If you have a P1 system...prepare to tear it apart

Lyos Gemini Norezel · Post by **Lyos Gemini Norezel** » Mon Feb 02, 2004 5:42 pm

Hey ya'll... check this out... I was searching various parts on an ancient P1 one system and found that most of the chips have no datasheets... the I looked up this chip: SMC(manufacturer) FDC37C932(part #)
and I found this page on google:
http://www.smsc.com/main/tools/disconti ... 93xapm.pdf

It's a super I/O chip... might allow us to do what we thought was impossible on a 6502 system.
Lyos Gemini Norezel

Kotlowy · Post by **Kotlowy** » Fri Feb 13, 2004 3:23 pm

Quote:

The FDC37C93xAPM incorporates a keyboard interface, real-time clock, SMSC's true CMOS 765B floppy disk controller, advanced digital data seperator, 16 byta data FIFO, two 16C550 compatable UARTs, one Multi-Mode parallel port which includes ChiProject circuitry plus EPP and ECP support, IDE interface, on-chip 24mA AT bus drivers, game port chip select and two floppy direct drive support, etc...

wow, good find. the tricky part is getting the original component or try and desolder it from old motherboards.

leeeeee · Post by **leeeeee** » Sat Feb 14, 2004 12:29 am

Kotlowy wrote:

the tricky part is getting the original component or try and desolder it from old motherboards.

Hot air paint stripper, just watch it doesn't blow away once the solder melts.

Lee.

Lyos Gemini Norezel · Post by **Lyos Gemini Norezel** » Sat Feb 14, 2004 4:18 am

Kotlowy wrote:

the tricky part is getting the original component or try and desolder it from old motherboards.

Ye... very difficult.

leeeeee wrote:

Hot air paint stripper, just watch it doesn't blow away once the solder melts.
Lee.

How much does one of these cost and where would I find one?
Lyos Gemini Norezel

GARTHWILSON · Post by **GARTHWILSON** » Sat Feb 14, 2004 8:16 am

> How much does one of these cost and where would I find one?

Jameco has one for $40 on p.78 of their new catalog #241. Their stock number is 76865CA. I had and used one for the same kind of application until it was stolen a couple of years ago. If you have a bigger budget, the little Weller heat gun for $120 (Jameco #191943CA) is much nicer for smaller jobs.

bogax · Post by **bogax** » Sat Feb 14, 2004 7:44 pm

"
How much does one of these cost and where would I find one?
Lyos Gemini Norezel
"

I used a hot air corn popper that cost me a couple bucks at a thrift store.
Took some gimmicking to get it hot enough and/or get the heat
where I wanted it (I made a nozzle out of aluminum foil and covered 3/4
of the air inlets with tape).
I tried some hot air poppers that just didn't seem to want to get hot enough.
I suspect they could have been made to work with a little more effort,
but then I got a hot air gun, so I just never bothered.

The hot air gun that I use now I got at an Ace Hardware for ~$20
Made in China.
Well built and it works good.

bogax · Post by **bogax** » Sat Feb 14, 2004 7:57 pm

Here's a link to a listing on the Ace site:

http://www.acehardware.com/product/inde ... Id=1310859

They list the price at $17.99

bogax · Post by **bogax** » Sat Feb 14, 2004 8:23 pm

I also used a propane torch for a while, but it's much too hard to
control, and much too easy to burn things up.

Some people just use an oven.

One thing I speculated about but never got around to trying,
is using a hot air corn popper or a hair dryer or something as a pre-heater
and then bringing it up to final temperature with a small heat lamp or halogen lamp.
I think that could give you much better control.

When you're depopulating a board, you have to be careful of things
like exploding electrolytic caps.
I also think the preheat/lamp idea might work for soldering surface mounts without
blowing them all over the board.

If anybody wants to try it, I'd love to hear about it

leeeeee · Post by **leeeeee** » Sun Feb 15, 2004 12:28 am

I use a Bosch 1500W hot air paint stripper that cost me 19UKP a few years ago. It came with a set of different nozzles that are very usefull.

For small SM parts I use the very narrow, 12mm, bypassed nozzle (it has a vent on one side) that is ideal for local heating.

For long DIL parts, card edge sockets, SIMM or DIMM sockets I use a flat blade type nozzle. I also use this for IDC pin headers (floppy and IDE ports etc.) and to stop them deforming with the heat plug in a spare cable and use that to pull them out when the solder melts.

For PGA, keyboard, mouse, USB, COM port and similar sockets, I use a narrow, 20mm, nozzle and walk it round and round or back and forth along the pins.

I also keep some copper foil cut-offs handy to fasion heat shields if I want to protect nearby components, this is handy to remove say a BIOS chip from near PCI or ISA sockets.

Other tools used are square bull nosed pliers for pulling DIL parts and most sockets, long thin nosed pliers for lifting SM chips, and a decent bench vice for keeping everything in place. It's also handy to have a metal tray nearby to drop the parts in as you remove them.

Some parts it makes more sense to use a soldering iron to remove, batteries, any through hole electrolytics, sounders and anything that has had the through hole leads bent before soldering.

Practice is the key, and old PC motherboards and cards are ideal practice targets.

Cheers,

Lee.

