RM’s KL505V with PTT Revisited

KL505V face

Having another look at the KL505V with Ptt which arrived from Italy recently. What is so special about the KL505V you may ask? Quite a lot.
I thought I would check it out on RM Italy’s website but it is no longer listed for sale.

Well ..
It is one of our more popular HF Amplifiers as it covers from 3.5 to 30 mhz and pretty much everything in between with quite decent input SWR’s.
Simple…No safety features except fuses (which may or may not work in time to prevent the finals blowing up if you connect the power the wrong way round.)

We asked for PTT to be incorporated into the amplifiers as well as the built in RF switching cos if you want to run data or even CW you want better control of the Amp than RF sensing. Has an RCA jack for the PTT on rear so easy to connect to. kl505v Bottomkl505v back

Don’t forget that are not allowed to use the KL505V on CB. OK? I hope you understand and won’t do it. Triple nickle is OK cos not CB. The Amp does not have any fancy stuff built in to prevent you using it on CB so you have to be disciplined and not do it because it will work very well there I am sure.
You do need to be a little bit careful when you use the KL505V.
Don’t over drive it. !!!!!!
Keep the output under 250w PEP. The manual says 1-10w input on AM/FM/SSB and CW for 300w output. I think 10w input is fine for SSB but I wouldn’t go over 5 or 6 watts carrier on AM/FM and CW.
The manual also says the current draw is 34A max at 12-14 volts DC. There are 3 fuses inside the amplifier. Blow the fuses and your warranty is void because you will rip the warranty sticker to open the case to replace them! I should have checked the fuse value when I had the case open. 12A a piece would make sense. kl505v boardKL505v Finals

The KL505 is a hardy little beast but we just don’t know how good the transistors are inside it. (Cos we don’t really know what they are!)
10 to 12w PEP on SSB will usually see around 250w PEP  out (on the higher bands) and trust me..that’s fine..that’s good..that’s enough. The fans work well and keep it cool. I am sure it will go harder but without any filtering you don’t want to be pushing this too hard or you might just get an award for the Worked all neighbors awards, with credits in toasters, electric organs and stereos! You may not notice it but the audio is starting to compress. I hear stories of people saying they are feeding it with 30w and seeing 375 to 400 out. I am not saying they are full of shit but you will soon need to repair your amp. It is not designed to be used like this.

The KL505V has a 6 position power switch. Low to High. It is not a power switch. It is an attenuator. A portion of your input power is being feed through some resistors to reduce the input power. If possible, reduce the power of your radio to less than 12 watts and run the amp at level 6 with minimal attenuation. Otherwise you are wasting power.
Its got a preamp which I never use cos all it does for me is raise the noise and reduce the intelligibility of the received signal, but there may be cases in a really quiet location and a really bad antenna it may do some good, but I have yet to experience it. The amplifier is just too broad banded for anything like this to be of any use. Leave it off. If I could order them without the preamp; I would.

Because it is simple and without protection it will work in situations where other similar amplifiers (like my Tokyo Hi Power with all the bells and whistles) will shut down due to CMC on the feedline, or RF floating about, or god knows what. And that is why I like it! You just have to be careful, Watch the input, if your antenna is a bit dodgy and the SWR is a bit out of whack; knock the power back and it will keep working. Use it wisely and it will serve you well. Run it flat out for too long and you will probably be looking for 4 new output transistors.

I know of quite a few Hams who are running this amp after their radios with 10w PEP so they don’t have to run their Icom’s flat out. Cheaper to replace the finals in the KL505 than their Icoms they reckoned! They also got 200 + watts out! And… they have been known to forget and run 100w into it and “poof” no more amp! Replacement with a matched set of SD1446/MRF455  and away it went again. Happy camper!

The Finals. They say “SD1446” but they really don’t look like Toshiba’s to me cos they also have RM Italy stamped on them. RM is getting them from somewhere and re-stamping them. Unless They have a special agreement with Toshiba to stamp them? Nope..Mike just told me that Toshiba stopped making them 15 years ago. RM say they are getting these finals made for them. I guess they are using them in all their larger 12 volt HF amps. All the more reason to take things easy with the KL505V. In the accompanying KL505 circuit diagram the final transistors have the numbers blacked out so no information there.  Like all RM Italy stuff the board is well made and neatly laid out. Rev 6.0. I don’t have an original KL500 to compare it to but the KL505V seems a bit beefier with longer fins on the heat sink. And it is black. Stealth.KL505V on box

About David Donaldson

66 and Live in New Zealand now. Hiding from Covid 19! I like to ride my bicycles.
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2 Responses to RM’s KL505V with PTT Revisited

  1. Dan815 says:

    Likely, the finals are made in China by HuaGao (Hg semiconductor) then stamped “RM”. HuaGao also make a decent 2SC2879. Incidently, my KL505v has MS1051 finals (made by Microsemi) which are nearly identical to Toshiba’s 2SC2879.

  2. That’s interesting Dan. Thanks for the info. I must admit that the KL500’s or 505’s..forget which did not do very well. Not sure what the reason was but RM stopped using them and went to 455’s which worked a whole lot better. Had very few issues with the 455’s.

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