4 slot top board problem?

Hine62

Hine62

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Hey guys I have a 4 slot mvs that will boot to hatch screen with just the bottom board. It will also get to the menu for setting the date and such. I don't think the memory can be cleared because the top board is not attached.

The problem is it won't boot to hatch screen when the top board is attached. I get a screen with garbage graphics in squares. I've looked up the calendar error and checked the power to the top board. The power is only 4.3v, is this too low? It should be 5v.

The battery has been removed and I've checked the traces which were fine. Could the 32.768 crystal be dead? But why would the bottom board boot, but not with the top?

Thanks for your help.
Hine62
 
mainman

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You obviously have a short on the top board going by your fault description. There is no easy button solution for this, your going to have to bust out the meter and buzz it out. The only hail Mary advice I can give you is run your hand across the top board powered up and see if any chips get hot.
 
mainman

mainman

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Yes the power should be 5 volts, adjust that right now and see if that helps.

If this method applies to your fault the chip(s) will heat up to the point of being untouchable in 10 to 15 seconds. Be warned you are damaging the board further by powering it up if there is a short. I have used this method twice in the past to quickly fix two 4 slot mobos. Its lazy trouble shooting.

BTW, very important. Which model 4 slot do you have. Hope its not the mini with those custom chips.
 
Hine62

Hine62

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I have the mv-4f.

Checked the voltage and that is good now. Rechecked the traces again and they are all good coming from cn10. I'm thinking (hoping) it's is the crystal, because the calendar screen comes up when booting the bottom board only. It eventually gets to the crosshatch. Unfortunately the electronics store by me didn't have the part i needed. I'm going to try to replace it and see what happens. Might as well try the easiest fix first.

The crystal is a 32.768, can I get one that looks like it or is there a special one I need?

btw... no chips heat up after 10 minutes.
 
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Hine62

Hine62

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ok, here's an update.

After some more searching I found this tread: http://nfggames.com/forum2/index.php?topic=4721.0 , part way down there is a reference to the D4990 clock chip and pin 14 at +5v. I checked this with the top board off it was above 4.5v (the board also gets to cross hatch). With the top board on this pin is only around 3.5v. I think this is causing the problem. 5v is going through the board, but some where the voltage drops. Or...

The PSU I am running this 4-slot on is from a computer. The output is:
+5v / 14A
+12v / 3.5A
-5v / 0.1A

I run a Hyper64 and MV-1 from this same setup with no problems, but will a 4-slot run off this setup?

hine62
 
Xian Xi

Xian Xi

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As been said before, you have a short on the board. Look on the underside of the top board for any pins touching if you can't see anything on the top side.
 
Hine62

Hine62

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I found the problem. It seems that the board is not getting enough power. All +5v lines read +5 coming in, but power drops substantially on the other side of the board and going to the top board. I added more power to the top board through jp1 and it boots normally.

But after hooking up jp1 to add more power to the board, 2 chips uln2803a (9023) heat up. These chips transfer power, so could these this be the problem? And where is the best place to find replacements?

Even with this problem I'm happy it's not something worse. :)
 
Hine62

Hine62

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Bumping this to see if anyone can help.

Here's is the chip that I think is the replacement: uln2803a I have the skills to do this, but just making sure this is the right chip.
 
Hine62

Hine62

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I've installed the two uln2803a chips board works great. They were not hard to replace.

The next problem I have is the left channel sound is softer than the right. I've checked/replaced the slider, but the problem is still present.

It sounds like I'll need to audio recap. How can I tell which 4-slot I have? (I have looked through hardMVS.)

Also has anyone ordered from arcadecomponents.com ?
 
mainman

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Hine62 said:
I've installed the two uln2803a chips board works great. They were not hard to replace.

The next problem I have is the left channel sound is softer than the right. I've checked/replaced the slider, but the problem is still present.

It sounds like I'll need to audio recap. How can I tell which 4-slot I have? (I have looked through hardMVS.)

Also has anyone ordered from arcadecomponents.com ?
Click to expand...

So basically the hail Mary method worked for you this time.

About the audio problem, you simply need to recap the audio section. Does not matter which model MVS board you have with the 1C being the exception when sourcing components for the recap.
 
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Hine62

Hine62

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So basically the hail Mary method worked for you this time.
Click to expand...
It sure did and didn't take long to find. The chip heated up in less than 30sec. :)

Thanks for the reply.
 
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