On Sat, 15 Oct 2011 11:18:48 -0700 (PDT), Ron wrote: >1) Based on pg 126 of the book "A Family Affair - The R L Drake Story", I see >that I should set the current limit trip for ~31 Amp. Does anyone disagree >with this figure?
That matches GW4ALG's notes: http://www.alg.myzen.co.uk/radio/tr7/mods.htm#16 >2) Can anyone explain to me how the 2N4402 bias/conduction works for over >current shutdown of the LM1723? I haven't studied it that much, but here's how it looks like it will work. The current sense part of the 723 senses the voltage across the emitter ballast of one of the pass transistors. When this goes too high, the internal transistor at pins 3 to 13 goes low impedance, which starves the output circuit of the 723 for bias and decreases the output voltage. Pin 4 will always be at a lower voltage than pin 3, since it is farther down on the voltage divider, so when pin 4 falls below the reference voltage on pin 6 far enough, the 4402 (PNP) fires and kills power to the 723 through the 2N3566. I haven't worked it out completely with real world voltages, so I'm guessing a little. I could be missing something somewhere. 73 -Jim -- Ham Radio NU0C Lincoln, Nebraska, U.S.S.A. TR7/RV7/R7A/L7, TR6/RV6, T4XC/R4C/L4B, NCL2000, SB104A, R390A, GT550A/RV550A, HyGain 3750, IBM PS/2 - all vintage, all the time! "Give a man a URL, and he will learn for an hour; teach him to Google, and he will learn for a lifetime." HyGain 3750 User's Group - http://groups.yahoo.com/group/HyGain_3750/ http://incolor.inetnebr.com/jshorney http://www.nebraskaghosts.org _______________________________________________ Drakelist mailing list [email protected] http://mailman.zerobeat.net/mailman/listinfo/drakelist
