MV1C problem with battery

ledfrog

Neo Bubble Buster
Joined
Mar 9, 2017
Posts
42
Yes. No battery connected, but the board is powered on through a super gun that's only providing 5V.
 

cvenditti

Bashful Neophyte
Joined
Sep 25, 2018
Posts
17
I changed PC10 and C3 on my two MV-1C I still have the issue.
Are we sure that C3 is a 0.1uf cap both of the C3 I removed measure 1uf?
 

littlecharlie

New Challenger
Joined
Jan 10, 2018
Posts
27
Well, in my case, I'm going to try and go back to the original setup. I already changed in another mv1c the original battery with a LIR2450 in a socket, and I like this solution (this rechargeable battery maintains power for a long time).

So, back to the failed MV1C base, the problem is that I threw away the components (R36, D5 and D6) so I can`t identify them.
R36 is an 300 ohm resistor, D5 is a diode and D6 a diode zener.
Any idea of the characteristics of D5 and D6 so I can buy them?
Thanks
 

joala

A Joala is for Life., Not Just Christmas.,
Joined
Oct 7, 2017
Posts
644
After some advice, I replaced R36, D5 and D6 with these (from RS Components) just in case my originals were dodgy:

Toshiba 45V 100mA, Diode, 2-Pin SOD-323 1SS357(F)
301Ω 0805 Metal Film SMD Resistor ±0.1% 0.125W - ERA6AEB3010V
KEMET C0805C104K4RACTU 100nF MLCC 16V dc ±10% Tolerance SMD

Still noticing drain. Been using an LIR2477 (about the same capacity as C2032) but eventually the voltage gets too low then would stop charging.

I have a question for James or shadowkn55 - would replacing the backup ram with these work (no battery required)?
https://au.element14.com/cypress-semiconductor/fm1808b-sg/f-ram-non-vol-256kbit-soic-28/dp/2772906
 
Last edited:

shadowkn55

Genbu's Turtle Keeper
Joined
Dec 9, 2006
Posts
2,386
I wouldn't recommend using FRAM as a substitute for SRAM because it has a finite number of accesses before it becomes unusable. Backup ram is accessed far more frequently by the bios for various functions as opposed to a low access memory device like a memory card.
 

joala

A Joala is for Life., Not Just Christmas.,
Joined
Oct 7, 2017
Posts
644
I wouldn't recommend using FRAM as a substitute for SRAM because it has a finite number of accesses before it becomes unusable. Backup ram is accessed far more frequently by the bios for various functions as opposed to a low access memory device like a memory card.

Ok, good tip. Thanks
 

littlecharlie

New Challenger
Joined
Jan 10, 2018
Posts
27
After some advice, I replaced R36, D5 and D6 with these (from RS Components) just in case my originals were dodgy:

Toshiba 45V 100mA, Diode, 2-Pin SOD-323 1SS357(F)
301Ω 0805 Metal Film SMD Resistor ±0.1% 0.125W - ERA6AEB3010V
KEMET C0805C104K4RACTU 100nF MLCC 16V dc ±10% Tolerance SMD

Still noticing drain. Been using an LIR2477 (about the same capacity as C2032) but eventually the voltage gets too low then would stop charging.

I have a question for James or shadowkn55 - would replacing the backup ram with these work (no battery required)?
https://au.element14.com/cypress-semiconductor/fm1808b-sg/f-ram-non-vol-256kbit-soic-28/dp/2772906

I rebuilt my charging circuit, and it is working again, but yes, again draining.
I charge the battery up to 3,2 V, and when I disconnect it, it drains 0.01 V every 5 seconds.
So in less than half an hour, it' s dead.

I have another mv1c which works good, and the battery looses voltage at a decent rate.
So it appears that this problem does not happen to every mv1c.

