Changing TIA on Atari 26000 Jnr

[mamejay]

Hi guys,

 

Just wondering if anyone has every changed a TIA on an Atari Jnr? This is a surface mounted chip which could be a pain. I was wanting to add a socket to the board to make installing the TIA easy.

 

I now have 2 blown ones that I need to change.

I know this as I was doing a AV mod which was working. Then i tested the audio and the sound was all screwed.

I had everything switch off and was checking the TIA. I saw some dry joints and proceeded to reflow them. When I was doing this I saw a spark. You guessed it now I get screwed up colours on the screen.

 

Any help will be appreciated.

 

Thanks Guys.

[Rybags]

Still getting colour so maybe it's not totally screwed.

 

candle did a good guide to desoldering ICs in the 8-bit forum somewhere.

 

 

I've now successfully desoldered a good number of chips from cartridges. The trick is to put the board vertically in a decent vice or otherwise clamp it so you have 2 hands free.

 

I use about 350-370 Degrees C on the soldering iron. Hold the tip against a pin of the IC with one hand, have your solder pump at the ready with the other. Make sure the tip is only putting pressure on the pin, you don't want it pushing into the circuit board.

 

A touch over 10 seconds should get the solder sufficiently hot, keep the iron in place then use the sucker tool from other side of the board. Once will often get it but twice is a good idea. A single pin should therefore be desoldered in a little over 20 seconds.

 

To avoid getting the IC too hot, jump around pins. I find a good idea is to do 1 pin in from a corner, then do the one that's 1 in on the other side.

 

By leaving the corner pins for last ensures the IC won't partially come out which can upset things and/or bend pins.

 

Do the corner ones, but often you'll find that the GND pin is connected to a thick trace which can conduct away the heat and make the solder take much longer to melt.

 

I've just found the best method for that situation is to leave it for last, and use an alternate method. First apply some extra solder to the reverse side, then leave the iron there for a few extra seconds. You want a nice large blob that's maybe 3 times or so bigger than what would normally exist. Then use your sucker tool to get rid of as much as possible.

 

Then go back to heating the pin whilst simultaneously applying leverage with an IC puller, or just use a small precision screwdriver under the chip to lift it.

 

Just be careful - if the chip suddenly pops out you can bend a pin too far and break it.

 

 

During the entire process, you want your soldering iron tinned so that it conducts the heat nicely. It varies, but I found that tinning the iron once was usually sufficient to do at least 50 pins worth of work.

Edited July 7, 2010 by Rybags

[mamejay]

Thanks for the advice. Thats what I needed.

 

How about installing a socket for the new TIA as this is a Jnr which is surface mounted?

[Rybags]

Huh?

 

AFAIK, all the legacy TIAs are DIPs.

 

So you'd just want to solder in your choice of a standard or precision DIP socket.

[roland p]

My father always cut all the wires with a knife, and then desoldered each remaining pin one after another. Assuming the chips are already blown, this could be an option.

[Rybags]

IMO that's more trouble than the normal method for a DIP chip.

 

Cutting pins will usually deform the shape making it harder for them to pull out, plus make getting the solder out harder.

 

The method I used gets most of it away, at best you'd need to quickly go over each hole again using some wick.

 

I used the "destructive" method to get a standard DIP socket out from my 800XL... AFAIK about the only way to do it anyhow, and a right pain compared to the simple removal process for a soldered in chip.

[+batari]

Thanks for the advice. Thats what I needed.

 

How about installing a socket for the new TIA as this is a Jnr which is surface mounted?

It's not surface mount. It's through-hole, and whether socketed or not, it's still through-hole.

[mamejay]

Thanks for the advice. Thats what I needed.

 

How about installing a socket for the new TIA as this is a Jnr which is surface mounted?

It's not surface mount. It's through-hole, and whether socketed or not, it's still through-hole.

Pardon my ignorance.

I am new to the terminology. I am assuming through-hole means it has connections on the top and bottom of the PCB?

