MVS-6 losing system settings and clock running non-stop

mikemann

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So I just got to the end of buttoning up a Neo Candy 25 restore that has a MVS-6 stuffed into it.

I just installed the Unibios 3.2 and switched out the battery to a coin-cell. Removed the 470 ohm resistor.

I'm having an issue with the board losing it's settings on power down and the clock running non-stop. Any ideas what's causing this?

The clock will retain it's settings briefly on a power cycle, but the system settings like enabling game select and turning off attract mode, get reset every time. Also the clock seems to run fine with power on as well, although that might need more confirming

See the video below -



 
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mikemann

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I have done it doing the hardware test menu a+b+c method, but have not done it with all dip switches up.

Is there a preferred method and does it make a difference?
 

Xian Xi

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I have done it doing the hardware test menu a+b+c method, but have not done it with all dip switches up.

Is there a preferred method and does it make a difference?

On some boards the slot for the + side of the battery isn't actually connected to anything but the hole next to it is. You can try bridging them.
 

mikemann

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So just bridge over to the hole where the 470 ohm resistor came out of?

Are my symptoms, typical of like having no battery then? Is that what is happening?
 

Xian Xi

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So just bridge over to the hole where the 470 ohm resistor came out of?

Are my symptoms, typical of like having no battery then? Is that what is happening?

No not there. I just checked and there is no extra hole. I would check to make sure the diode is still good.
 

mikemann

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Just an update for posterity here. I was given some advice from Channelmaniac as well and was told to check the battery voltage and voltage on the ram chips.

So first thing I checked was the voltage of battery, I bought a kit from arcadeaventures for the coincell mod and it came with a new (china-cheapie) CR2032 and I swore I checked the voltage at the time? Maybe not. But in any case it was only ready like 1.7v

So I replaced with a fresh Duracell CR2032. It was reading a tad over 3V out of the package. After install that dropped to ~2.8-2.9V. I also verified I had good continuity across the backside on the pins.

After new battery - Here's what I'm getting on the two backup ram chips on pin 28.





Also for Xian Xi's suggestion, I checked the diode and it appears to be working properly





I'm not sure if the above ram reading is correct? But I put it all back together to test. Had to set date/and soft dip switch setting initially and then powered down. Went to dinner for an hour or so. Came back and it appears to be retaining settings. I'll check again in a few more hours.

It looks like I just had a shitty battery come in that kit. Hoping this fixes me right up.
 

Xian Xi

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Those generic batteries have less capacity than the name brand ones so I'm not surprised. When I sell the kits I only use Sony brand because that's what I use myself.
 

mikemann

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Those generic batteries have less capacity than the name brand ones so I'm not surprised. When I sell the kits I only use Sony brand because that's what I use myself.

Having done this on my MVS-4 about 2 months ago and now this MVS-6. I'm curious how long should I expect the battery to last?

This MVS-6 is crammed into a Neo 25 Candy and it's proving to be a pain in the ass to pull out.
 

Xian Xi

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Having done this on my MVS-4 about 2 months ago and now this MVS-6. I'm curious how long should I expect the battery to last?

This MVS-6 is crammed into a Neo 25 Candy and it's proving to be a pain in the ass to pull out.

It all depends on the draw of the RAM. Some ram only pull a low 1.5 microwatt while some are like 15. I've always had ones that last about 2-3 years.
 

mann0mann

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It all depends on the draw of the RAM. Some ram only pull a low 1.5 microwatt while some are like 15. I've always had ones that last about 2-3 years.

That's cool. Thank you for all the help. I wish I could have bought this kit from you. Totally would have.
 

mikemann

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That's cool. Thank you for all the help. I wish I could have bought this kit from you. Totally would have.

whoops? I'm logging in from work. I didn't realize I created two account here at some point? Maybe someone could kill off the one above?
 

mikemann

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Ok, back to the drawing board...

So the battery replacement was short lived. The Board killed the battery in less than 24 hours. Just got home from work and clock was maxed out, settings gone and pulled the battery to check - dead as could be. zero voltage.

Any other suggestions to check?
 

Xian Xi

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Check the voltage at the board connector to see if it's traveling around the board. Well maybe not at the edge but maybe surrounding ICs.
 

Xian Xi

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I apologize, but I'm not sure I understand how to do that? :(

Check the ICs near the BRAM to see if the backup battery is for some reason powering the rest of the board. If it isn't then check the datasheet for the RAM and it will tell you what the standby draw is.
 

mikemann

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So just a follow up to this. I removed the battery holder and decided to flip it and install it on the bottom of the board. The only thing I did different was use positive lead into the hole on the 470 ohm resistor that I removed.

Essentially following the guide at your sire Xian Xi

I did go through the board and visually try to inspect everything, blow it off a bit with the compressor, etc

After reassembly with a fresh cell, I retained settings for more than 24 hours. I then populated the entire board and waited another 12 hours. All settings retained and voltage on the battery still as new.

So go figure?
 
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