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Reviews Categories | Amplifiers: RF Power - HF & HF+6M | Drake L-4B Help

Reviews Summary for Drake L-4B
Drake L-4B Reviews: 27 Average rating: 4.7/5 MSRP: $995.00
Description: 2000W PEP SSB, 1000W CW
Product is not in production.
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KG4FET Rating: 5/5 Oct 19, 2014 03:37 Send this review to a friend
Hard to beat!  Time owned: 6 to 12 months
RF Deck Built like a tank and plenty of air flow! This is my second 2x3-x00 amplifier. I had a Henry Tempo 2K as well. This L4B is the better amp over all. External power supply keeps that extra heat out of the chassis. Air blowing up through the tube sockets keeps everything cooler so tubes AND sockets will last longer. Keep the blower oiled and free of dust though. No WARC bands? Sure it will. I use mine on 12 and 17m. Use the 10M tap for 12 and the 15M tap for 17M and it will do fine. I don't get quite full power out but it's clean and does well. I have had mine for a year or so and until a few days ago never ran it on the high voltage setting (SSB) and never saw the tubes get that rosey glow. Called a net with it on SSB and it was actually cooler then when run on CW even with the tubes showing "glow". New Pwr supply board in mine and the voltage drop is less then 200 volts at full output on 240VAC. If you can find one and you love that glow of tube gear by all means don't be afraid of this great amplifier, Easier and safer to work on(can disconnect HV supply completely), plenty of info on the net, work horse of an amp, and tubes are cheaper then ceramics.

73 de KG4FET
AD4U Rating: 5/5 Jan 14, 2014 09:41 Send this review to a friend
Great Amp  Time owned: more than 12 months
I bought my L4B in 1973. It still runs the original EIMAC 3-500Z tubes and still puts out 1200 watts with 100 watts drive. IMO the L4B has the best and the heaviest duty RF deck of any HAM amp of that era. The weak spot is the PS.

I recently acquired another L4B RF deck only. I homebrewed a 4KV PS. The only modification to the RF deck was the addition of around 5V of cathode bias to keep idling current around 160mA and tube heat dissipation reasonable. This L4B with the HB PS easily puts out 1500 watts (1900 watts max) on all bands. The original L4B won't do this because the HV is only 2.5KV under load. Since the L4B uses chimneys and a pressurized chassis, the two 3-500Z tubes are adequately cooled even when running 1500 watts output.
N4JHY Rating: 5/5 Jun 19, 2013 07:33 Send this review to a friend
FUN AMPLIFIER  Time owned: more than 12 months
-Back in 1991 I went to the Richmond Frost Fest. Got there early, and had to wait in line till the doors opened. The first table I got to had a Drake L-4b displayed and for sale. I looked down into the top of the perf top cover and just fell in love. This amplifier is just built like a battle ship!
-I have had several amplifiers since, including an Alpha 76PA, that I have now, and I can't sell this L-4b. It is quiet, makes great power 1300-1400 from the original Eimac 3-500z tubes. -This amplifier is what America used to be- great design and building practice.
-If I could have only one amplifier, the L-4B would be it.
-About 3 years ago I treated it to a new set of power supply capacitors, and am sure to every 6 months lube the blower motor. Keeps it nice and very quiet.
-Made a discovery about 2 years ago that I wish to share with all you L-4, L-4B, and L7 owners.
-The high current draw at turn on, that seems to destroy on/off switches, is not from charging the high voltage caps up, but is from inrush current to the tube filaments.
-If you run your amp on 240VAC, look under the RF deck for the 240/120 select terminal strip. If using 240, you are supposed to jumper screw terminals #2 and #3. Remove that jumper and take a pair of GE CL200 inrush protectors (Mouser Electronics) and solder them in series to each other. Then, put that series pair across terminals 2, and 3. They look like disk capacitors, but are black in color.That will remove all that inrush current at start up, and take away that gnarly grown at turn on.
-This is also beneficial to the 3-500z tubes, by limiting the inrush current.
-The filament voltage will be about 5% lower, putting the voltage right about 5.0 instead of 5.2. Your tubes will thank you!!!
-Any questions on this "mod" you can email me for a pic, or what ever info you should need.
-73, Bruce N4JHY "Life is too short for QRP"!!
W5HG Rating: 5/5 Apr 21, 2013 06:56 Send this review to a friend
Its a Great Amp   Time owned: more than 12 months
I've had this amp for 5 years or so now. I was basically the second user of this amp that had not been used for ten or more years. Another operator had inherited it but never used it. When I first looked at it , the amp looked new. I bought it for $600 and figured new caps would be needed fairly soon. I fired it up when I got home and it worked great. It will do about a 1000 watts or better but I drive it with about 65 watts and get around 800 watts. I've used it for around 5 years now and I smelled something burning one night. The next day I turned it on and the Plate voltage was half of what it normally was suppose to be. What I had feared had finally happened. I did some research and bought the power module replacement kit from Harbach Electronics. I also bought the rest of the items they were selling for the L-4B such as the soft start. A good friend of mine did his magic to it and it works like a charm again. The plate voltage is back to a little over 2700. The 3-500z tube is still being sold and easily found. My amp still has the original Eimac tubes. As some of you may know this amp only does 80, 40, 20, 15 and 10 meters. It does not include any of the WARC frequencies but what HF frequencies it does do, it does them well. The Drake L-4B being a amplifier made in the 60's and 70's is a very good looking amp. Very pleased with its looks and performance.
WD9CMD Rating: 5/5 Sep 20, 2012 11:01 Send this review to a friend
A Very Fine Manual Tune Amplifier  Time owned: more than 12 months
One of the best manual tune amplifiers ever made. My L4B was acquired from a SK estate. It has the original Eimac 3-500z tubes and still does 1200-1300w out when driven with a 100w transmitter. When I acquired this amp, it was all in original condition including the power supply. The first thing I did was do a full Harbach upgrade to the power supply. I then proceeded inside the RF deck with a Harbach Soft Key, and a Soft Start. The amp can now be keyed with any modern SS rig. The next step was to change the wiring to operate on my 240v circuit. The last thing to do was to fix the power switch, which was stuck in the ON position. The power switch repair is fully documented on Ron Backer's website, The switch now functions as new.

