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drake l4b

T

troyota

W9WDX Amateur Radio Club Member
May 9, 2007
104
5
28
hello,
i just bought a great looking drake l4b. i was hoping for some pointers on setting it up (tune and load). also what kind of power should i see from this am and ssb? also how should i drive it (how much wattage)? if anyone has a place to download a users manual too it would help. i got the manual with it but it dont tell how to load and tune it. im sure i could figure it out, but thought i would ask here first. thanks for your input.
 

troyota said:
hello,
i just bought a great looking drake l4b. i was hoping for some pointers on setting it up (tune and load). also what kind of power should i see from this am and ssb? also how should i drive it (how much wattage)? if anyone has a place to download a users manual too it would help. i got the manual with it but it dont tell how to load and tune it. im sure i could figure it out, but thought i would ask here first. thanks for your input.
Click to expand...

Pages 9-12 of the manual pretty adequately cover the operation of the amplifier, and the specifications in the front of the manual give you the drive requirements. You say you got the manual with the amplifier, right? That's the only one; there's no "user's manual".
 
Try here;

Manual Display Page

This is the best you're going to find, I think. No idea about printing this out, but that'd be a very good idea.
Best advice is to follow directions! Don't get in a hurry, and don't hold the key down for long periods of time -during- tune up!
I didn't read all of the manual so can't give any specific figures for drive or output. Do not expect anything close to 1kw in AM! Something near a 1/4 of that is almost reasonable, sort of.
And lastly, that thing can make you graveyard dead very easily! Be careful. When they talk about not taking the lid off of it, they are very serious.
- 'Doc
 
thanks for the replys, musta been blind it was right there in the manual..... thanks for the link too.
ok got it hooked up and checked and rechecked all settings. flipped the power switch and a flash ana an arc sound came from one of the tubes.....yea i know not good. switched it off and unplugged it. i could smell it a little. never even put any rf to it. the yellow light came on but the red one didnt. (i think that is the way its supposed to do) seems like its a shorted tube?? sound right? so now about half sick and bummed out too. field day is saturday. was hoping to make some contacts. gonna call the guy in the morning that sold it to me, he said he would guarantee it to be good. i guess i will try out the guarantee. he just lives about an hour and a half away tho.
thanks again for the help.
 
troyota said:
thanks for the replys, musta been blind it was right there in the manual..... thanks for the link too.
ok got it hooked up and checked and rechecked all settings. flipped the power switch and a flash ana an arc sound came from one of the tubes.....yea i know not good. switched it off and unplugged it. i could smell it a little. never even put any rf to it. the yellow light came on but the red one didnt. (i think that is the way its supposed to do) seems like its a shorted tube?? sound right? so now about half sick and bummed out too. field day is saturday. was hoping to make some contacts. gonna call the guy in the morning that sold it to me, he said he would guarantee it to be good. i guess i will try out the guarantee. he just lives about an hour and a half away tho.
thanks again for the help.
Click to expand...

Unfortunately, as you suspect, it sounds as though you had a shorted/gassy tube(s). Glass tubes like the 3-500z do not store well over long periods of time. Did you flip both switches when you turned it on? One is for the amplifier power/filaments, and the other controls the High Voltage. If you only turned on the amplifier it was probably a grid to filament short. However, if you flipped both switches, in addition to the tube you may have blown the protection fuse for the HV (no red light). I believe it is a .82 ohm 2 watt resistor.

Let us know what you find, good luck.

73
 
troyota said:
also what kind of power should i see from this am and ssb? also how should i drive it (how much wattage)?
Click to expand...

A healthy L4B should put out about 1000-1200 watts on SSB, on AM I would not push for anymore than 600 watts peak with 50% duty cycle, 100% modulation, if you want the tubes to have a long happy life. The manual contains all the informaton for output and drive.

73
 
i only turned on the power switch. then it would arc, buzzzz, buzzzz. i could see the plate amperes meter on the front peg out when it would arc. i took the tubes out and checked them. they both looked good. i tried it with the tubes pulled and no problem. then i switched places with the tubes. the arc problem is with one tube only, no matter where i put it.
thanks for the input. i am looking for a tube now....... anyway i have ads on qth and qrz forums looking for one or a pair. i may ad the listing here too.

whoa wait a minute i need to clarify here.
ok when you ask about both switches. the black switch says on /off. the red switch says ssb/ cw tune.
which position should the red swich be in? it was in the cw tune position........so is that what you mean?
thanks
 
another question, could i use a 3-500zg with a 3-500g. im pretty sure that it would work. just checking to see if it would be wise. would it cause trouble or anything?
thanks
 
troyota said:
i only turned on the power switch. then it would arc, buzzzz, buzzzz. i could see the plate amperes meter on the front peg out when it would arc. i took the tubes out and checked them. they both looked good. i tried it with the tubes pulled and no problem. then i switched places with the tubes. the arc problem is with one tube only, no matter where i put it.
thanks for the input. i am looking for a tube now....... anyway i have ads on qth and qrz forums looking for one or a pair. i may ad the listing here too.

whoa wait a minute i need to clarify here.
ok when you ask about both switches. the black switch says on /off. the red switch says ssb/ cw tune.
which position should the red swich be in? it was in the cw tune position........so is that what you mean?
thanks
Click to expand...

