KLV-550

[bob85]

you will have to use a higher value resistor than 1ohm if you use the zener to drop voltage, its a poor method when you want a bias supply with good load regulation,
you can use a 3 terminal regulator which i have used in 12v amps,

how much current you need for the bias circuit depends on the gain of the outputs and how hard you drive them, a 78xx series reg has proven not to current limit in normal use,

heres how another guy does it on a 12v amp, hes using both diodes to sense the outputs, i prefere one on the outputs and one on the bd179,


http://ad4c.us/RM amps made in italy/KL-500 mods.pdf

 

[liquidh8]

ok, I am looking on newark now to get a regulator for it, the diode is a bad idea then, I guess running a string of diodes like the old tube amps is a bad idea to huh?

I see the LM338, it is an adjustable regulator. the LM38xx you suggested are only 12vdc out, I figured if I do it to 24 then it should be closer to what was original.

Or just use the 12 vdc, and change the 3.3k ohm accordingly. I'll order both and try I guess.

 

[liquidh8]

Tonight I did the regulated 12 volt supply to the bias circuit, moved the diodes back to the heat sink and top of the pills, added you bias fix, and set the bias for about 200ma, working good so far after about 2 hours of talk time on SSB.

Well see if the smoke stays in it, lol.

 

[bob85]

good luck,
if the idle current does not drift too far from 200ma as it heats up and the bias fix is set to turn on just before the antenna relay switches, its working as well as can be expected for that type circuit using random parts,

im changing the fan setup so that both fans run slow in rx and full speed in tx,
also making a small cardboard duct between fans and heatsink so that virtually all the air flows down the fins and off the ends,

sadly, my 30+ years old antex iron stopped working halfway through a rectifier mod and im waiting for a modern replacement, RIP antex:sad:

 

[DIRTYWHITEBOY]

Bob,you need to have a proper burial for that Antex

 

[liquidh8]

I have to set the meter up in there to verify the current staying in check, but, so far I have been rapping on it and getting good report. I have the bias fix in place also.

The duck for the fans sounds like a great idea!

 

[Zman]

My 550 with do about 250-260 on AM and right around 300 SSB. But it sounds like crap on SSB---either it is class C, or mine has some issue with the bias.
I know a few guys on the forums will hate me for saying this but they are all that way. I think they are all biased class C. The two i had both sounded like poopie on SSB so i got rid of them and got a Texas Star 500 and NEVER had any more issues of sounding like poo...

 

[suzerain]

My KLV 550 does about 300W PEP with 4 swing 14 in.
It is only a two pill for gosh sake. And that is good for a 2 pill.

 

[Truck]

I read all nine pages of this threadSoSoundslike a ccouple of you guys are experts on these. Mine will pep at 350w when first fired up but as you talk the wattage immediately starts to fall back and eventually loses close to 100w.the top of the transistors gets cooking hot. Help please

 

[liquidh8]

I wouldn't say I was an expert, just trying to get it sorted out so it sounded good.

I haven't used it in a few months, been talking on my KLV1000 .

Are both or the transistors getting hot when the power drops? are your cooling fans both running while you are keyed up and ragchewing?

 

[redlght]

I know this is an old thread but hoping they guys are still around I have an RM station 550 no KLV on it that sounds horrible on sideband but clean on AM i tried this fix but can not seem to make it sound good on SSB any ideas? This amp does not have R29 and 30 side by side