RL Drake L4-B Amplifier All in One, Soft-Start, Soft-Key, & Bias Module

Description: This RL Drake L4-B module, is fully assembled and is a combination soft-start/soft-key/bias board, specifically for the L4-B amplifier. This all-in-one board limits inrush current during amplifier start-up by placing a small resistive load in series with the AC mains. The load resistor is switched out of the circuit by a relay approximately 2.5 seconds after power-on. It also features a opto-isolated soft-key circuit that reduces the voltage on the keying line to 12 VDC at less than 10 mA current that is also interlocked with the soft-start. The kit also utilizes a string of 10 1N5408 diodes and a 100KΩ resistor to provide DC cutoff bias and user-adjustable idle current biasing. There is also a ready light output on the board for those who wish to use it. The unit mounts on the underside of the RF deck using existing holes in the chassis; no extra holes or modifications to the chassis are required. The board is assembled and comes with all necessary mounting hardware, miscellaneous parts and wiring. The Instruction manual is included. Comments from Jim (VE7RF) sum up the benefits to installing ES4 L4B Paul's ES4L4B superb board is an eloquent solution to a myriad of issues. All solved in one shot. And you can't key the amp, till the 2.5 sec delay has finished. The B+ and fils are both step started, and bias is adjustable. The opto-isolator key line buffer is unique, in that it then eliminates the requirement for the spst mech relay in the yaesu ( and other) xcvr's. The mech relay in the FT-1000D adds another 15 msecs to the mix. IE: Trip vox, 15 msecs for relay in yaseu to close.. then another 15 msecs for 3PDT TR relay in L4B to operate. Meanwhile, TR relay in amp hotswitches. The spst mech relay in the yaesu 1000MP-MKV is just 5 msecs. Same deal...an unnesessary 5 msecs added to the mix..and same hotswitching. With the keying buffer, the SS circuit in either yaesu can be used to interface to the ES4L4B keying buffer. That just eliminated 5/15 msecs of delay. Plus the spst mech relay can be shut off in either yaesu....so the xcvr is totally quiet. ( the yaesu's use pin diode TR setup). I used an opto-isolator as an interface. The yaesu MK-V has an adjustable 0-30 msec delay for the key line.... ( to give the amp a head start).... but that only works for CW, since it buffer's the CW). Doesn't work for SSB. Paul's board does what all my external ..and internal stuff does.... all on one board on bottom side of L4PS supply. Paul's board also eliminates the fubar +130 vdc drake used to bias the amp off on RX....while still retaining the oem ALC function. ( no more burned up center contact of 3pdt tr relay). His board also turns the +26 vdc oem Drake half wave rectifier...into a +26 vdc FWB rectifier. That doubles the +26vdc current capacity. Ok, now it's all set up for a vac TR relay mod, if desired. So no, Drake didn't quite get it right back in 1963. You won't find any amps built these days without step start, none. Jim VE7RF

Price: 89.99 USD

Location: Suamico, Wisconsin

End Time: 2024-03-14T21:43:15.000Z

Shipping Cost: 0 USD