Flinnster
Enthusiast
No offence taken, I appreciate the help (and the website resource!) 
PGM charging circuit question
- Thread starter XeD
- Start date
GC8TECH
Grand Master
Thanks, I was worried i did offend you 
Glad that's not the case...
I have 3 new videos i did in just this week, if your interested
Tim.
Glad that's not the case...I have 3 new videos i did in just this week, if your interested
Tim.
chacal231077
Grand Master
Hi!
Can we install an ML2032 and without removing the resistor ?
Can we install an ML2032 and without removing the resistor ?
GC8TECH
Grand Master
Is that a re-chargeable coin cell?? The circuit is built for a NiMH / NiCAD cell. NOT a Lithum or any other battery... So even if you left the resistor... it wouldn't work properly.. and could easily over charge it and make the cell leak.
For me.. i think its easy enough to remove the resistor and just use a non-rechargable coin cell
For me.. i think its easy enough to remove the resistor and just use a non-rechargable coin cell
OlDirty
Student
I have a revision 1 board here and it still looks absolutely clean. Strangely there's a battery holder with a 3032 Battery inside. Looks like the battery holder was soldered in from somone. I have no idea who i bought this from, years ago. Could it be that this mod is correct or should i better remove the battery and live without saving my high scores?
Attachments
GC8TECH
Grand Master
You can see quite a few tracks that has corossion on them. You really should clean that up. It may be even a good idea to remove the battery holder and clen under it as well. Just to make sure.
OlDirty
Student
And then leave the battery completely away? Because i can't use normal baterries like the one which is in now, as i understood.
To resurrect this thread a bit, I also have a revision 1 board that someone worked on before, and had a battery holder installed, and sure enough there's like 4.7 volts across it so the charging circuit was not disabled. What is the proper mod for this revision? This thread mentions both adding a diode and also removing a diode/resistor, I also found a guide linked below which mentions removing both the resistor R24 and a diode D2 (which seems to actually match what's on my rev 1 board).
https://www.jamma-nation-x.com/jammax/tutorials.html#pgmbat
https://www.jamma-nation-x.com/jammax/tutorials.html#pgmbat
Big_P Big_p
Professional
Hey mate I am working on a battery blaster for my PGM similar to the one I made for the MV1c here:
Otherwise just put a diode 1N5817 or 19 between the positive battery terminal and the board to block the charging circuit rather than remove anything.
Otherwise just put a diode 1N5817 or 19 between the positive battery terminal and the board to block the charging circuit rather than remove anything.
GC8TECH
Grand Master
PGM Motherboard Charging Circuit disable.
All you have to do is remove R28 Parts side (REV 8 to REV 12) (REV14 Already has a proper CR2032 from factory. R13 does NOT exsist)
OR R24 on a REV1 to REV 7. Then just fit a normal CR2032 holder where the NI-MH battery was. Simple!
Tim.
All you have to do is remove R28 Parts side (REV 8 to REV 12) (REV14 Already has a proper CR2032 from factory. R13 does NOT exsist)
OR R24 on a REV1 to REV 7. Then just fit a normal CR2032 holder where the NI-MH battery was. Simple!
Tim.
Thanks you both for the answer, I opted for removing R24 since it seems simpler (and well, I don't have that diode at hand), but with the PGM turned on I'm still measuring 2.5V across the battery holder (so lower than before but still not zero), is this expected? Doesn't this indicate that it's still trying to charge it?
GC8TECH
Grand Master
That fine having that voltage there.
Big_P Big_p
Professional
... so, after less than two months of this setup, I can tell it works but not for very long, I already went through 2 coin cell batteries (and I know there's some confusion with bootleg carts not holding the data vs dip switches or bad nvram state, but there's no doubt about it, the battery shows under 1V on the multimeter, it's dead). I'm assuming this is way below what you should expect, how long does it usually last for you? Anything specific to check maybe?
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GC8TECH
Grand Master
The coin cell has no where near the capacity of the original Ni-MH cell. Having said that.. the REV 14 has a coin cell from factory. I think i remember that the Rev 14 only powers 1 chip for the sram saves. But any revision before that powers all 4 chips. That could be why a coin cell doesn't last. Once you remove the resistor. That's all you need to do. Unless the RTC circuit is faulty on your motherboard. The RTC is the only other part that draws power from the coin cell / Ni-MH battery.
Now I found the third coin cell to be dead after around 10 days 
I was checking for the dead battery somewhat infrequently by the way, so I think it's very likely the previous 2 also didn't survive much longer than that...
https://shmups.system11.org/viewtopic.php?p=846242&sid=028b7cf5b884c14aa8884f9eeede16bc#p846242
... and it's 60mAh. Internet tells me that a typical CR2032 should have 235mAh capacity, so it should be better?
