7800 Voltage Regulator

[Albert]

I just opened up a dead 7800 that is in good physical condition to discover that the voltage regular above the cartridge port snapped clean off the board! The heat sink had also become loose, although it was of course still firmly attached to the regulator. Has anyone ever seen this before? While I fix this I'm also going to replace the power connector with a standard 1/8" mono jack so I can use any 9V 1A adapter.

 

..Al

[Curt Vendel]

Thats rather odd, however if after several years of being knocked around, if the heat sink was not soldered to the PCB at its ends (typically not on the later units) then the weight of the heatsink could've rocks the heatsink back and forth enough times to weaken the 7805 and have it snap off, fortunately Radio does stock them so they are easy to pick up.

 

Make a point of soldering the tips on the heatsink down to the PCB where it sits in the solder through holes... You'll need at least a 40w soldering iron to keep the solder hold enough to bond to the heatsink and pcb as the heatsinks purpose is of course to dissapate heat :-)

 

 

 

Curt

[Albert]

Thats rather odd, however if after several years of being knocked around, if the heat sink was not soldered to the PCB at its ends (typically not on the later units) then the weight of the heatsink could've rocks the heatsink back and forth enough times to weaken the 7805 and have it snap off, fortunately Radio does stock them so they are easy to pick up.

 

Yep, Radio Shack is my first stop, as I also need to see if I can pick up a 1/8" plug I can mount to the rear strut of the 7800. The heat sink is not soldered on this particular 7800, nor on another 7800 I just opened (this one is not working either and I need to troubleshoot it, and it has the 7800 DevOS and AC adapter mods, so I'd like to get it working again..)

 

Make a point of soldering the tips on the heatsink down to the PCB where it sits in the solder through holes...   You'll need at least a 40w soldering iron to keep the solder hold enough to bond to the heatsink and pcb as the heatsinks purpose is of course to dissapate heat :-)

 

Yeah, I'll definitely solder the heat sinks on both of these units down. I'm somewhat surprised they weren't soldered in the first place. Talk about trying to save a penny.

 

..Al

[VidGameKing]

then the weight of the heatsink could've rocks the heatsink back and forth enough times

 

okay, yes I see that as a possibility, but.. who would me jiggiling a 7800 to that point? I just dont see how the motion needed to snap a componet off of a circut board could have been created with a console. Unles maybe the previous owner was moving and he lived on a very rual dirt raod that was ten miles long, and the speed limit was ten miles per hour. It's just a componet snapping off is very weird. Al was the break clean, or did it look like the regulator was blown? maybe like someone stuck 110V ac right into it? that might cause the regulator to short out internally and cause the leads to blow just like a fuse in a car. I would like to see pics, if thats possible. very starnge...

[+Mitch]

I've found a 7800 with the same problem. Pretty uncommon though.

 

By the way, if you're going to do the power mod, use a connector that will fit the Genesis power supply instead of a 2600 power supply. You'll be happy you did.

 

Mitch

[Curt Vendel]

Actually.... go one better, use the same one as the Atari Lynx... MPJA.com sells brand new boxed Lynx power supplies for $2.95 and they are 9VDC 1A so they are perfect.

 

 

 

Curt

[CPUWIZ]

Actually.... go one better, use the same one as the Atari Lynx...   MPJA.com sells brand new boxed Lynx power supplies for $2.95 and they are 9VDC 1A so they are perfect.

 

 

 

Curt

 

That's what I use when I mod 7800's but I switch out the plug as well because they are so tiny.

[Albert]

Well, I replaced the voltage regulator and the 7800 is much happier. Okay, it may not be happier but I'm happier. I also added a 1/8" power jack so I can use 2600 power adapters, which I have a ton of (I also have some generic adapters with 1/8" plugs). Interesting about the Lynx power supply, I didn't know it has the same voltage requirements as the 7800. What size is the Lynx power supply connector?

 

I don't have a stock of Genesis power supplies handy, what type of connector and voltage do they use?

 

..Al

[CPUWIZ]

They are tiny little suckers on the Lynx, as you can see they are too tiny for my taste. LOL

[+Mitch]

I don't have a stock of Genesis power supplies handy, what type of connector and voltage do they use?

 

..Al

 

Perhaps I should have said the Jaguar power supply since this is an Atari forum.

The Genesis 1 and the Jag have the same specs, but I run across Genesis 1 power supplies at practically every thrift and flea market and rarely see the Jag power supply. You, on the other hand, probably have a box full of Jag power supplies.

 

Mitch

[Video]

I imagine that could happen if someone dropped it at the proper angle, but it's still unlikely.

 

It seems most 7800's I've seen, have damaged cases, though they useually still work. Is the case of 7800's just fragile, or am I just unlucky to get ones with broken cases a lot? Out of my 3 current consoles, two have broken cases.

[Albert]

I imagine that could happen if someone dropped it at the proper angle, but it's still unlikely.  

 

This one is in very good physical condition, so I don't think it was dropped, at least not too hard.

 

It seems most 7800's I've seen, have damaged cases, though they useually still work.  Is the case of 7800's just fragile, or am I just unlucky to get ones with broken cases a lot?  Out of my 3 current consoles, two have broken cases.