Lyos Gemini Norezel · Post by **Lyos Gemini Norezel** » Sun Feb 15, 2004 8:32 pm

leeeeee wrote:

I use a Bosch 1500W hot air paint stripper that cost me 19UKP a few years ago. It came with a set of different nozzles that are very usefull. For small SM parts I use the very narrow, 12mm, bypassed nozzle (it has a vent on one side) that is ideal for local heating.

Nice

Quote:

For long DIL parts, card edge sockets, SIMM or DIMM sockets I use a flat blade type nozzle. I also use this for IDC pin headers (floppy and IDE ports etc.) and to stop them deforming with the heat plug in a spare cable and use that to pull them out when the solder melts.

Wouldn't a soldering iron and a strip of braided copper wire (for removing solder) be better for this?

Quote:

For PGA, keyboard, mouse, USB, COM port and similar sockets, I use a narrow, 20mm, nozzle and walk it round and round or back and forth along the pins.

What do you use to remove the solder itself? What you do would only melt the solder... it wouldn't remove it. Do you pull the parts out while the solder is in the liquid state?

Quote:

Other tools used are square bull nosed pliers for pulling DIL parts and most sockets, long thin nosed pliers for lifting SM chips, and a decent bench vice for keeping everything in place. It's also handy to have a metal tray nearby to drop the parts in as you remove them.

Wouldn't a plastic tray be better? After all metal can hold one hell of a static kick.

GARTHWILSON · Post by **GARTHWILSON** » Sun Feb 15, 2004 11:51 pm

If the board has thru-plated holes, there really is no way to get all the solder out of all the holes so the part will drop right out when cold. Solderwick and soldersuckers won't do the job at all. If you want the part to come out in one piece without damage, you pretty much have to have all the pins' temperature above the melting point of solder. That's the issue.

Our company's products' complex boards go up to 12 layers and up to 500 thru-hole parts on a 3.8" x 4.8" board. We achieve such unheard-of densities by putting parts under parts-- like 11 1/8W resistors and diodes staggered in five rows under a 14-pin DIP. On the rare occasion that there's an assembly error and I have to change a part under an IC, I always cut every lead of the IC to remove it, then remove the pins one by one. The price of the replacement IC is nothing compared to the price of the board I could otherwise damage.

I realize in your case however that you're trying to save the IC and not the board. That's where the heat gun comes in. Indeed the board would have to be pretty worthless and the need for parts awfully urgent to go to the effort to remove dirt-cheap pin headers! (I've done it though, when it was the only quick way to get something I should have kept in stock.) If this board you have in mind does not have thru-plated holes though, the disassembly job turns easy.

As for static-- All these CMOS or even NMOS parts we've been talking about should only be handled at a an anti-static work station. It's not necessary to go with the anti-static flooring, the anti-static grounded lab coat, the finger cots, the air ionizer, or even a grounded wrist strap, but you should at least have:

an antistatic mat like Jameco sells, and ground it to one of your pieces of equipment whose chassis is grounded through the third prong on the power plug. The resistance of the mat is low enough to slowly dissipate static, but way too high to let you feel any current going through your body even if you have one arm on the mat and the other comes directly in contact with the power mains. Letting a hot part fall out onto the mat will mar it (my own has many scars) so using a metal tray would be a good move. With everything at the same static potential, you don't have to worry about any ESD damaging parts.
I also used the kind of wire used for DMM probes, and stripped a couple of inches of insulation off one end and wrapped it around the soldering iron heating element right near the handle, and put an alligator clip on the other end to clip to the anti-static mat.
Before you touch anything static-sensitive when you sit down to your work, touch something grounded to discharge any static in your body, and then keep in contact with the mat as you work. This will be almost automatic if you normally wear short sleeves, since at least one bare forearm will normally be on the mat all the time.

I've never damaged anything with static doing things this way. If it's too unnatural to keep some part of your arm or hand in contact with the mat all the time, then maybe you should get the grounded wrist strap too. Altogether we're only talking about a $30 investment here. If you elect to go without it, it doesn't seem to matter how careful you are-- you'll pay the price once in awhile if you work with these parts enough.

leeeeee · Post by **leeeeee** » Mon Feb 16, 2004 12:22 am

GARTHWILSON wrote:

Solderwick and soldersuckers won't do the job at all. If you want the part to come out in one piece without damage, you pretty much have to have all the pins' temperature above the melting point of solder.

That's about the size of it.

GARTHWILSON wrote:

Indeed the board would have to be pretty worthless and the need for parts awfully urgent to go to the effort to remove dirt-cheap pin headers!

Old branded PC motherboards such as Dell, Compaq, Packard Bell etc. that won't fit in anything else and can't be upgraded very far (on board everything types) aren't a whole lot of use. I usually find I have to remove the headers before I can remove the SM parts as I don't like all the melted plastic you get if you try and remove only the SM parts. And, once you get going, it's only a few seconds per part anyway.

Lyos Gemini Norezel wrote:

What do you use to remove the solder itself? What you do would only melt the solder... it wouldn't remove it. Do you pull the parts out while the solder is in the liquid state?

Yes the parts are pulled once all the solder is liquid, any excess is knocked off into a metal bin.

Lyos Gemini Norezel wrote:

Wouldn't a plastic tray be better? After all metal can hold one hell of a static kick.

The trouble with a plastic tray is that the parts can stick to it as they are generally above the melting point of the plastic - messy.

Lee.