Sorry, that was my mistake about the switches :headbang. I don't know what I was thinking, although it has been about 10 years since I've owned an L4-B.

Nevertheless, both lights (yellow and red) should light up (could be a bulb if they don't), read up on the operation of the lights in the manual for the amplifier. The red switch lowers the high voltage level for tuning and when operating CW.

For the 3-500z, I really don't recommend used tubes unless it is someone you trust and know will guarantee them. I know if I am selling used 3-500's I will usually not offer any guarantee, just because they don't store very well. It sounds as though you have a filament to grid short on the one tube.

I highly suggest that if you can swing it, get a pair of the new RF parts branded 3-500ZG tubes from RF parts @$359.00. Or get at least one new one.

Did you contact the guy who sold you the amp? You might be able to cut a deal with him, maybe get him to pay for one half of a new pair of tubes.

The L4-B is a great amp, the RF deck is one of the best ever built. It certainly is worth putting the money into, and yes you can mix the Z and ZG tubes but it is better to run a matched pair.

73 Good luck
 
Last edited:
ok, i got a couple more tubes. i put them in and switched it on and got an arc from the power supply this time. i am getting kinda fed up with this. i changed one tube with the one i had that wasnt arcing and it powered up ok this time, no fireballs. i am getting nothing out of it. when i flip the ssb switch on to get high plate voltage one of the tubes is getting hotter than the other and kinda glows red at the bottom, with no drive (no key.) also i get no clicking sound or relay engagement whatsoever when i key it is perfectly quiet. for now i guess i need to check a few things. power supply being one, what should i look for voltage wise and where? also what do you think about the tube? another bad one? maybe? i know i got way too much in this stinking thing to be dicking around with it.
thanks guys.
 
I don't know if you know this or not but the 3-500 tubes from Eimac are very prone to gassing if left on the shelf very long.Eimac had a problem with the seals and a very high percentage of the 3-500's would leak air into the tubes and cause gassing witch in turn results in arc's and flashovers when high voltage is applied.For this reason NEVER buy used 3-500's.Even if just a year or two old and never used they can be a problem.Constant use generates the heat required to activate the getter in the tube that gets rid of the air molecules that cause the arcing.
 
yep i am aware of that. ok what about the 2 tubes i have that dont arc? one tube getting hotter than the other, and glowing red while the other dont? they do both light up with the warmer. how bout the no relay click or no rf power out issue? you think power supply trouble? i want to see if the thing will work at all before i dump nearly 400.00 in new zg tubes and put in this thing, and maybe kill the new tubes because of another problem. i already have more in this thing than its worth. it would make a great target. i could easily see it from 100-200 yards away. i will be loading my gun shortly... LOL
 
alright more investigation, i am leaning toward the power supply now. i had it turned on idling in a semi dark room and could see a glowing in the power supply it was the resistor (well used to be) that is attached to the ceramic tube. i think it is the .82 that feeds the bleeder. it was destroyed, but still attached. hopefully it hasnt damaged the transformer. it may be in need of an upgrade. i can smell it some too and the top of the power supply gets hot quickly without even flipping the ssb switch on, or tx into it, just in idling mode.
looks like i got a good one huh?
thanks
 
no where in this thread or in any of your posts troyota do you mention any of the following:

1) are you trained to work at high voltage levels? Do you have high voltage gloves? a draining stick? a safe place to work?

2) you are replacing tubes without even testing them. Have you a tube tester or can you get to one? this will tell the truth. You state you "checked" the tubes by pulling them out and looking at them. This is by no means a definitive test. you cant tell by looking at them if they are good or bad.

3) are you really a hamster? If you were (I may be going out on a limb here) but I feel you would be going about this in a totally different manner. (logically)

4) resistors (if sized properly) dont just blow or destroy them selves for no reason. There might be another problem in the amp but you arent taking time or precautions to look for it. You pointed your finger right away to the tubes and then right away again to the power supply. I mean no disrespect but if you point your finger at everything at some point you will by the law of averages point at the problem. Shotgun method is a real tough way to fix something electrical.

5) Do you think you may be happier with an Xforce or a Davemade?
 

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