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--- makita_charger_dc7100 [2015/07/13 16:12] – angelegt karl
+++ makita_charger_dc7100 [2016/11/23 11:42] (aktuell) – dokuwikiadmin
@@ Zeile 5: / Zeile 5: @@
 Here you can find the schematic, if you have to repair this unit.
 {{::makita-dc7100.pdf|}}
+Please see also the blog article from [[http://skyjuiceiswater.blogspot.co.at/2013/11/makita-cordless-power-drill-dc7100.html|Skyjuice]]
+===== How does the Circuit work? =====
+As far as I understand the circuit, the charging current is activated by inserting the battery, raising the minus-terminal, which then triggers through C2 the SCR. The minus-terminal is then at about 0.5-1V. Then the current flows until the thermo switch TS opens.
+Then the minus-terminal rises again (becaus the transformer isn't loaded any more), but now it cannot trigger the SCR, because the TS is still open.
+When it closes again, C2 is allready charged, and the SCR isn't triggered any more, until a re-insertion (whith discharging C2).
+The Zerner is most likly a 2.4V type.
+Then the Gate voltage (= V_R5) is about 0.6V in static state, C2 charged. And this voltage is too low to trigger the SCR.
+So the Zener protects the battery from restarting charging, when TS closes again.
+If you replace it with a 24V type, it has no effect on the charging itself, only on the overcharging protection.