7800 front panel switches and why they fail

[CrossBow]

This is a topic I would usually reserve as a blog post. But it is pretty important one that effects many many 7800 consoles over their lifetime. So lets talk about it...

The main issue that comes up with the 7800 panel buttons is that over time, they start to fail in that they won't always register a press. The power button and reset seem to be the most problematic and that is likely due to them being used the most. So that is the problem but what is the cause?

Well here is the cause...

The above pictures are the remains and effects of left over flux from the factory when the consoles were manufactured. This one happens to be one of the worst I've seen, but it is crazy common how much I've seen similar. The extra flux is hiding under the switches and over time it can cause corrosion and gunk to build up around the switches and the vias they are attached to. This looks pretty nasty and the switches don't fair any better...

These are the original switches that were removed from the 7800. I did NOT add any additional flux when I removed them. The gunk and wet sheen you seen is the left over flux that has been left for nearly 40 years under those switches. This old flux finds its way into the switches internally and causes them to corrode. As a result, the switches start to loose their contact ability inside them due to this corrosion. 

I've heard of folks taking the switches apart to clean them and then use some super glue to put them back together. But honestly for the time that takes, and as cheap as the switches cost. I don't mess with that, an instead I replace them out whenever I find this. Now to be fair these switches were actually still working properly. But due to other massive amounts of flux that was left over on other parts of the main board, I decided to remove a few to look them over for inspection and once I saw this, I didn't want to take any chances in the future and decided to clean up the mess on the boards and install new higher quality switches. 

You can get OEM style replacements from Console5.com inexpensively here and they would likely serve you well for many years to come:

https://console5.com/store/tactile-switch-12mm-x-4-5mm-atari-7800-power-pause-select-reset.html

The switches I tend to order and use cost 2x more each, but they are a much better quality switch that is rated for 1million cycles of use. That means, the switches you see above are likely to outlive us all. The switches I order I get are made by Alps and use silver contacts internally vs the brass or alum that is likely used in cheaper switches. Because I've found the Alps switches cloned with much crappier versions that look just like them, I only order them from Mouser to be sure I'm getting legit swtiches.

https://www.mouser.com/ProductDetail/Alps-Alpine/SKHCBFA010?qs=4aVxpR%2FL9VKjnfNtzVhXNg%3D%3D

So if you find your 7800 panel buttons not working as good as they should. Just replace them out or find someone you trust that is good with a soldering iron to do it for you.

 

[RickR]

What do you use to get all the extra flux off the board?

 

[CrossBow]

8 minutes ago, RickR said:

What do you use to get all the extra flux off the board?

 

In the case of this one, it was a lot of q-tips an 99.9% IPA. What you don't see and I didn't mention is that the entire board on this 7800 was coated pretty badly with old flux. There were spots of splash from flux in the past. So prior to removing the switches, I actually sprayed the board down liberally with flux remover. But then again I was curious to see the switches because I notice the massive flux buildup under the power LED and I'm glad I did.

I might have missed it or not checked if the owner hadn't requested a different color power LED. But given how much flux was on the board overall prior to my cleaning it, I should have known to check anyway.

 

[DegasElite]

This is an interesting topic. I am sure a lot of A7800 motherboards are like this. Well, fortunately, it's repairable. That's a good thing.

Edited December 12, 2022 by DegasElite

[CrossBow]

On 12/10/2022 at 10:29 AM, DegasElite said:

This is an interesting topic. I am sure a lot of A7800 motherboards are like this. Well, fortunately, it's repairable. That's a good thing.

Oh for sure this is something I've had to do quite often. I always test out the panel switches when working on 7800s. If they test out fine during testing, I usually leave them be. But if even one of them is flaky I will suggest to the owners to go ahead and swap them all out. It isn't that big a deal or expense to do so and it is one less issue to likely have to worry about in the future.

The switches on this one were working quite well and I hadn't planned to replace them out originally. But the rest of the board ha obvious signs of flux splash all over as even some of the main ICs had spots of old flux dried up on them. I cleaned all of that off and didn't think much of it. Wasn't until the power LED was requested to be swapped out for a different color that I saw what my initial cleaning had missed and couldn't get to and decided to look under the power switch to get an idea. Again, I'm glad I did as it really would have only been a matter of time.

The CPU had to be swapped out on that 7800 also and that was actually quite clean under it on the board so my guess is that whatever happened, most of it seem to collect near the front edge of the board.

 

[DegasElite]

Well, at least all hope isn't lost in that respect. It seems like an easy and cheap repair, if one knows what they are doing. Myself, I have no soldering experience, and my A7800s need nothing of this type of repair. But, I would like to learn to solder components onto a motherboard that need replacing. I am sure it takes a lot of patience. One of these days, I might try something like that to learn how to do it. I would take small steps, though.

[CrossBow]

The switches are a good beginner project because it is all through hole and you don't have to worry about aligning them up in any particular way because they will only fit in place really in one way. You don't even have to remove the RF shielding to replace them out although it would be a little squeeze to work around them.

 

[DegasElite]

My concern would be putting too much solder on it. The last time I soldered anything was in high school, and that was 28 years ago. So, I guess I would need practice and tools. I suppose the RF shielding would be no problem because, IIRC, the shielding doesn't go over the switches. That makes sense because it couldn't go over them or they would be blocked from being used by the buttons on the case. It looks like an easier repair anyway.

[CrossBow]

The main concern with replacing the switches is more about using too much heat or leaving the iron on the legs for too long as it could start to melt the plastic inside the switches internally. As for the solder, you only need enough to make a nice little volcano like look on the bottom and although there are 4 pins on each switch. They are a pair that are attached so as long as one of the pins is attached to the trace needed for the switch signal to go through, you are good.