and used hot air. The one I borrowed was similar to this

http://www.ebay.co.uk/itm/New-3in1-Soldering-Iron-SMD-Rework-Station-Hot-Air-Gun-Kit-DC-Power-Supply-/151341144553?pt=UK_Home_Garden_PowerTools_SM&hash=item233ca299e9

Removed all caps in one go without any problems at all using that.

Good luck getting them both running!

[eidis]

 Hi H68k !

Sorry for the late reply ! Just as Sleepydwarf said, hot air rework station is the way to go. Most of the times the patient is fully cured after a recap. Recap everything that you can. I learned the hard way that bad caps on floppy drives can render them inoperable. You could also try clearing SRAM by holding down CLR while powering on the machine and it should give you a prompt that will ask you if you want to erase the SRAM and return all settings to their defaults.

Keep the scene alive !
Eidis

[RobIvy64]

Oy!!

Do NOT use a hot air gun to remove SMD aluminum caps!!

You'll risk delaminating your PCB from repeated heating and cooling in the same areas.

I use hot tweezers. Heats both legs simultaneously, and the cap comes right off. It couldn't be easier.

[kamiboy]

That is what I did, the tweezers that is.

I even replaced every SMD cap with one of the same type, and even size, yes I measured them all. I also only used super high end rubicon and nichicon caps. Cost me a damn fortune it did, and if you think desoldering SMD caps is an exercise in frustration then try soldering some back on. Shudder...

[eidis]

 Hi RobIvy64 !

Thank you for the valuable tip, was completely unaware that such tool exists. This looks like a must buy. Can you recommend a good model ? Thanks !

Keep the scene alive !
Eidis

[BlueBMW]

Honestly I use some small snips to grasp the cap bodies and work them until they brake free from their legs.  At that point I pull off the plastic base put some flux on the pads and use a conventional iron to scoop out the rest of the cap leg.  Then I use some desolder braid to finish removing the old solder and clean the pad.

[H68k]

Thanks for the advice. it proberly wont be the end of july or early august before I get some more free time spare(I have some RL and annoying work related crap to get out of the way first), before i can start properly looking over them and begin working on them.

in the mean time, i'll plot my next course of action on how to tackle the problem, and then buy the tools/parts misc stuff etc i need to deal with the smd cap's


sleepydwarf:

After a quick bit of research, it seams to me like most of these cheap chinaman made hot air rework tools and heat guns are just accidents waiting to happen (from one horror story i read on the eevblog forum, someone brought a cheap hot air rework station, and found it had live mains WIRED to the metal shielding of the hot air tool).

It seams you can get a lot better made hot air rework tools from other Chinese firms, but they want there moneys worth for them.

Following RobIvy's advice, I think I'll try the heated tweezers method.


eidis:

From what I've seen on youtube, de soldering tweezers seam to be a precise, non destructive method of removing SMD components from PCBs.

but I read somewhere, there not so good at removing the SMD can caps... (was the poster of this on the forum i read it from doing it wrong I wonder?)


BlueBMW:

this seams a little scary BlueBMW.. but i did see some guy's video on you tube had a smiler technique.. he used some flush cutters and cut the smd can cap just above the plastic trim, perpendicular to the solder pads of the pcb.

[kamiboy]

I use these to solder everything, not just SMD's.

http://www.ebay.com/itm/902-SMD-Hot-Tweezers-Soldering-Iron-Desoldering-ESD-Station-Ship-From-Canada-/310531697774?pt=LH_DefaultDomain_2&hash=item484d21ac6e

[BlueBMW]

Yeah I use flush cutters to do it.   Its easy enough if you slowly and carefully wiggle the cap back and forth until the legs break from the cap body.  If youre careful you wont damage pads.  It can be really hard to remove caps that are heavily corroded with heat.  Breaking them off and then cleaning always seems to work good for me.

[eidis]

 Hi Kamiboy and BlueBMW !

I guess it would be safe to say that both methods work well. How do you think, which one of them has less risk of lifting a pad which is beneath a leaked capacitor ?

Keep the scene alive !
Eidis

[BlueBMW]

It seems like every time i apply heat to a heavily corroded pad it has a tendency to separate from the board.  Removing the cap while cold gives me a chance to clean the pad some before trying to remove all the solder and start fresh on it. 

Ive not tried the soldering tweezers before but I suspect they probably work good.  But their tips look pretty small and probably cant push too much heat into the solder pads.  Thats not a problem except when there is heavy corrosion that doesnt allow the solder to melt and flow like normal.

[sharp]

I like to use a hammer to remove bad caps.
Just vicegrip the board to the table, and start wacking precariously.
It doesnt take a heavy blow, just the weight of the hammer alone is enough.

(laughs)

DO NOT DO THIS, IT IS NOT SUGGESTED TO USE A HAMMER TO REMOVE CAPS.

[neko68k]

bahaha >_<

[kamiboy]

Some times no amount of pussyfooting will prevent pads from being lifted. As long as they do not break you can always try to glue them back on the board, or just attach the cap and let the other good pad anchor it in place.

For heavily corroded pads I turn the heat all the way up and that usually does the trick. 

[eidis]

 I think that someone, who knows how to do it properly, needs to test both methods in order to reach a constructive opinion.

P.S. Kamiboy, a Gentleman never uses rude words in the presence of ladies.

Keep the scene alive !
Eidis

[sharp]

I really use a wick and braid usually. Recently though I got a soldersucking wand that is pretty nice. It has a rubber bulb, you just squish it, set the cone on the leg or point, wait until the edge is molten, then let go of the bulb, it sucks it up. Then I immediately blow the excess out of the end with a quick squeeze of the bulb into a cardboard box.. after it dries, you can just tip the box and it all goes to the corner.

It is made solely for desoldering, so the heat is just right, it couldnt lift a pad I dont think.
Really nice, it also seems to have an interchangeable tip. Sometimes though I have trouble with occasional points. Maybe its corroded? maybe I didnt let the gun heat up enough? Maybe the tip wasnt just right for the point? but yeah, I still suggest having 1. Its a great thing to have if you need to replace a 40 pin dip or something.

[ApolloBoy]

For surface-mount caps I usually grip them with pliers and twist them off. I used this technique back when I worked on TurboDuos and not once did I ever damage the board.

[H68k]

I've also seen this technique be used in some guy's console repair video on you tube.. it made me cringe every time he did it.. I'm aiming for a method that has the lowest solder pad mortality rate as possible.

but yes.. The PC engine(Turbo GFX) also suffers from the same problem later X68k models do, cheap and nasty SMD cap's that start to give in and/or leak after not to long of the machines use. (the older X68k models, with through hole radial caps actually managed to outlast the newer SMD equipped ones.. rather ironicly)

with most of them. it's just a case of fitting ether new radial or SMD caps(that a lot more reliable than they used to be).. and they'll work just as good as the day they rolled off the production line.