MV1C problem with battery

littlecharlie

New Challenger
Joined
Jan 10, 2018
Posts
27
Did you try replacing your 74HC32?

Not yet. I have the components but haven't got the time to make the replacements (I have never replaced smd components so it doesn't help)
First I'll try the 74HC32 and then the back up RAMs.

Another point is that, out of the 3 mv1c that I have, the 2 in which I added the unibios (with the neobiosmasta) are the ones that drain faster the battery. Will try to find if it is related.
 

BilboBaggins

Twinkle Star Sprite
Joined
Apr 25, 2016
Posts
33
Having a similar problem, but I believe my issue is different. Have a thread here.

4 slot board in a 2 slot cab. Installed coin cell battery and can't get anything to save - high scores, calendar settings etc. I shouldn't have to let it charge since it's coin cell right? How do I diagnose this? Thanks.
 

shadowkn55

Genbu's Turtle Keeper
Joined
Dec 9, 2006
Posts
2,386
Having a similar problem, but I believe my issue is different. Have a thread here.

4 slot board in a 2 slot cab. Installed coin cell battery and can't get anything to save - high scores, calendar settings etc. I shouldn't have to let it charge since it's coin cell right? How do I diagnose this? Thanks.

Did you remove the 470 ohm charging resistor?
 

BilboBaggins

Twinkle Star Sprite
Joined
Apr 25, 2016
Posts
33
Did you remove the 470 ohm charging resistor?

Thanks yes I did do that. I may have installed the battery backwards... :shame:

Going to retry. Curious though - would buying a memory card circumvent the need for the backup ram? Or does a memory card only service high scores / game settings etc.?
 

shadowkn55

Genbu's Turtle Keeper
Joined
Dec 9, 2006
Posts
2,386
Thanks yes I did do that. I may have installed the battery backwards... :shame:

Going to retry. Curious though - would buying a memory card circumvent the need for the backup ram? Or does a memory card only service high scores / game settings etc.?

No. Game settings are only saved in backup ram.
 

jlogo

Timid Neo Newbie
Joined
Jan 31, 2019
Posts
3
Just an update on this in case anyone has the same issue. I ended up finding a radial diode lying around that I installed on my board in the D4 position and my battery draining issue has been completely resolved! Next time I place a parts order, I'll get the proper SMD type, but for now, it's working great. Thanks to all who provided suggestions and ideas.

Hi, could you tell me the specs of the radial diode did you install?
 

ledfrog

Neo Bubble Buster
Joined
Mar 9, 2017
Posts
42
Hi, could you tell me the specs of the radial diode did you install?

Ideally you would want a surface mount diode to make a clean install. I'm not too proficient with diodes, but I assume you just need one that is rated for at least 3.6v. The one I used was bought for a retro Game Boy project I was working on and the model number is: MUR160G. I found it on Mouser and according to the spec sheet, it's rated for 600v. But like I said, this one has leads sticking out, so it doesn't look too pretty the way I installed it!
 

jlogo

Timid Neo Newbie
Joined
Jan 31, 2019
Posts
3
Ideally you would want a surface mount diode to make a clean install. I'm not too proficient with diodes, but I assume you just need one that is rated for at least 3.6v. The one I used was bought for a retro Game Boy project I was working on and the model number is: MUR160G. I found it on Mouser and according to the spec sheet, it's rated for 600v. But like I said, this one has leads sticking out, so it doesn't look too pretty the way I installed it!

Thank you.

I changed the D4 diode for a 1N4004 and everything worked but the the battery leak still was there.

At the end I fixed the battery leak removing C3. after pull out that capacitor the leak was gone.
 

ledfrog

Neo Bubble Buster
Joined
Mar 9, 2017
Posts
42
Thank you.

I changed the D4 diode for a 1N4004 and everything worked but the the battery leak still was there.

At the end I fixed the battery leak removing C3. after pull out that capacitor the leak was gone.

Yeah it seems like this battery circuit has a bunch of different things that can go wrong with it. Hopefully this thread will prove useful for anyone in the future. Glad you got it working.
 

joala

A Joala is for Life., Not Just Christmas.,
Joined
Oct 7, 2017
Posts
644
Finally got around to looking more into this. I think you're right. As a reminder, when my board is powered on, I'm getting 5v on the + battery terminal with no battery inserted. After removing D4, the 5v was no longer present on the empty battery holder so it looks like I've rooted out my problem. Of course now, with D4 removed, the battery is also not able to provide power to the backup ram, so I need some help.

Can anyone report back the exact diode that's supposed to go in D4? I was able to make out "S.4 97" written on it, but I'm not too sure what that means...I don't have much experience with diodes.

I've been having another crack at this and testing out your initial issue and I'm still getting 5v on the + terminal, powered on with no battery even AFTER removing D4 - any ideas what else could be causing the 5v here?

I also tested the rest of the diodes, they're all good but D3 reads voltage in both directions when soldered to the board but when I removed it to test, it only reads in one direction as expected. I swapped it out for a new one and get the same reading....
 
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ledfrog

Neo Bubble Buster
Joined
Mar 9, 2017
Posts
42
I've been having another crack at this and testing out your initial issue and I'm still getting 5v on the + terminal, powered on with no battery even AFTER removing D4 - any ideas what else could be causing the 5v here?

I don't remember if it was mentioned early in this thread or if I read it somewhere else, but I've heard that these boards are multilayered and that this voltage leak could be caused by a short on one of the other layers.
 

Xian Xi

JammaNationX,
Joined
Dec 1, 2005
Posts
27,679
A friend and I eventually nailed down this issue, remove C3 and the two bypass caps on the BRAM. No more parasitic drain. You can replace the bypass caps on the BRAM but they aren't really needed.
 

Beharius

Rugal's Thug
Joined
May 17, 2011
Posts
93
My symptoms are as follows:
I can get around 4-5 volts from the battery terminals when there is no CR2032 battery installed. (Charging circuit disabled)
I also noticed that the 12th and 13th pins of the HC32 outputs around 5volts when the system is running. So it seems I have to replace the HC32 and 0.1uf caps around to solve this issue.
 

Beharius

Rugal's Thug
Joined
May 17, 2011
Posts
93
So I tested the HC32 with TL866 programmer and it's failed. Battery terminal still shows ~5v although HC32 and all the caps removed .

UPDATE : Replacing the D4 diode seems to solve the issue. Thanks to everyone...!
 
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noir

Overtop Pathfinder
Joined
May 23, 2016
Posts
101
A friend and I eventually nailed down this issue, remove C3 and the two bypass caps on the BRAM. No more parasitic drain. You can replace the bypass caps on the BRAM but they aren't really needed.
Are the bypass caps PC2 and PC4 on the top of the board?
 
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