What I've found is that, without powering the board (only with the battery fully charged), the difference of voltage between +5V and ground (measured in the jamma connector) is 0.25 V. This is extremely weird. And it does not happen with the other mv1c that works properly (difference of voltage is 0V, as it should be).

Can you please check if you too have this small voltage between +5V and ground?
 

joala

A Joala is for Life., Not Just Christmas.,
Joined
Oct 7, 2017
Posts
644
I rebuilt my charging circuit, and it is working again, but yes, again draining.
I charge the battery up to 3,2 V, and when I disconnect it, it drains 0.01 V every 5 seconds.
So in less than half an hour, it' s dead.

I have another mv1c which works good, and the battery looses voltage at a decent rate.
So it appears that this problem does not happen to every mv1c.

What I've found is that, without powering the board (only with the battery fully charged), the difference of voltage between +5V and ground (measured in the jamma connector) is 0.25 V. This is extremely weird. And it does not happen with the other mv1c that works properly (difference of voltage is 0V, as it should be).

Can you please check if you too have this small voltage between +5V and ground?

Hey mate, I think my battery is completely fucked. It drains by about half as soon as I turn the power off. I'll get a new battery and test again.....
 

littlecharlie

New Challenger
Joined
Jan 10, 2018
Posts
27
Hey mate, I think my battery is completely fucked. It drains by about half as soon as I turn the power off. I'll get a new battery and test again.....

OK, keep us informed please. We might find something useful in your problem.

That means the 74HC32 needs to be replaced.
I guess I may have burnt it while doing the battery mod. I'll replace it.
Anyway, can you please explain why you think it is damaged?
 

shadowkn55

Genbu's Turtle Keeper
Joined
Dec 9, 2006
Posts
2,386
I've seen several cases where pins 12 and 13 are outputting voltage even though those pins are inputs. Pins 12 and 13 are connected to the reset circuit which involves a pull-up to the main vcc. Which effectively try to make the backup battery power the entire board.
 

littlecharlie

New Challenger
Joined
Jan 10, 2018
Posts
27
I've seen several cases where pins 12 and 13 are outputting voltage even though those pins are inputs. Pins 12 and 13 are connected to the reset circuit which involves a pull-up to the main vcc. Which effectively try to make the backup battery power the entire board.
If that is the case, we may have found the component that is draining the battery.
 

joala

A Joala is for Life., Not Just Christmas.,
Joined
Oct 7, 2017
Posts
644
I rebuilt my charging circuit, and it is working again, but yes, again draining.
I charge the battery up to 3,2 V, and when I disconnect it, it drains 0.01 V every 5 seconds.
So in less than half an hour, it' s dead.

I have another mv1c which works good, and the battery looses voltage at a decent rate.
So it appears that this problem does not happen to every mv1c.

What I've found is that, without powering the board (only with the battery fully charged), the difference of voltage between +5V and ground (measured in the jamma connector) is 0.25 V. This is extremely weird. And it does not happen with the other mv1c that works properly (difference of voltage is 0V, as it should be).

Can you please check if you too have this small voltage between +5V and ground?

So I got a new battery pack and testing GND and +5v, I see it fluctuate between 0.01-0.03v
 

joala

A Joala is for Life., Not Just Christmas.,
Joined
Oct 7, 2017
Posts
644
OK, keep us informed please. We might find something useful in your problem.


I guess I may have burnt it while doing the battery mod. I'll replace it.
Anyway, can you please explain why you think it is damaged?

Did you try replacing your 74HC32?
 

ledfrog

Neo Bubble Buster
Joined
Mar 9, 2017
Posts
42
Could be a bad diode letting voltage through

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.
 

ledfrog

Neo Bubble Buster
Joined
Mar 9, 2017
Posts
42
Awesome! I didn't think it was that easy. I'm so used to ordering capacitors and having to look up specific values and specs. Thanks.
 

ledfrog

Neo Bubble Buster
Joined
Mar 9, 2017
Posts
42
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.
 
Top