x990 McCulloch (Acro) battery pack rebuild problem (LED stays on)

[HummerGuyInFL]

I rebuilt one of my x990 battery packs and now the charging LED remains lit (RED), even when the charger is not attached. I know the battery arrangement is correct since I still have the old battery pack to compare to and it was never disassembled... Voltage is also correct (12v). Any ideas what's going on?

 

[HummerGuyInFL]

i also just finished charging the battery pack and once it reached a full charge, the green LED did come on but the red LED remained lit (turned orange). When I removed the charger the red LED stayed on...

 

[SilverFox]

Hello HummerGuyInFL,

Something isn't hooked up properly. You may want to take it apart and check out what is going on. I have had mine rebuilt without problems, so it can be done.

Tom

 

[HummerGuyInFL]

It's wired correctly... There is really nothing to mess up since the only wires I disconnected were off the battery pack (+ and -). I think there is a bad transistor on the internal circuit board. I'll remove the 3 transistors and test them. I guess it's possible one of them were damaged when the cells ruptured. Hopefully I can find an exact replacement.

 

[HummerGuyInFL]

Can anyone help cross reference these transistors?

Q1 reads: C945 P 21E
Q3 reads: A733 P 19E

 

[Papuga]

Can anyone help cross reference these transistors?

Q1 reads: C945 P 21E
Q3 reads: A733 P 19E

Q1 is a 2SC945 -NPN transistor
Q2 is a 2SA733 - PNP transistor.

Given the complimentary pair, it maybe a push/pull type amplifier or wired as a switch.
Full datasheets are available online, just google the full part number.

I have seen this pair in several different security systems for charging SLA's and the NPN is usually the weaker of the two.

Test using a DMM on diode test and look for 0.6V in the forward direction and open or 1 in reverse. If you get the same reading in both directions the Q is bad. Be sure to check E-C for internal shorts as well

If you need replacements, Mouser or Digi-key are good places to start.

Good luck.

 

[HummerGuyInFL]

Thanks! I pulled the transistors and the A733 PNP transistor was bad... Just ordered a replacement.

 

[HummerGuyInFL]

Transistors were delivered but they're marked:

A733P
W 24

They're suppose to be 2SA733... Are they the right ones?

 

[Papuga]

Transistors were delivered but they're marked:

A733P
W 24

They're suppose to be 2SA733... Are they the right ones?

Don't worry, they are the same. It should work fine as most likely, they are wired in a switch configuration.

Good luck

 

[HummerGuyInFL]

Thanks for your help! Installed and everything is working properly...

P.S. If anyone ever needs one of these transistors just message me. I ended up buying 50 pack for $3 so I have 49 extras; lol.