 

If so can I socket the thing like on my Atari 6 switch?

[CPUWIZ]

If so can I socket the thing like on my Atari 6 switch?

 

Yes.

[Rybags]

Doing a socket can be tricky. Might be an idea to first make a note of which pins have a trace going from the top side of the board to another location.

 

Then you solder from the bottom side and need to get a good flow in each joint so it contacts both sides.

 

Then check continuity of those top joints with a multimeter and flow in a bit more solder if any aren't done right.

[zylon]

You could also let the socket sit a little high so the top traces can be touched up if needed.

[+batari]

Doing a socket can be tricky. Might be an idea to first make a note of which pins have a trace going from the top side of the board to another location.

 

Then you solder from the bottom side and need to get a good flow in each joint so it contacts both sides.

 

Then check continuity of those top joints with a multimeter and flow in a bit more solder if any aren't done right.

The boards are through-plated so top soldering is not necessary. For that matter, I've seen very few two layer PCBs that weren't through-plated except for homemade or low production boards, or extremely old. A Jr was made in the mid to late 80's so you can basically guarantee through plating.

[A.J. Franzman]

It's not surface mount. It's through-hole, and whether socketed or not, it's still through-hole.

I am assuming through-hole means it has connections on the top and bottom of the PCB?

 

If so can I socket the thing like on my Atari 6 switch?

No, through-hole means that the pins (a.k.a. leads or "legs") of the chip go through holes in the board. Any given pin may or may not have connections on both sides of the board. It's even possible for an entire chip on a through-hole, double-sided board to have all of its circuit connections on only one side of the board.

 

Surface-mount chips are attached to one side of the board without holes for each leg. Also, surface-mount chips are generally smaller than through-hole chips in every dimension, especially thickness and spacing between their leads. There may be other holes in a surface-mount board, called vias, which merely provide electrical paths from one side of the board to the other. Through-hole boards often have vias too, just not as many -- and those that are there may be underneath components, where they aren't easily visible from the top side. Many circuit boards with surface-mount components on them are actually hybrid boards, having a combination of through-hole and surface-mounted parts.

 

The original Atari home videogame consoles predate the widespread use of surface-mount technology and AFAIK all are pure through-hole construction.

 

You can replace a non-socketed chip in a Junior console with a socket and inserted IC, if you don't damage the board too badly when removing the bad part. Pulling a pin out without fully melting the solder, or overheating the board, can result in the copper circuit tracks being broken or peeled up from the board, or even the metal plating inside of the through-holes being pulled out. If this happens, it may become difficult or impossible to make connections from the bottom of the board to the top, underneath the socket being installed, unless the damage is skillfully repaired.

Edited July 8, 2010 by A.J. Franzman

[A.J. Franzman]

Doing a socket can be tricky. Might be an idea to first make a note of which pins have a trace going from the top side of the board to another location.

 

Then you solder from the bottom side and need to get a good flow in each joint so it contacts both sides.

 

Then check continuity of those top joints with a multimeter and flow in a bit more solder if any aren't done right.

But beware of getting too much solder through the hole, if you're not using expensive machined-pin sockets. The cheaper double-wipe (or even single-wipe) sockets can wick solder right up into their contacts, making them solid so that the IC's pin won't go in. If that happens, you might need to completely remove the socket and start all over.

[pags35]

If so can I socket the thing like on my Atari 6 switch?

 

I have done this with a number of Jr's that had bad IC's and it worked great. Like A.J. said just be careful when removing the old IC that you don't damage the circuit tracks. I think I also cut the IC off first so I could remove the pins individually and not cause any damage. I recommend using the individual pins that snap off to whatever length you want them for the socket. Good luck.

[mamejay]

Thanks for the advice guys. I have a bunch of chips coming from Best-Electronics now so I will have fun once they arrive. Anyone know the dimensions of what sockets I need to looks for at my local electronics store?

I have the CD4050 and sockets already so they are covered.

Just need to the TIA, CPU and I/O chips