# Sears/Die Hard lead-acid battery charger problem



## Chrysoflux (Jun 3, 2011)

I was wondering if anyone had taken the trouble to make or find a schematic for the control board in the die hard model 200-71222 2/10/50 battery charger. This was a fine charging unit until it got left outside to charge a backhoe overnight. The control board is especially vulnerable as it sits solder side up under the vent slots for the case. A little conformal coating or rubberizing would have gone a long way to making this unit live up to its supposed reputation. Enopugh on thatt. Sears doesn't have a schematic for this board as they just list it as a single part number. Of course its no longer available as a replacement part even though I bought the charger less than two years ago.
I have been slowly making a schematic from tracing the pcb and figuring out the part numbers of the devices used. In fact most of iit is fairly straight forward as the TO-92 devices (6) are either 2N4401 (npn) or 2N4403 (pnp). There are two other semiconductors however, that bear OEM part numbers which appear to have no cross reference or listing in the sources I have access to. 
I do know the main pass device is made by Teccor and the package puts it in the 25 or 40 amp capacity. By its function I'm pretty sure its an SCR as a Triac would be overkill in this application.
There is one other TO-92 packaged device labelled 'R' and I guess I'll have to eventuall say 'this must be a such and such device, judging from the function in the schematic which I have only completed a small part of.
So if any would care to lay some wisdom or perhaps an already drawn schematic on me I'd be suitably wowed.

PS - I'm thinking silicon bilateral switch for the unknown part but that's just a wild guess based on the oem p/n for this 'R' semiconductor. But I could be just fartin and standing downwind of myself.


----------

