Bacteria's Multi-Platfrm project - Phase 2 - SNES

bacteria · Post by **bacteria** » Wed Jul 23, 2008 2:05 am

This is nuts - freshly charged batteries, same problem. Hooked up a wire to the 5v output on the 7805 and another to ground, connected them to my multimeter - constant 4.99v, yet system still died after only about 4 minutes runtime.

Changed the video to composite instead of RGB - incidentally, surprisingly the picture quality on the PSone screen was exactly the same, after all that messing about; so decided to keep output as composite after all - no visible benefit with RGB (surprising). I thought the resistor on the composite line (for the C-sync) was possibly the issue, but isn't. System still cut out after a few minutes.

Decided therefore the issue wasn't with the voltage, batteries or video signal - only one plausible thing left - heat from the 7805 itself. On the back of the SNES case it stated the system used 1.3amps, which after all is about 4-5 times the amps your American mini-SNES's seem to need = more heat.

Just ran the system for 30 mins with a fan blowing air around the 7805 before it cut out. This is far better than before, but still sucks. I will try a TI card instead at 5v, remove the 7805 and pump 5v directly into the board from the TI card. That should hopefully eliminate the problem once and for all. Will keep you posted.

bacteria · Post by **bacteria** » Wed Jul 23, 2008 4:15 am

Found if I used a 0.32Kohm resistor I got 5.04v output from a TI card. Got that rigged in the system but it didn't boot. Guess the SNES needed more than the TI card could give it.

Pic of system running (ignore the elastic band, holding the game cart in place):

Ok, no idea what the issue is, might be something damaged when experimenting with the RGB, as I did try a few things out initially which weren't successful. Voltage is fine and stable, controls work fine, i'm no longer of the view that the heat from the 7805 is the issue in itself as although it gets warm it doesn't get really hot. I tried a proper 7805 heatsink and even bolted the 7805 onto a piece of flat steel and had a fan blowing directly onto it.

I can only think that the SNES board is defective or damaged; in which case I will have to rip apart another SNES and try that one out (good thing I have a few!). They are old boards after all and you can get dry joints, etc.

Before I change the mobo for another one, anyone got any bright ideas as to why I have been getting cutouts?

I even put on the original capacitor, made no difference. It is strange as normally a fault means you can't get the system to work or it behaves strangely; not that it works perfectly then just goes off!!

Update - The more I think about it the more I think the SNES board might have a problem. Just for an acid test, I have been running Pokemon Puzzle League on the N64 in my system for over two and a half hours non stop now; (the noises it makes going through the intro loop gets annoying rather quickly I add "way to go", etc). Proves my system is fine and i'm not getting any resets from the system itself (thank goodness).

No more time today and won't get much time over next days, but I have to get this problem resolved before I can start the compo. I don't like having multiple projects on the go at the same time!

I will take the opportunity to try and make the SNES system more streamlined if I can.

GonzoMPM-1 · Post by **GonzoMPM-1** » Wed Jul 23, 2008 9:31 am

Bacteria:

It has been my sorry experience that not all 780X chips are created equal.

Its seems possible you've got one on an extreme side of things, such that the drop out is high, and therefore when your batteries get only ever so slightly below 5v + "X" it cuts out.

I'd try for a different 780x or even look to a switching regulator as a substitute before canning the MOBO.

If there were more systemic power problems aside from a drop out in your supply circuits, the system would not be functional at all.

Oh, and the video circuits are well enough isolated from everything else that I cannot imagine any tinkering there bricking the rest of the board, at least not on what you've described.

bacteria · Post by **bacteria** » Wed Jul 23, 2008 3:18 pm

Thanks GonzoMPM-1 for the comment. I did try a different 7805 earlier and got similar results. No idea what it refers to but the 7805 from the SNES was a 17805S and the one I then tried was a DE7805 - same result. They certainly get warm quite quickly (couple of minutes or so). I guess either the problem is that the 7805 is getting too hot and cutting out (but then why isn't it consistent rather than 4 minutes one time, maybe 30 mins next time?) or as you say, a slight drop - however I did a test on this earlier by wiring my multimeter to the system, it gave a constant 4.99v lowest 4.98v; even at a constant 4.99v the system cut out.

For interest, ran my N64 section on the screen/control system, got 6 hours continuous use before the batteries died. Thought it would be good to see how long they last.

I tried a TI card with a small resistor, outputting 5.04v, removed the 7805 and wired directly to the output wire of the 7805 pins; nothing happened, system wouldn't boot. Thinking about it, perhaps I should try this again but this time with the 7805 in place and wire the 5.04v directly to the output pin of the 7805?

I would like you guys to comment please with suggestions - it would save me a fair bit of work to get my existing system working rather than hack up another board!

GonzoMPM-1 · Post by **GonzoMPM-1** » Wed Jul 23, 2008 4:31 pm

bacteria wrote:Thanks GonzoMPM-1 for the comment. I did try a different 7805 earlier and got similar results. No idea what it refers to but the 7805 from the SNES was a 17805S and the one I then tried was a DE7805 - same result. They certainly get warm quite quickly (couple of minutes or so). I guess either the problem is that the 7805 is getting too hot and cutting out (but then why isn't it consistent rather than 4 minutes one time, maybe 30 mins next time?) or as you say, a slight drop - however I did a test on this earlier by wiring my multimeter to the system, it gave a constant 4.99v lowest 4.98v; even at a constant 4.99v the system cut out.

For interest, ran my N64 section on the screen/control system, got 6 hours continuous use before the batteries died. Thought it would be good to see how long they last.

