KL 503 seems to work fine but!!!

[Buffalo]

Let me see if I can remember exactly what happened today. I know I will catch some flack but I’m driving it with a Q5N2. The weird thing that is happening is when I have the amp switched to SSB no TX indicator light comes on. And I can’t hear any relays. But, great audio reports with some long QSOs on side band today. On level 3, which is as high as I will go, because my MFJ meter is only 300W max, I get a clean 250 W PEP. Radio set at 10W PEP. Didn’t have enough to even key the amp with radio power turned all the way down. Nothing even came close to getting hot or even really warm. Even after a long winded contact on FM which I was only on level 2 with a 175W carrier. Just wondering if I should have any concerns with no tx light above the ssb switch and not hearing the relays at all? All seems to be working great except for that.

 

[ForestRunner98]

First off…nice radio!! I am running a McKinley w/ a 503. With it’s power turned all the way down it will not key the amp. That’s on AM. I keep the radio power up on SSB (12w PEP) But on SSB the amp light won’t come on even when keyed if I don’t modulate it. Once I speak, the amp light comes on like it should.

175w carrier seems high. Your Q5 could be a little hot for the 503. I run my amp on level 5 and on AM it’s at a 60 or so watts carrier and it swings to around 350w.

In all it seems like your amp is working like it should. Your MFJ reads PEP I assume?

 

[Eldorado828]

I agree with @ForestRunner98 , seems your kl503 is working like it should but it won't last long with that radio.
We've already seen and forum member suffer a casualty running your exact same combo. He reported great results too but it didn't last long before the issues started. The end result was a cooked amplifier and a radio with bad ssb audio.

Too much POWA for that amp and it's only a matter of time.

 

[Buffalo]

First off…nice radio!! I am running a McKinley w/ a 503. With it’s power turned all the way down it will not key the amp. That’s on AM. I keep the radio power up on SSB (12w PEP) But on SSB the amp light won’t come on even when keyed if I don’t modulate it. Once I speak, the amp light comes on like it should.

175w carrier seems high. Your Q5 could be a little hot for the 503. I run my amp on level 5 and on AM it’s at a 60 or so watts carrier and it swings to around 350w.

In all it seems like your amp is working like it should. Your MFJ reads PEP I assume?

Yes my MFJ reads peak and average. FWIW!!! The 175W carrier I was referring to was on FM where I have the radio set at I believe 4W output. Thanks for the reply!!

Eldorado you are probably correct but I think the biggest threat is going to be from operator error. Theoretically the radio can be set not to overdrive anything. But can be and will be are two different things all together. Especially with different radio output settings per mode.

 

[TimmyTheTorch]

I agree with @ForestRunner98 , seems your kl503 is working like it should but it won't last long with that radio.
We've already seen and forum member suffer a casualty running your exact same combo. He reported great results too but it didn't last long before the issues started. The end result was a cooked amplifier and a radio with bad ssb audio.

Too much POWA for that amp and it's only a matter of time.

Yup, that other forum member learned a few expensive lessons before they got their station squared away. The good news is the affected radio was sent in for professional repairs and again works as good as or maybe even better than new. And the KL503 is still sitting on the shelf unused since that failed experiment.

 

[9C1Driver]

Let me see if I can remember exactly what happened today. I know I will catch some flack but I’m driving it with a Q5N2. The weird thing that is happening is when I have the amp switched to SSB no TX indicator light comes on. And I can’t hear any relays. But, great audio reports with some long QSOs on side band today. On level 3, which is as high as I will go, because my MFJ meter is only 300W max, I get a clean 250 W PEP. Radio set at 10W PEP. Didn’t have enough to even key the amp with radio power turned all the way down. Nothing even came close to getting hot or even really warm. Even after a long winded contact on FM which I was only on level 2 with a 175W carrier. Just wondering if I should have any concerns with no tx light above the ssb switch and not hearing the relays at all? All seems to be working great except for that.

It seems like your amp is working fine. In SSB mode your wattage is all modulation driven. If you key the mic but don't talk there is zero output so there is nothing to key the amp. The amp will key up when you speak, and if you pause between words the SSB delay in the amp will hold the relay open. In AM and FM modes the carrier is what keys the amp and holds it open.

Be careful talking FM with 175 watts on that amp. Things will heat up very fast if your a long talker and the amp will not last. I would reduce the FM input from the radio so the amp does maybe 80-100 watts. You might want to add a fan to the heat sink of the amp.

 

[Buffalo]

I run it a little higher than that on FM at times and I’ve been known to get long winded. Almost never on AM at all anymore. During the winter months I spent the vast majority of my radio time on FM and conditions were great. More now on SSB. Put a fan on it straight away. Have never even noticed the the thing past barely warm to the touch. Had close to what could have been an hour QSO with a portable station in El Paso from here in south east Texas on 27,390 LSB tonight . Like direct connect once we QSYd first to 395 from 385. Was running between 125 and 150 on setting 1 on the RM. driving it with 9 or 10 PEP from the radio. All well within the manufacturers recommended range. Time will tell I suppose but so far so good and I think I’m being easy enough on it. We will see come fall when I would hope and expect FM DX to pick back up if anything changes heat wise. Long conversation with Tennessee a few nights ago on 315 FM so it hasn’t completely dropped out here. A group up there joined the party and the local buddy I was talking to at the time in his mobile couldn’t believe it was happening. He was on his Lincoln 2 W/102” whip doing 23 watts and told the first guy im having a hard time believing that when he said his qth was Tennessee. LOL A lot of folks still think FM isn’t good for DX.. just ain’t so from my limited experience. I much prefer FM. Anyway appreciate everyone’s input. Living dangerously I suppose.