RM Italy KL 503 Crunchy

[Greg T]

Update:
I want to extend my gratitude to Tokin, a world class gentleman who is an asset to this hobby. With his assistance, my old pal who is post-stroke is now again able to chat with his brother on the air. Unfortunately, my friend is tech illitterate so he cant post this himself. Thank you on his behalf.

 

[Handy Andy]

Wish him the best and for you to be a friend to him in these times...

John 15:13
"Greater love hath no man than this, that a man lay down his life for his friends."​

When you review the "lay down his life" is to take this as you spent a lot of your time to help - and this is also for those others that helped you, to obtain that which your friend had lost in the ability to operate because of his own loss - you've restored his ability to use.

Because of what you asked - others were able to help you regain that which a friend of yours had lost

 

[Greg T]

Not a great vid, but just something to let folks hear what the crunchy KL503 sounds like

 

[Handy Andy]

That is a "pincihng" "FM" effect or you lost a pill somewhere in the amp.

Needs to use the ALC with the amp on - didn't know how low you could go until the "drop out" but that does sound like other issues in there like a popped pill in the amp.

6 watts should be more than enough but not to the point of pinching - so this tells me the amp has a blown part in it and it's fighting itself.

The "stock" radio itself sounds good, no noticeable problems - but you lose dynamics with the amp on, and if power is that low where they have to run words together to keep the amp keyed up - the dynamic range of the stock version - is lost here - the amp needs more work.

Thank you.

 

[Greg T]

That is a "pincihng" "FM" effect or you lost a pill somewhere in the amp.

Needs to use the ALC with the amp on - didn't know how low you could go until the "drop out" but that does sound like other issues in there like a popped pill in the amp.

6 watts should be more than enough but not to the point of pinching - so this tells me the amp has a blown part in it and it's fighting itself.

The "stock" radio itself sounds good, no noticeable problems - but you lose dynamics with the amp on, and if power is that low where they have to run words together to keep the amp keyed up - the dynamic range of the stock version - is lost here - the amp needs more work.

Thank you.

Yup, just what I was suspecting. I think the driver or one of the output mosfets may be bad, but I'm no tech. This amp has a total of 5 minutes of talk time on it. Strange thing, when the amp first arrived, I tested it on my Yaesu with him listening at home. He said I sounded nice and clear. I was driving it with 10 watts. I brought it to his place and hooked it to his Ranger 2980, set it up for 10 watt drive, marked reference points on the mic gain knob for him, and all was working well. That same night we tested it with me at home, he sounded "decent", but for only a few minutes when it began to sound like his audio was failing to reproduce high frequencies. "s" would drop out, "th" would drop out, etc. Now he can barely be understood. He tied his last dime into this and cannot get it repaired, and that is where Tokin came to the rescue, which was extremely appreciated. But since this thing is not usable, I was going to play with it a little and see if I could figure it out. As I said, I'm not a tech, but I have soldering skills and can replace parts. I was just wondering if anyone is aware of this type of thing by the sound of it.

 

[Handy Andy]

My hands are tied at the moment...but at least he has the stock radio - and it still sounds terrific.

 

[Greg T]

My hands are tied at the moment...but at least he has the stock radio - and it still sounds terrific.

Yeah, he's got a nice sounding two-piller doing 200 and that should be enough for him.

 

[Greg T]

UPDATE:
Charlie dropped by and wanted me to test his 503 on my radio. Connected to my Yaesu FT-990, driving 12W PEP the Crunchy 503 puts out 450W PEP and is as clean as anything else. Crystal clear audio, no dropouts and the SSB delay works perfectly. I even purposely overdrove it a bit with 20W PEP and it was as clear as a bell. For some reason it does not like his Ranger 2980. Go figure.

 

[Chris Lawrence]

You’ve probably gotten all the info necessary for this question but here is a bad pic for you to see. I bypassed the driver and it opened up the power a great deal. The kl503 is a terrible idea. The single driver gets overdriven by the radio and can’t drive 8 finals well. I think they have the Hd version now: don’t quote me.

[lQUOTE="Greg T, post: 774501, member: 42791"]Anyone have this issue with the KL503? My buddy just received his and I went to set it up for him. Instructions say 1 to 12 watts pep drive so I set up for 10 watts MAX peak and set the power knob on the amp on #4 so he didn't over power it for it's first run. Amp is peaking around 300+ pep. I went home to talk to him and the audio sux maggots. Esses are chopped, audio is crunchy, doesn't sound good at all. Wondering if we got a bad one or if it may be something else. He's running a 2980 with a D104. Without the amp the radio is clean clean clean.[/QUOTE]

 

[Greg T]

Thanks for the info, Chris. This will prove to be valuable in the future as I may end up with his amp. He's using a small 2 pill from Tokin that seems to sound well. Looks like the mosfets are much more sensitive to noise than an output transistor.

