RM KL-500 delay on ptt relay

[Broman]

I just bought an rm kl-500, and now i wonder if there is any way to change the delay of the ptt relay?
If i let go off the ptt key, there is 1 second delay before i can hear the station i´m talking with...very annoying!
And it´s almost the same in am mode.
suggestions?

/Broman

 

[Justme]

The KL500 splatterbox has a switch with AM/FM and SSB on it, the only thing that switch does is add a capacitor in the switching line to delay the relay(s) from falling off for a second.
Switching that to the AM/FM you will notice the delay is gone.
If not, someone has been working on the innards...
That is why we hams use a PTT line switched relay(s) for TX/RX, no delays as a R.F. switched PTT line does in these splatterboxes.

You can rebuild the KL 500 easy to be driven from the PTT line of your transceiver if that PTT line is pulled to ground.
Done it here and added a L.P.F to make it a bit cleaner on 10 and changed the Bias for the PA as well.

 

[Broman]

First of all, let me say that I am a beginner, so I hope you understand
Something is fishy with the amplifier, it behaves like this ..
It is almost as lengthy delay on AM as on SSB, a little longer delay in SSB but barely noticeable.
And when I turn on my preamp, tx LED lights and LED preamp and RX will be much worse.
But with the preamp turned on the delay is much shorter, both on AM and SSB.
Hope you understand me because of my bad English ... I'm Swedish

/ Broman

 

[9C1Driver]

Is the amp new or used?

What's your setup, radio, antenna, mobile or base?

 

[Broman]

It is used, and the old version wite white switches on the front.
The radio is a president george, ssb 15w and am/fm set to 5w to the amplifier.
And the antenna is a danish penetrator.

 

[Justme]

# Broman,
Your English is good enough, i'm from the Netherlands, same side of the pond.

In AM/FM the delay should be nothing, the antenna amplifier is fed directly from the + line which should have no influence in the delay time.

Since you have a delay on AM/FM as well someone must have tinkered inside the amp, or might have added a smaller C to get some delay, or just goofed up a repair.
Most of the time the antenna amp transistor gets blown up by wrong connections and gets repaired something might have gone wrong there.
Open up the amp and see if you can find traces of repairs etc.

If you switch in the antenna amplifier does it work and the noise level go up?

 

[Broman]

yes, I also believe that someone has done something with the amplifier.
I'll open it and see if it's something obvious done.
With the preamp on, I lose signal strength.

 

[Tallman]

I have worked on those amps many times, the transistor in the RF-Preamp is susceptible to front end overload. I have replaced those many times.

 

[Justme]

The antenna amplifier should give about 12 to 20 dB gain and noise and signal should go up a lot.
The original transistor can be replaced with a BF199 or equivalent, replaced a few in my repair time, this one is blown up as well by the description of you.
Mostly too much power in or the attenuator switch in wrong position will do that.

Let us know what you find when you looked inside.

 

[Broman]

Do you know where that transistor is placed in the amplifier, I mean the name on it on the circuit board?

 

[Justme]

http://www.rmitaly.com/download/manuals/KL500-manual_rel_300.pdf

Manual and schematic diagram.
Tr 4 is the preamp transistor.
It is the BF199 which is now obsolete but you still can find them if you do a search on the net.

Most people blow them up by putting in too much R.F. or have the power switch in the wrong position when transmitting.

I use a similar transistor in a Shortwave loop amplifier without protection 5 yards away from my inverted L with 1000 watts and it won't blow up.

User mistake in operating the amp will do that.
The only thing the AM/FM or SSb switch does is switching in the 47 microFarad C to lengthen the delay time.
Some ham modifications:
http://www.mods-ham.com/02_Mods/Other-Mods/KL-500/DG2IAQ Modification Sheet KL-500 + PA500UP-817.pdf
Only do the mods if you are an experienced electronics man.

 

[Broman]

Thanks a lot!
It was like this when i bought it...on ebay :angry:
But i´ll be safe with putting in 15w ssb and 5w am/fm in the amplifier?
I will have a look in the amplifier soon, and i´ll be back and tell you guys how it worked out.

Best 73´s/ Broman

 

[Justme]

No problem Broman.
Remember that the KL500 and all other amps from them have a overblown output specified.
Each transistor is rated for 75 watts output less the loss in the combiners etc you should safely get 250-300 wats out of it, use a blower on it to keep it cool.

The design is actually quite old and can be found in the old Motorola transistor handbooks i have in the EB ( engineering bulletins)

Driving the amp too far will result in lots of problems but keeping it at the levels of 250-300 watts will keep it relative clean and long lasting.
Remeber for one S pont more you need 6 dB extra or 4 times as much power.
Going from 300 to 400 watts is not noticable on the other end.

Running the 200 watt FT 2000 - D here i gain just 1 S point running 1000 watts here from the Heathkit SB-1000 tube amp.

Going from 5/5 watt to 250-300 watts in your casee will give more results, but don't push the amplifier too much.
That will make sure it will last you a long time.
Good luck repairing it.
Cor

 

[Broman]

I have replaced the transistor Tr4, and the preamp works great.
And the delay is much shorter, so the amplifier is working properly now.
Thanks for the help guys!

/Broman

 

[Justme]

Congrats!
Good to see you got things sorted now, have fun using it.