Another XTL500 Problem

[kt2728]

I have an xtl5000 that I felt the receive wasn’t working as good I thought it should. Then I noticed that I wasn’t able to key some repeaters that I knew I should be able to key up. I have a mid power Kenwood analog radio in the same vehicle and this radio was able to key and receive repeaters that my high power xtl couldn’t. My next thought is this has to be an antenna problem, right. Well that evening I check the antenna with an analyzer and the antenna tests good.

So I check the transmit power from my xtl and nothing not even a wiggle on the 5 watt setting on my bird meter. So I dissemble the xtl and pull the board out and look at it. I am not sure why I did this, I don’t have the equipment to do soldering on surface mount stuff. I put the board back in the radio and set it aside. After speaking to Jim about this problem and he asked me if the radio was still pulling full current for a high power radio, I hadn’t checked that at this point.

So after I got off the phone with him I hooked it back up on the bench and I noticed it was pulling about 20 amps. Then I glanced at the bird meter and had full rf power out. ????? WOW I can fix radios by just pulling the boards out an putting them back in. Well that’s not the case neither. So I left the radio hooked up on the bench and used it for a day or two. Now its back to barley any rf out and it is still pulling the full current.

Jim had said something could be going on in the antenna circuit. Has anybody seen this kind of problem out of one of these high power radios? Is this something that can be fixed by someone in the field or is this a depot trip?

Any advise?

This is 2 xtl500s I have down at this time. This is starting to get real expensive. lol

[wa6ylb]

I would look at the female mini UHF connector on the back of the radio itself. These connectors are very susceptible to being "raped" thus leaving the antenna cable not making connection. What I mean by this is, that if a soldered center pin , on an antenna plug, has a blob of solder, that causes the OD of the center pin to be much larger than the normal OD of the pin, this tends to spread apart the female connector, on a permanent basis. Also look at the antenna plug itself. Some folks crimp them, some solder the center connection. If the crimp is right at the end of the plug that goes into the antenna jack first, it is possible that it’s not making connections.
Our shop uses 100's of mini UHF connectors per month, and all ours are soldered, but the guys know not to leave a blob of solder.

[tvsjr]

Wow... raped connectors?

[wa6ylb]

Wow... raped connectors?

Yeah, I wondered what had happened to this connector, so I took it apart. The female contacts are made up of two arms, with semi circle contacts. Once they are spread apart farther than normal, they didn't return to a closed position.
Next time a come across one of these that has failed, I'll take a picture of it.
B.

[tvsjr]

Oh, I know what you're talking about... seen it before - also when someone mismatches 50- and 75-ohm Ns. I was chuckling about the description...

[kt2728]

Well i have good news, my mini UHF female has not been raped!

i have pulled the board back out or the radio and the solder connections at the antenna connector dont look so good. i am going to re-solder them.

ill post my results later.

[kt2728]

It looked like a bit of flux or corrosion around the solder pads on the board. i also got to thinking about something Jim told me in one of my conversations with him. Motorola uses only leadless solder these days. i also didnt think about it at the time i did the the installation but i used a pair of pliers to snug the mini-u connector up to the radio. After i disassembled the radio i realized that the antenna connector is not bolted to the chassis like the astro spectras i got to thinking about the solder and the pliers. so i heated up the three solder points and re soldered them re assembled the radio.

The radio has had full power out since saturday and the receiver is working like it supposed to. i have left it on the bench and hooked up to the bird meter and i have checked it every time i have keyed the radio up. So far so good. All i can figure is when i snugged up the antenna connector i tweeked one of the solder points to where it didnt make a good connection.

Lesson Learned: Do NOT use pliers to tighten up the antenna connector on an XTL radio.

I guess i got lucky on this radio and didn't have to send it to the Depot. i will keep it on the bench for a week or two just to make sure it holds and doesnt give up again.

[com501]

Quarter turn past shear?

[wa6ylb]

Quarter turn past shear?

Lets see... How many foot pounds is that???

[kt2728]

too many!


this radio radio has been on the bench for two weeks and has not failed yet. i have transmitted on it every day and so far so good.