I tried a TI card with a small resistor, outputting 5.04v, removed the 7805 and wired directly to the output wire of the 7805 pins; nothing happened, system wouldn't boot. Thinking about it, perhaps I should try this again but this time with the 7805 in place and wire the 5.04v directly to the output pin of the 7805?

I would like you guys to comment please with suggestions - it would save me a fair bit of work to get my existing system working rather than hack up another board!

Have you measured the voltage coming off your batteries and into the 7805 when the system cuts out?

Also, have you inserted your multimeter between the 7805 Vout pin and the load and measured current draw?

This is all very odd.

bacteria · Post by **bacteria** » Wed Jul 23, 2008 10:14 pm

GonzoMPM-1 wrote:Have you measured the voltage coming off your batteries and into the 7805 when the system cuts out?

Yes, exactly the same;as mentioned, 4.99v even at cutout.

GonzoMPM-1 wrote:Also, have you inserted your multimeter between the 7805 Vout pin and the load and measured current draw?

This is all very odd.

Not sure where to measure the load; although don't see how that would be the issue as the original part was designed to work in the original SNES.

Yes, it is very odd.

Valium · Post by **Valium** » Wed Jul 23, 2008 10:34 pm

You ought a try running another Snes off your batteries. If the problem occurs again, then you know there's nothing wrong with your Snes board. If it doesn't, then you've got some work to do.

bacteria · Post by **bacteria** » Thu Jul 24, 2008 2:04 pm

Valium wrote:You ought a try running another Snes off your batteries. If the problem occurs again, then you know there's nothing wrong with your Snes board. If it doesn't, then you've got some work to do.

Indeed.

I will:

i) run a SNES off batteries (no other mod than connecting batteries to the voltage in on the 7805 and ground to ground); see if that works reliably for an hour plus.

ii) if it does, take off the bottom metal plate off, again see if runs for 1 hour plus.

iii) remove the metal plate off the 7805 and put in a heatsink, again test for an hour plus.

iv) if get to this stage iv), I know the first mobo I used is faulty and will replace with the one used above; if stuck on iii) may need to retain metal plate.

Trick is to experiment a bit at a time until the fault is identified; then the issue can be cured.

bacteria · Post by **bacteria** » Fri Jul 25, 2008 12:57 pm

Think I may have solved the issue.

Opened up a SNES which didn't want to play many games (connections might not be good, working on logic that I am bypassing the pins anyway as I am soldering directly to the board contacts.

Attached 7.4v to the Vin of the 7805 and soldered the negative to the grounding on the SNES mobo. Left for an hour and a half, working perfectly.

Removed the other metal heat plate and ran system for best part of an hour.

Dremelled off at the top edge of the metal heat plate on the main bit, with the 7805, so there is still plenty of metal attached (the plate was barely even vaguely warm after the system was on for over an hour); removed the SNES from the casing; took off the power switch (redundant when wiring straight to the 7805), back on again.

One big difference to before, noticed that the LED to show the system is on is on this time on the other system (in my project) the LED is off. (?).

I rather think the old SNES mobo I was using was entirely at fault; am not getting heat issues.

I will be able to level down the board and relocate the cart slot Monday morning and replace the existing one in the case with it.

bacteria · Post by **bacteria** » Wed Jul 30, 2008 9:58 am

Ok, new SNES board works, had it running for a while; then proceeded to remove the ports, relocate the cart slot, remove the antenna TV output, etc. Ran system again in this state for over an hour, all great.

I have now wired it back into the system and disposed of the old SNES board. It is currently on test, has been for over 2 hours 15 mins now, working great. This one is fine!!

:

Jobs left to do:

* Make casing.

* Work out how to make cart slot secure to the casing, as using a non-standard female connector.

eurddrue · Post by **eurddrue** » Fri Oct 24, 2008 9:29 pm

ShockSlayer wrote:Although I already know that this thread will always be at the top of the forum and will probably span 15 pages of just your updates, I can clearly see that this one will happen quite fast.

So far we know that you rmoved the case and have begun flattening it. Looks good so far, I mean, its not like I havent seen a naked snes before.

SS

I think you are wrong

I had to scroll down, this was the second to last thread...

I just wanted to check in on you multi-platform, and see how this is going

bacteria · Post by **bacteria** » Sat Oct 25, 2008 2:58 am

The system was working and complete when I left it on my last posting, solved the issue with the 7805 and got a few hours playtime on the batteries. Just needs the casing to be finished.

I got diverted from finishing, with the compo in August; will finish this, after doing a couple of other projects first (with vacuum forming), PS1 and N64 again.

I will complete this, and do more systems, have no thoughts otherwise!

Nicholas64 · Post by **Nicholas64** » Thu Nov 06, 2008 6:23 pm

You know bacteria, i couldn't helpt notice your mobo was a bit different from mine, but i think we have the same Snes. Did you modify it? And no i not talking about the capacitor, and the removings you made, i just noticed a bit of differences.

Tibia · Post by **Tibia** » Thu Nov 06, 2008 7:39 pm

Bacteria's got a PAL SNES. He's in Britain, so things are slightly different for him.

bacteria · Post by **bacteria** » Thu Nov 06, 2008 8:40 pm

Indeed, PAL is a pain because most of the world uses NTSC. Some systems, like the small Genesis aren't available in the UK, nor the small SNES.

Had to buy an NTSC PSone screen for a Retro Duo (waiting for both to arrive) as the Duo needs an NTSC screen (although it plays PAL games); got a second NTSC PSone screen won yesterday also on e-bay with 9 PS1 games (NTSC) and NTSC PSone console and 2 controllers for Â£32 shipped. Good price. Have an idea for a project for the second screen - or may take a commission for an NTSC PS1 system, not sure yet.