Console hardware question

[+Vorticon]

Well nuts I managed to flash the final firmaware on my FA18 without any issues, but when I tested it with the console still open and the top metallic shield in place over the motherboard, I got some weird behavior where basically the computer comes up normally for just a few seconds and then I get a loud continuous tone over the speakers and the system locks up. I removed the shield completely with no change. I then broke every cardinal rule of electronics and plugged in my PEB just to see if that changed the behavior (why I would think that is not explainable with common sense discourse...), and now I get nothing at all, even though the power supply is on. Disconnecting the PEB did not change that either. I also noted that the PS was getting very hot within just a few seconds of turning it on, which may or may not be normal behavior.

It sounds like something on the motherboard was shorted by the shield... This is a real bummer because this was my tricked out console with internal 32K and a fast crystal I would really like to try to resurrect it if possible, so if any one here has any pointers for me I would be very grateful.

 

Walid

[matthew180]

The metal shields will definitely float around, so if you are going to power the system with the top one off (and the bottom one on) you should keep the screws in that hold the two halves together. That keeps the bottom half firmly in place so it will not accidentally short something out.

 

Secure your shield and then test the power supply voltages. If those are good, start a visual inspection on the bottom where the shield may have shorted something. Also note that those long white rectangle things on the board actually carry power and ground. I always thought they were just shielding for noise, so I did not hesitate to bend one if it was in my way. Well, one day I broke one off and the console stopped working. So, be careful with those power/ground strips and make sure they are intact.

 

Reseat the GROMs and audio chip, and remove the cartridge bracket (it flops around without the top shield and can cause problems).

[+Vorticon]

I did not know that about these rectangles. I did check them and they seem fine. The power supply is outputting +5V, -5V and +12V - does that sound right?. Now I did notice that the 9918 socket was not getting any power, no did it seem to be connected to ground using a continuity check. Also, the -5V and ground appeared to be shorted together where the PS connector wires connect to the motherboard, again as noted on a continuity check. This is not the case on the power pins of the PS itself. I did a visual check of the motherboard and nothing looked burned out or grossly shorted.

Something really weird is going on here...

[marc.hull]

I did not know that about these rectangles. I did check them and they seem fine. The power supply is outputting +5V, -5V and +12V - does that sound right?. Now I did notice that the 9918 socket was not getting any power, no did it seem to be connected to ground using a continuity check. Also, the -5V and ground appeared to be shorted together where the PS connector wires connect to the motherboard, again as noted on a continuity check. This is not the case on the power pins of the PS itself. I did a visual check of the motherboard and nothing looked burned out or grossly shorted.

Something really weird is going on here...

 

It's almost impossible to check for shorts on the MOBO. Everything is connected to everything and unless your meter is just pegged then there is a chance that you are simply reading back flow somewhere. Not getting powere to the 9918 socket is odd. I imagine you have a data sheet and have the pins correct.

 

It might be one of the wires is either intermittant/off or being shorted out on the 32K16 kit.. Did you cut out the shielding above the daughter board or otherwise insulate it (cardboard?) If a wire is jankey on the crystal switch or return paths that may be it as well. I dread taking my console apart because those little bitty wires are so easy to break and so hard to see. When we improve our consoles we also add in a healthy dose of complexity and a bushel full of mess. It's worth it though .

 

Good luck Walid....

[matthew180]

The event that caused me to realize the white rectangle parts were carrying power and ground was a lack of power to the VDP socket after I broke one off. They are a pain in the ass too, since they are so big, they are like huge heat sinks when you try to solder them. They also carry power AND ground, and the legs sticking out of the bottom will tap power or ground depending.

 

As for -5 shorting to ground, that's bad. It is hard to ohm a motherboard since there are all kinds of paths through the parts, but between any power source and ground, there should never be a path of less than a 1K or so (1K @ 5V == 500ma, which is a *lot* in a situation like this), unless you are dealing with transformers or inductors.

 

The power supply probably has short circuit protection which is saving you right now. Unfortunately isolation is probably the only way to proceed, i.e. remove everything you can that plugs into the motherboard, then start removing parts. That's probably not an option though. I can send you a known working motherboard if you can't get it sorted.

 

[+Vorticon]

Thanks guys. I have an extra console back in MN, and since my wife will be in town this week, I'll ask her to bring it with her. I agree with you Mark, which is why I have been so reluctant to repeatedly open my console to update the FA18, and clearly my fears were justified... My main regret is that I will have to forgo the 32K16 kit modification on that one unless I muster the will to do it again as it was a royal pain to install. The fast crystal modification is much easier, although I doubt I'll do it either because it causes issues with the sprites. Sooo, it's back to the old 32K PEB card, or more likely use my SAMS card instead.

And that's not all! I managed to break a couple of pins on the FA18 after pulling it out one too many times Luckily, that was an easy fix. I just soldered wires to the broken pins pads and connected them to the appropriate pins on the 9918 socket.

 

Perhaps emulators are not such a bad thing after all

[matthew180]

I can send you replacement pins or swap your F18A board all together (which might not be a bad idea since those beta boards do not have the alternate power regulator). Let me know if you need anything.

 

[+Vorticon]

Thanks Matt. Actually, I would like to purchase a new board from you along with a few extra pins if you have any available and keep the old one as a backup. You can send me a PayPal invoice or let me know of any other alternative payment option you prefer.

[matthew180]

You can still pre-order on my store page: http://codehackcreate.com/store

 

Actually boards will start shipping tomorrow, and I'll be cranking them out as fast as I can. I have about 15 ready to go and I'm fulfilling orders according to the purchase date. I'll make sure to include extra pins in your box.

 

[+Vorticon]

You can still pre-order on my store page: http://codehackcreate.com/store

 

Actually boards will start shipping tomorrow, and I'll be cranking them out as fast as I can. I have about 15 ready to go and I'm fulfilling orders according to the purchase date. I'll make sure to include extra pins in your box.

 

Done