Anyway, I kinda don't want to wait at least 10 days again to see what happens, so out of curiosity I thought I'd try to measure the battery draw by putting my cheap multimeter in series:
It seems to measure around 1.8mA when the motherboard is off (it shows 0 when it's on). If we take that 235mAh figure then that's 235/1.8 = 130 hours, so like 5.5 days... who knows what's the true capacity of that battery and this meter isn't the greatest but we're in the right ballpark at least, so I'm somewhat convinced that I didn't just get 3 shit batteries in a row and this really will not survive for very long. If you see a fault in that metodology let me know
I would be curious to see if anyone else with the coin cell mod could try to repeat this? Is this an expected current draw or maybe there really is something faulty somewhere in the battery circuit that causes this? Not gonna lie, if that's the expected result then this solution is just kinda lousy - I can sometimes go more than 2 weeks without powering up my PGM, so there's probably no point in trying to keep my high scores saved
I was checking for the dead battery somewhat infrequently by the way, so I think it's very likely the previous 2 also didn't survive much longer than that...I'm actually not entirely convinced of that, here's someone's original (leaked) battery from shmups forum:
https://shmups.system11.org/viewtopic.php?p=846242&sid=028b7cf5b884c14aa8884f9eeede16bc#p846242
... and it's 60mAh. Internet tells me that a typical CR2032 should have 235mAh capacity, so it should be better?
Anyway, I kinda don't want to wait at least 10 days again to see what happens, so out of curiosity I thought I'd try to measure the battery draw by putting my cheap multimeter in series:
It seems to measure around 1.8mA when the motherboard is off (it shows 0 when it's on). If we take that 235mAh figure then that's 235/1.8 = 130 hours, so like 5.5 days... who knows what's the true capacity of that battery and this meter isn't the greatest but we're in the right ballpark at least, so I'm somewhat convinced that I didn't just get 3 shit batteries in a row and this really will not survive for very long. If you see a fault in that metodology let me know
I would be curious to see if anyone else with the coin cell mod could try to repeat this? Is this an expected current draw or maybe there really is something faulty somewhere in the battery circuit that causes this? Not gonna lie, if that's the expected result then this solution is just kinda lousy - I can sometimes go more than 2 weeks without powering up my PGM, so there's probably no point in trying to keep my high scores saved
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Big_P Big_p
Professional
Can you meter the voltage drop in the battery between when the PGM is first switched off and at 15min, 30min and 1hr. It does indeed sound like a parasitic drain and there are a few things that it could be.
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GC8TECH
Grand Master
The original NI-MH battery is mainly for the "Book Keeping" features in the PGM. Its also made to be in a Arcade like setting. So if the game is powered up from like monday to friday and off during the weekends as an example.. the NI-MH battery would be fine.
There is 2 ideas i'm looking at. One is to use FRAM instead of SRAM so you don't even need a battery at all. Its NOT a drop in replacement.. i have to add some gate logic to it. But i'm working on it. This would be Perfect!
The other option is to check that ONLY the back-up sram chip is being powered (When the PGM is OFF).. and not the other 3 work ram. There is jumpers on the PCB so you can change to configure that. So that's another thing i'm looking at.
As you can guess i have a very busy schedule doing PGM related stuff... So when i have some time... i'll work on it some more.
There is 2 ideas i'm looking at. One is to use FRAM instead of SRAM so you don't even need a battery at all. Its NOT a drop in replacement.. i have to add some gate logic to it. But i'm working on it. This would be Perfect!
The other option is to check that ONLY the back-up sram chip is being powered (When the PGM is OFF).. and not the other 3 work ram. There is jumpers on the PCB so you can change to configure that. So that's another thing i'm looking at.
As you can guess i have a very busy schedule doing PGM related stuff... So when i have some time... i'll work on it some more.
Big_P Big_p
Professional
@GC8TECH are you saying that in your experience that is normal battery consumption?
What about a 1f 5v supercap battery replacement? I have looked at this a little for the MVS but have not gotten around to looking at the charging circuit to see if it's off the 5v or 12v line and if overcharging of the 5v cap is possible or not and I also need to check if there is any reverse leakage from diodes in the circuit that may cause greater capacitor drain than is ideal.
What about a 1f 5v supercap battery replacement? I have looked at this a little for the MVS but have not gotten around to looking at the charging circuit to see if it's off the 5v or 12v line and if overcharging of the 5v cap is possible or not and I also need to check if there is any reverse leakage from diodes in the circuit that may cause greater capacitor drain than is ideal.
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GC8TECH
Grand Master
A super cap would be OK... I did buy a few a while back.. but never tested them at all. The NI-MH battery was charged at around 3.6V
What i need to do is get a REV 14 out.. and do battery testing on that! Since its a factory coin cell setup. I think a rev 14 only powers 1 of the sram.. not all 4 of them with the Ni-MH battery. Again its something i need to look into more.
With all the PGM work i do... My "todo" list is normally larger than i have time to do on it. FRAM will be the best solution.. since you don't even need a battery then...
What i need to do is get a REV 14 out.. and do battery testing on that! Since its a factory coin cell setup. I think a rev 14 only powers 1 of the sram.. not all 4 of them with the Ni-MH battery. Again its something i need to look into more.
With all the PGM work i do... My "todo" list is normally larger than i have time to do on it. FRAM will be the best solution.. since you don't even need a battery then...