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External CMOS batt.

A

Amigaz

Experienced Member
Joined
Jan 31, 2008
Messages
426
Location
Stockholm, Sweden
I recently aquired an old 386 motherboard which looks pretty much like this one:

http://stason.org/TULARC/pc/motherboards/A/ATLANTIC-COMPUTER-PRODUCTS-INC-386-SER-386C.html

With it came an external CMOS battery with a 4pin connector and one + and one + wire from the battery connected to it like this -+oo

o = empty hole in the connector

The external CMOS batter connector has 4 pins...the first pin is labeled "1" and the last one "4" but I have no clue on to which too pins to connect the battery without frying something...please help me
 
Amigaz said:
Of course but how do I use that on the pins on the motherboard to find out which is ground and positive?
Click to expand...
---
I had the same response, how's that going to help, but if you use the Ohmmeter you could check which pin is ground (-)

m
 
Look at the old battery connector, pin 1 on the cable should have a mark on it like an arrowhead, that connects to pin 1 on the motherboard.
 
Unknown_K said:
Look at the old battery connector, pin 1 on the cable should have a mark on it like an arrowhead, that connects to pin 1 on the motherboard.
Click to expand...

Soryy, but there's no such arrow on the battery cable connector

Hey...nice to see an Amigan here :D

This is a pic I took of the battery connector, sorry for the crap photo...I really suck at taking quality photos

As you see one hole is blocked (white dot)

 
Amigaz said:
Soryy, but there's no such arrow on the battery cable connector

Hey...nice to see an Amigan here :D

This is a pic I took of the battery connector, sorry for the crap photo...I really suck at taking quality photos

As you see one hole is blocked (white dot)

Click to expand...
---
Yeah, connectors with arrows are rare indeed.

If you're sure that's the correct battery, the black wire would probably go to pin4 but I'd still check with an ohmmmeter as I suggested.

Usually, pin1 is + and pin4 is gnd, with pin2 removed. You don't say whether there's provision for an on-board battery, so it may well be that in your case pin3 is used for the positive terminal; make sure there's no continuity between pins 3+4.

m
 
1. Per what Mike stated, the norm is that pins 1 and 4 are the wired ones, as shown at http://members.dodo.com.au/~slappanel555/misc/BATT_2.JPG

2. What is also normal is that the 4 pin external battery connector on the motherboard (J8 in your case) has one of the inner pins removed/cut, and that together with the fact that one of the holes in the battery connector has been plugged (the white peg), means that one can't plug the battery connector the wrong way.

3. Something to be aware of. Some motherboards that have provision for both an on-board battery and an external battery, have a jumper to control which battery is used. I didn't see such a jumper listed on the motherboard layout that you pointed to.
 
modem7 said:
1. Per what Mike stated, the norm is that pins 1 and 4 are the wired ones, as shown at http://members.dodo.com.au/~slappanel555/misc/BATT_2.JPG

2. What is also normal is that the 4 pin external battery connector on the motherboard (J8 in your case) has one of the inner pins removed/cut, and that together with the fact that one of the holes in the battery connector has been plugged (the white peg), means that one can't plug the battery connector the wrong way.

3. Something to be aware of. Some motherboards that have provision for both an on-board battery and an external battery, have a jumper to control which battery is used. I didn't see such a jumper listed on the motherboard layout that you pointed to.
Click to expand...

I'm starting to think that the seller just threw in this battery and it doesn't fir my motherboard since it has 4 pins
The old battery has been removed, the legs are cut off
 
Amigaz said:
Of course but how do I use that on the pins on the motherboard to find out which is ground and positive?
Click to expand...

Hi
I can think of two ways.

1. Turn the computer on. Measure the pins and note the polarity
with the meter. ( assuming the computer is suppose to use
NiCads. If it is suppose to use alkaline cells there is no voltage
on the pins. )

2. With the computer off, locate a TTL DIP part. The pin on the side
with pin 1 that is on the opposite end is ground. Also most machine have
a direct connect of ground to the metal chassis. Measure with the
Ohm meter to determine ground. It should be close to zero ohms.

The black lead on the pack is usually the negative lead. This should
go to ground. Check with meter to match with the computer.

Dwight
 
Dwight Elvey said:
Hi
I can think of two ways.

1. Turn the computer on. Measure the pins and note the polarity
with the meter. ( assuming the computer is suppose to use
NiCads. If it is suppose to use alkaline cells there is no voltage
on the pins. )

2. With the computer off, locate a TTL DIP part. The pin on the side
with pin 1 that is on the opposite end is ground. Also most machine have
a direct connect of ground to the metal chassis. Measure with the
Ohm meter to determine ground. It should be close to zero ohms.

The black lead on the pack is usually the negative lead. This should
go to ground. Check with meter to match with the computer.

Dwight
Click to expand...
-------
Sounds good; an easier-to-find ground is on the center pins of the PS connector.
I think you'd be pretty safe moving the red wire on the connector to the other end, removing the key plug (or bending pin 2 out of the way) and connecting it with red to pin 1 and black to pin 4 (after confirming that pin 4 is indeed ground).

There is usually a diode & resistor to deal with a reversed connection, but I take no reponsibility ;-)

m
 
Hi
Do be careful to match the right type of battery. Most external
batteries use not rechargeable alkalines. These must not be
connected to the charging circuit if a NiCad circuit.
Most of the time, if it is desired to do this, one can remove the
charging resistor that would supply the current for the NiCad
and replace it with a blocking diode.
Dwight
 
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