 

I think Atari used a very cheap plastic to make the 7800 case. I have several 7800s that have damaged cases in some fashion, including one that is just disintegrating on its own. Heck, tonight when I was putting a 7800 back together I broke two of the screw posts when screwing it back together!

 

..Al

[Dustin22mason]

I need some help I did a av mod and replaced all the capacitors and my regulator now my new regulator is smoking help me !!!!!!!

[+-^CrossBow^-]

2 hours ago, Dustin22mason said:

I need some help I did a av mod and replaced all the capacitors and my regulator now my new regulator is smoking help me !!!!!!!

You installed a new regulator, can you give the link to where you bought it and show the solder work on it? My initial guess here is a short on the pins where it was soldered or perhaps on he bottom/top where some of the solder might have crept over and is shorting against one of the other traces as they are so close to each other that it is possible to do.

 

 

[+bent_pin]

Could also be a short with the mod further down the line. Pictures of the top and bottom of all of your solder joints would help.

Did you build the mod or did it arrive assembled?

[Dustin22mason]

I built it 

[Dustin22mason]

I know the fuse or what ever it is but the power plug get hot too the touch too 

[+x=usr(1536)]

2 minutes ago, Dustin22mason said:

I know the fuse or what ever it is but the power plug get hot too the touch too 

There is no fuse in a 7800.

 

Seriously, take (and post) some photos.  It's going to be nigh-on impossible to troubleshoot this without seeing what might have happened with the work that was just done.

[Dustin22mason]

Iv tried too put more soder on the pin but it’s still doing the same thing I can see it the the last pin from left too right but it plays just fine 

[Dustin22mason]

3 hours ago, x=usr(1536) said:

There is no fuse in a 7800.

 

Seriously, take (and post) some photos.  It's going to be nigh-on impossible to troubleshoot this without seeing what might have happened with the work that was just done.

[+x=usr(1536)]

Unfortunately, that doesn't show enough to really go on.  Here's what's needed:

• Photos of all areas that were worked on, front and back
• The type of A/V mod in use, preferably with a link to the instructions you followed
• Any issues that you ran into during installation

Without those, we're just taking shots in the dark.

 

FWIW, I'm seeing what may be a solder bridge on the two resistors (which I think were used in the A/V mod) behind the voltage regulator in your photo.

[+bent_pin]

To get the best pictures, use good lighting, not a flash. Hold your camera a bit further away than you did and use a bit of zoom, as your camera doesn't seem to have a macro focus. Feel free to post too many pictures from too many angles.

[+-^CrossBow^-]

Okay, looks like you are using one of the simple composite only output kits. I can see that you are using a prefabbed PCB by zooming in on the pic you posted.

 

Also, I assume you still have the heatsink being attached to that regulator? Because if not, then the smoking is very likely the thermal compound smoking from the heat of the regulator as it is supposed to be bolted to the large heatsink but it seems yours is removed?

 

Also, I think personally that you might have too much thermal paste on there as it looks like it is also gooped around the regulator legs a bit? Over time, I've see the oils separate out of the paste and become conductive overtime. It would also help to see those solder joints on the legs a bit better to make sure they aren't bridged with each other, or more importantly, bridging on a trace next to them as again, especially on the top, those traces are really close to each other.

 

 

[+Stephen Moss]

Personally I prefer to use thermal pads like this as they are not as messy as heatsink compound and can have better thremal conduction, just make sure you get one for TO220 packages and non-conductive.

On 9/9/2023 at 4:10 PM, Dustin22mason said:

I need some help I did a av mod and replaced all the capacitors and my regulator now my new regulator is smoking help me !!!!!!!

 

On 9/9/2023 at 9:06 PM, Dustin22mason said:

I know the fuse or what ever it is but the power plug get hot too the touch too 

As @-^CrossBow^- stated without a heat sink it could be the thermal compound and there is no issue although I am not sure the regulator would get hot enough for that, also as he said knowing what regulator you used to verify is it suitable would be helpful.

 

However, if we assume for a second that is not the heatsink compond and hte regulator is correct then what are our options...

Again as both @-^CrossBow^- and @bent_pin suggested it is likely to be a short somewhere, a short between the Input and GND pins of the regulator would would make the power unit very hot as it is shorted but not the regulator as ther would be no power running through it, whereas a short on the regulator Output to GND would result in lots of power through the regulator and being drawn from the power unit making both hot.

So if you have a multimeter measure the resistance between the Output and GND pins of the regulator to check for a short circuit, if present...

1. Remove the AV mod, if the short goes away the AV mod or that way you connected it is the issue.
2. If the short is still present with the AV mod removed then visually check every solder joint on the parts you have replaced for a solder short to another component leg (removing any you find). Start with the voltage regulator.

Even if you do not have access to a multimeter you can still apply option 1 & 2 above, the power unit not getting hot would be a good indicator that the problem has been removed, unless you are using a non OEM power unit that has the polarity is reversed. 

[+-^CrossBow^-]

On 9/9/2023 at 6:45 PM, Dustin22mason said:

In looking and thinking about this more, did you order the 7805 from Console5 along with the compound? The white stuff that is sometimes tossed in for free, I've never used as I find it much too runny and use a higher quality compound. Also I can see what I'm pretty sure is the heatsink in the lower right side of this picture? Did you remove the heatsink to take the pic of the regulator then?