 

[Kristopher burt]

View attachment 49069 View attachment 49069 You’ve probably gotten all the info necessary for this question but here is a bad pic for you to see. I bypassed the driver and it opened up the power a great deal. The kl503 is a terrible idea. The single driver gets overdriven by the radio and can’t drive 8 finals well. I think they have the Hd version now: don’t quote me.

[lQUOTE="Greg T, post: 774501, member: 42791"]Anyone have this issue with the KL503? My buddy just received his and I went to set it up for him. Instructions say 1 to 12 watts pep drive so I set up for 10 watts MAX peak and set the power knob on the amp on #4 so he didn't over power it for it's first run. Amp is peaking around 300+ pep. I went home to talk to him and the audio sux maggots. Esses are chopped, audio is crunchy, doesn't sound good at all. Wondering if we got a bad one or if it may be something else. He's running a 2980 with a D104. Without the amp the radio is clean clean clean.

[/QUOTE]
I just bought the 503 a few weeks ago to replace a 203 that works as it should. What a disappointment. It was like the tease of more watts but could only use the same as the 203. Both the 203 and the 503 for me will start to back swing at around 40 watts dead key from the amplifier. Now I expect the 203 to be weaker but keying down 40 watts and swing to 60 watts or so was ok with me. I expected the 503 to give me at least more than that cleanly. As I plan on not stressing these units out too bad with crazy power. That 503 gets way to hot, much faster than the 203. Only with a 1 1/2 watts swinging to at most 2 1/2 watts into the amp. And power out over 40 watts back swings and sounds sloppy and poor. I'm going to try this modification as I have nothing to loose because I feel I have lost already. This will be the ditch effort. I normally have to mod my equipment to work at its best capacity. Your diagram is the only resource I have found to help me. Thank you for posting this. I will update on this amp because if this works like the report says, it's a great deal at only 209$ new at the 88 place. Yes it's a shady site and was taking a gamble if I would actually get this unit. Thanks again fellas!

 

[Recon]

He can't use it on AM because the radio is much too hot. The RF power control only goes from 16W down to 10W carrier. The low power pot inside has no effect. So this will be a SSB unit only.
Although I didn't hear it at the time, I tested the amp on my Yaesu FT-990 @ 10W pep before we set it up at his place, and he said it sounded great to him. Now that it's at his place .... not so much. I will tell him to start at zero with a long count and slowly turn it up while I listen. And crank the amp wide open.

PS. Just had a thought. His radio does about 25W pep on SSB. Would it be a simple task for a decent tech to bypass the driver and let his radio do a little more work?

I have a 2980. The HIGH dead-key is set at 5 watts and the LOW dead-key is at about 1 watt. I'm feeding a two-pill with the 2980 and it works great.

 

[Kristopher burt]

I had failed to mention earlier that I am running 4 rack units for superb voice communication that I want as clean as I can get. I understand I probably am the only fool trying to make a 503 sound well. This is just what I have and I try to make the best of it. I'll post the results of the experiment for all to know. If it works with clean audio and 150 clean smooth problem free watts, I'll buy another and repeat. I don't think that is asking a lot out of the unit.

 

[Kristopher burt]

Thank you To all on this thread! I have done what Mr. Lawrence has shown to do with his pictures. I have the 1.5 version of the 503 board for reference. I am learning as I go and very appreciative of others input. I have completed this modification to a non HD KL-503. Disengaging the driver for this amplifier has made all the difference. Before the disengagement of the driver this unit was very squirrely and unstable as far as output and had drastic changes to the SWR and wattage output from the attenuator knob depending on the dial setting. The heat was obnoxious for the little amount of wattage I was testing the unit at. This amp would get HOT. My 203 at the same output would just be warm to very warm if i was long winded. Reminding that I would only do about 50-60 watts at the pep output of the 203. With the modification for the 503 that puts the driver out of play has tamed this unit tremendously. I didn't want a high drive version because I wanted this unit for low wattage units, but before this modification I took this unit out of service and play. This modification has brought this unit to full service and replacing the 203. Dummy load tested and I have clean clear audio and voice even at max setting dumping 30 plus watts into the input of the amplifier. I have switched to a regulated 40 amp power supply and that has also taken most of the hum out of my signal with this unit on max over the air. Sideband works well also. no complaints. I still notice that after about 40 watts on the output of this amplifier on the average wattage setting this unit will start to back swing just like my 203. This unit will still sound sloppy if it backswings majorly. This amplifier may be better suited for a radio that doesn't have all of the audio doodads like I am running. My Kenwood that i am experimenting with is very wide in audio bandwidth so i am able to hear all the voice imperfections that are in need of cleaning up. Thank you to all who have chimed in on this thread!

 

[Shadetree Mechanic]

Bump