Normally, I run SSB with the amp on "Low Plate", or in the CW position. Plate voltage in this position is around 1950v per the meter. This relates to an peak reading output of around 1000w with 100w drive. I reduce the drive to about 75w and then have about 700 watts for normal SSB operation. Rarely do I have to push the amp to full output, however its there when needed. Running the amplifier in this mode provides adequate gain for most DX work, and, hopefully, allow the tubes to outlive me.

The one weak point in the amp is the fan. There are no drop in replacements available, and if yours becomes noisey, theres not much to do but make sure you oil the bearings periodically. There are several hams that have modified the amp to work with externally mounted fans. This can be done economically, but does require drilling holes. If the owner wishes to keep the amp original, then there are few options to consider.

In my case my L4B is a bit noisey when first started up, but after about 15 minutes, noise is negligible, and very satisfactory.

At normal used prices, this amplifer is one of the best and most affordable choices available. The amp can also be modified at reasonable cost to operate at legal limit if one so desires. Like most all Drake equipment maded in the 70's and early 80's, its built to last.

73's Dave
W9CMD (formally WD9CMD)
W4DSN Rating: 5/5 Nov 16, 2011 14:58 Send this review to a friend
A Big Boy Amp  Time owned: 3 to 6 months
i bought an L4B that looked like it was rode hard and put away wet. The paint was rough, and the switches stuck. I spent about 2 hours cleaning and un-sticking. The electronics were supreme - new power transformer, Harbach mods, new bottles (tubes to newbies). My ProIII pushes it just right. Does full legal power on all bands, 80 through 10. No 6, no 160. But, the 3-500Z's are not even breathing hard at a full gallon. It loafs along. Plates don't even get rosy.

It is not very agile, you have to re-tune for each band, but it is fast and straight-forward. On-air reports are excellent. I drive it with an IC-756proIII, which has the perfect amount of power. No ALC needed. And, when I get in pile-ups, I get the fastest response and biggest reports of all. They really do not build them like they used to.

L4B's are the only real amps, anything else is just a cheap imitation.
W0KIZ Rating: 5/5 Oct 14, 2011 11:23 Send this review to a friend
Great amp now relatively cheap.  Time owned: more than 12 months
This amplifier is one of the best made. It will put out 1200 to 1300 watts when run on 240 volts. If grid drive is limited to 240 mils and plate current to less than 800 mils, the tubes seem, to last forever. My spare tubes have been sitting on the shelve for over 20 years and have never been needed. Above power measured with a bird digital wattmeter. Switches are the weakest link and should have a relay or solid state relay put inbetween the switches and the line voltage. There is a web site that has information on this modification.
WB0MCO Rating: 5/5 Jul 1, 2011 21:15 Send this review to a friend
Still One OF The Best  Time owned: more than 12 months
I bought mine used several years ago, it need a
overhaul,new tubes,caps and a good cleaning.
It looks and operates like it just came out of the box.
I don't understand the the complaint about the
fan noise,you do have to oil it, mine you can't
hear run. I wish my other amplifier in the shack
was a quite.
Drake must of used two differant manufactured
band switches. The one in my amp is built better
than I've see in most of the amplifiers of today.
I do wish it had 160 meters, I would not had purchased the new amp in the shack.
The L-4B will out last most of them,too bad
RL Drake is out of the amateur radio business.
K2TIS Rating: 5/5 Jan 16, 2011 18:32 Send this review to a friend
A timeless classic  Time owned: more than 12 months
I purchased my L4B new in the mid-60s along with an T4XB and R4B. The only item I still own is the L4B. It ran nearly every day at my QTH in Mexico until I lost my 220 volt service, and I didn't want to run it on the poorly stabilized 110 volt service at my location. It sat in storage until my return to the states. It's been upgraded with new caps, solid state relay, etc. I had one 3-500 go gassy soon after I acquired the unit, but that's all. There are few amplifiers available today that can touch it, and none at its price. If you find one in decent condition, buy it. Even with the cost of upgrades, it's worth every dime.
VE2BBC Rating: 5/5 Dec 19, 2010 08:49 Send this review to a friend
A real delight...!  Time owned: 0 to 3 months
I have the privilege of owning what I consider as the Grand father of the linears... mine has been completely refurbished, Jenning relays fully QSK, step-start, soft-key, power supply has benn recapped....etc etc, so easy to load, very silent...the fan is very quiet and the relays have been placed in rubber grommets so I don't hear them either..sometimes I forget that it's running and it's sitting on the desk 2 feet from me.
Thanks Mr. Drake and Thanks VE2BUB for taking care of my precious amplifier.
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