I do a compromise. When I repair or upgrade the L4, L4B, or L7 linears, I typically remove the grid grounding chokes, put a 33 ohm 1/2 watt carbon resistor to ground from each grid pin, and leave all of the bypass caps in place. Slightly less drive is required with this configuration plus you still have some protection afforded should there be a plate to grid short. Yes, the 0.82 ohm resistor serves this purpose too but an added measure of protection doesn't hurt. Even though the Eimac literature shows the grids grounded directly, thus requiring less drive, I still feel more comfortable with those resistors in place. To each their own, however.
73, Evan, K9SQG -----Original Message----- From: Jim Shorney <[email protected]> To: [email protected] <[email protected]> Sent: Fri, Apr 1, 2011 11:15 pm Subject: Re: [Drakelist] L-7 Grid Choke value On Fri, 1 Apr 2011 16:55:43 -0500, Lloyd wrote: >I am repairing an L-7 with and open grid choke ( RFC-1 or 3). Does anyone >know the inductance value of these chokes, if so I would sure appreciate letting me what they are. There's a school of thought that suggests that the whole grid choke idea in a 3-500Z circuit is a faulty design decision. I read extensively the comments on both sides of the issue, and decided to remove the chokes and caps, grounding the grids directly to the chassis with copper straps in my L7. I have had no problems to date, the amplifier seems completely stable and tunes up very smoothly. These discussions are out there on the internet, a good search engine should turn up plenty. If you don't get a good answer, I can see if I can measure the ones that I pulled from my L7. 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
_______________________________________________ Drakelist mailing list [email protected] http://mailman.zerobeat.net/mailman/listinfo/drakelist
