From: farberbear.unspam@aol.com   
      
   On 8/19/2022 9:08 PM, Phil Allison wrote:   
   >   David Farber wrote:   
   > =============   
   >   
   >> This Schumacher 1042A-PE battery charger stopped functioning today. It   
   >> seemed to work for a little while but when I noticed the car battery's   
   >> voltage wasn't slowly increasing after performing a 2 amp charge for 2   
   >> hours, I checked the voltage at the charger's cables and it was 0 volts.   
   >> The continuity of the switches and cables were all good. I did find a   
   >> power semiconductor which I could not identify, BTW70-200SN. I looked in   
   >> an old ECG cross-reference book and the closest match was for a   
   >> BTW69-800 which is an SCR in a TO-218 package. The package seems to   
   >> match the device I'm looking for. I made some measurements with my   
   >> Simpson 464 DVM on the 2k ohm scale. Pins 1 and 3 measure 38 ohms   
   >> regardless of test lead polarity. All other combinations of continuity   
   >> measure open circuit. In circuit, pins 1 and 2 are soldered together.   
   >> Any idea what this component is or how to test it?   
   >>   
   >   
   > ** Could be an SCR maybe.............   
   >   
   > With a 1A, current limited,  DC supply of about 12 V, + on the anode - on   
   the cathode, apply a brief pulse of +50mA at +1.5V to the gate with - on the   
   cathode as well.  The 12 volt supply should the be clamped at about +1.2V.   
   > You 38 ohm readings are normal.   
   >   
   >   
   > .....  Phil   
   >   
   >   
   >   
   >   
   Questions about the test setup:   
      
   1. For my 1A, current limited, DC supply, I was going to using my bench   
   power supply and set the current limiter to 1A but doesn't there need to   
   be a resistor in series with the power supply in order to prevent the   
   current limiter from tripping?   
      
   2. For the brief pulse, I was going to use a 1.5 volt, AAA battery.   
   Since there's a 38 ohm (internal resistor?) connection between the   
   cathode and gate, does that mean the 1.5 V pulse will be automatically   
   limited to about 40mA?   
      
   3. How do I clamp the 12V supply to +1.2 volts?   
      
   Thanks for your reply.   
   --   
   David Farber   
   Los Osos, CA   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)