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Naomi netDIMM board battery replacement

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big10p View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote big10p Quote  Post ReplyReply Direct Link To This Post Posted: 18 Mar 2017 at 7:02pm
Hmm, something odd is happening...

I read 7.2v on the regulator output terminals, on mains power and battery power, but the voltage I read after the diode goes up to around 9v, when using mains power - how can this be?! Confused Maybe I'm just tired and starting to see things...
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Post Options Post Options   Thanks (0) Thanks(0)   Quote terminator2k2 Quote  Post ReplyReply Direct Link To This Post Posted: 18 Mar 2017 at 10:40pm
Originally posted by big10p big10p wrote:

Hmm, something odd is happening...

I read 7.2v on the regulator output terminals, on mains power and battery power, but the voltage I read after the diode goes up to around 9v, when using mains power - how can this be?! Confused Maybe I'm just tired and starting to see things...

With the naomi powered off is the voltage 7.2v after the diode?

with my chihiro on i get roughly 9v after the diode....powered off it reads 7.2v  , i think this is just the naomi/chihiro charging voltage for the original battery....

if your original battery is ok, remove the new battery/charging system and try putting it back as it was with the original battery  with the naomi on and check the voltage again just to compare.....


Edited by terminator2k2 - 18 Mar 2017 at 10:40pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote obcd Quote  Post ReplyReply Direct Link To This Post Posted: 19 Mar 2017 at 8:10am
It's difficult to compare it with the old battery as that one will charge. So, it will basically form a load on the charging voltage. The new charging system has no load as the diode prevents current from going into that direction. You shouldn't worry about the 9V. It's normal. The voltage of a charged lithium cell can go up to 4.2V. 2 such cells in serie are 8.4V. The 9V is just above that voltage. Their is a small pcb on top of the batteries that has a thermistor to measure the battery temperature and some electronics for BMS and charge control. So, basically, when the batteries are fully charged, the charging voltage is cut off to prevent over charging and damaging the batteries. Also, when their voltage becomes 2 low (fully discharged) they are disconnected to prevent damage of the batterie cells.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote big10p Quote  Post ReplyReply Direct Link To This Post Posted: 19 Mar 2017 at 12:26pm
So, is feeding around 9v into the Naomi OK, then? I tested without plugging into the Naomi and was just surprised to read 9v output when the mains adapter was powering the system, but 7.2v when running on battery power.

I think I must have a fundamental misunderstanding of what's happening. The regulator is outputting a constant 7.2v (whether powered by battery or mains), yet - somehow - the diode seems to up the voltage to around 9v when mains power is used.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote obcd Quote  Post ReplyReply Direct Link To This Post Posted: 19 Mar 2017 at 1:40pm
When the naomi is turned on, it's producing the 9V to charge the battery that was original there. Even if you disconnect the regulator from the dimm board, you will measure 9V on the dimm board connector when the system is on.
The diode is there to prevent that voltage to go to the regulator.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote big10p Quote  Post ReplyReply Direct Link To This Post Posted: 19 Mar 2017 at 2:13pm
Yes, I get that, but I'm getting 9V from the plug that connects to the Naomi DIMM, when it's not plugged into the Naomi (and the Naomi isn't even on). I think I better double check the readings today.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote obcd Quote  Post ReplyReply Direct Link To This Post Posted: 19 Mar 2017 at 5:12pm
Ok. I misunderstood that. So you have 7.2V on one side of the diode and 9V on the other side?
Maybe your meter battery is on it's way out and that is causing wrong readings.
If the diode is placed correctly, you should measure 0.6 - 0.7V lower on it's kathode. So, that should be 7.2 - 0.6 = 6.4V maximum.
To compensate that voltage drop, you might need to set the voltage a little above that 7.2V
 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote big10p Quote  Post ReplyReply Direct Link To This Post Posted: 19 Mar 2017 at 6:17pm
Originally posted by obcd obcd wrote:

Ok. I misunderstood that. So you have 7.2V on one side of the diode and 9V on the other side?
Yes, that's right.

Quote Maybe your meter battery is on it's way out and that is causing wrong readings.
I thought that may be the reason, so replaced the battery with one I found in a drawer, but got the same readings. So, maybe that was flat, too - or my meter is faulty. It's just weird that I only get the high reading when the UPS is being powered by the mains adapter. It reads OK when powered by the battery.

Anyway, I dug out my old meter, and I'm getting the correct/expected readings using that! I'll get a new battery for my 'good' meter and see if that sorts it.

Quote If the diode is placed correctly, you should measure 0.6 - 0.7V lower on it's kathode. So, that should be 7.2 - 0.6 = 6.4V maximum.
To compensate that voltage drop, you might need to set the voltage a little above that 7.2V
I seem to be getting a .4V drop across the diode, but I guess that may be because I'm using a 1N4007, which has a lower rating than the 1N4008?

Cheers!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote obcd Quote  Post ReplyReply Direct Link To This Post Posted: 19 Mar 2017 at 7:27pm
The voltage drop depends upon the current passing trough the diode.
If it's unconnected on one site, it's only the current of your meter that will flow trough it.
On a good diode, it should never exceed 0.8V. The 1N4007 can handle up to 1A. Your meter current is maybe 1 uA.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote big10p Quote  Post ReplyReply Direct Link To This Post Posted: 19 Mar 2017 at 7:45pm
I see. Thanks.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote big10p Quote  Post ReplyReply Direct Link To This Post Posted: 20 Mar 2017 at 8:13pm
OK, I've finally got everything connected up and switched on. All looks good, and no strange readings, now the system is connected and under load. Here's a few pics...

After removing a couple of unused PSUs (for the hopper and hopper controller PCB) from the base board, there was just enough room to fit the UPS system next to the sound amp:


There's a convenient recess in the back of the cab, so I fitted the mains adapter there, making it simple to unplug, if/when I need to shift the cab:


And here it is, installed and working in the cab:


So now (fingers crossed), no more net booting or loss of high scores or ranking tables! Smile

Thanks for all the help, fellas! Thumbs Up
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Post Options Post Options   Thanks (0) Thanks(0)   Quote terminator2k2 Quote  Post ReplyReply Direct Link To This Post Posted: 20 Mar 2017 at 11:44pm
nice job.....i have my ac adapter on a timer plug , and let it charge for 2 hours a day just to make sure its keeping the battery charged up....
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Post Options Post Options   Thanks (0) Thanks(0)   Quote big10p Quote  Post ReplyReply Direct Link To This Post Posted: 20 Mar 2017 at 11:58pm
Originally posted by terminator2k2 terminator2k2 wrote:

nice job.....i have my ac adapter on a timer plug , and let it charge for 2 hours a day just to make sure its keeping the battery charged up....
Yep, I'm doing the same. Smile I figure 2 hours a day should be plenty to keep it topped up.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Rone Quote  Post ReplyReply Direct Link To This Post Posted: 21 Mar 2017 at 6:38am
never seen such a backside style at a sega racing mashine...
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Post Options Post Options   Thanks (0) Thanks(0)   Quote big10p Quote  Post ReplyReply Direct Link To This Post Posted: 21 Mar 2017 at 11:23am
Originally posted by Rone Rone wrote:

never seen such a backside style at a sega racing mashine...
Racing machine? It's a Shootout Pool cashcube cab.
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