Evening, sorry it has been a long time since I posted on the thread but it took a while to get the parts together and try some things, I have got some charge into the lead acid, so hopefuly if one of you with some understanding of transistor circuits could give me a hand I might be able to fix it...
I have now produced a cct diagram for the board, attached, I have drawn some of the parts pictorially, dotted lines show guess work on my part (I am fairly confident about the relay, calling the orange glass diode a zenner is pure guess work.)
Transistor is now a 2N4401.
Browned resistor is 2.7 Ohm, I have worked out that brown band is in fact a browned gold band and put it back thinking it is just outside tollerance.
As before, when I plug in the correct DC power supply to charge it, the red charge LED lights briefly, then the relay clicks and the red charge LED goes out. The relay remains switched until the DC power is removed, the battery is definately not fully charged.
I have included on the cct diagram voltages measured at various points on the board with the DC supply attached and the relay actuated.
I am guessing that my prime suspect is the orange glass diode, which might or might not be a zenner, can any body work out what the correct spec would be based on the diagram and voltages?
I can't see why the resistor being slightly out would effect things, but as I say I am pretty poor on transistor ccts, if this looks suspect to anybody please let me know and I will change it out.
Would be very grateful for any help, really don't want to be throwing things in landfill,
Kind regards, Craig
P.s. The voltage provided by the other dc charger is not very different from the measured voltage of the one I connected accidently, so that may not have been the cause of the problem...