An excellent, well-reasoned discussion. 73
Ken Kopp - K0PP On Mar 9, 2014 10:23 PM, <[email protected]> wrote: > Hey Rich, > > > Problems like these can be very frustrating. Not lecturing to you, but > take a deep breath. You will get it going. I know the tendency is to > throw the baby out with the dirty diaper (or however that saying goes) but > from my experience and what I am reading we have a very good amp in the > KXPA100. I started my career in electronics 42 years ago and 9 times out > of 10 the reason for a problem is really quite obvious - once it is fixed > that is. :) > > > > > I don't see where the schematic and firmware is available for the KXPA100. > It may be, I just don't see it. But lets do some logical troubleshooting. > First, the front plate and the nut have nothing to do with the operational > problem. Granted, it shouldn't have happened but it did. Elecraft made > good on it so that one is no reason to be talking about returning the amp. > The two are simply not connected. I will say that I had parts problems > with mine also - not Elecraft's but my bone-headed failure to read the > Eratta. I twisted off a standoff lug. Elecraft sent me a new one. And > guess what, I wasn't really short lock washers either, I just didn't read > the part that said I didn't need them under the standoffs. Duh! So it > sounds like your parts situation is OK now. > > > So, the KX3 seems to work fine going around the amp. That tells me your > problem is definitely in the amp. OK you knew that. But there is no need > to be changing out the tuner and what not. The problem is in the KXPA100. > I buy that. It appears the KX3 is talking to the KXPA100 just fine. It > recognized it and adjusted itself for proper power etc. That is an RS232 > serial interface so there isn't much that can go wrong with it. All of the > data goes down 1 wire. Unless it intermittently and randomly just starts > switching or tuning or changing something, I wouldn't suspect the RS232 > link. It should either work (as it appears to be doing) or it doesn't. So > there is no need to mess with that interface. > > > The SWR of 99.9 is probably not so puzzling when you think about it. What > would happen if you didn't have any antenna connected? Or if the antenna > connector or cabling were shorted? In theory, the SWR would be infinite. > But I suspect the firmware in the amp can't handle infinite SWR too well. > So I am guessing that when SWR goes over a particular limit it just says, > "The SWR is too freekin high. I am just going to display 99.9 to tell the > user it is way out of wack." I suspect that what is happening is that your > antenna is not really connected to the radio when you think it should be. > If your amp is seeing an open antenna line when it tries to transmit, you > should see what you are getting. Now stick with me. The fact that you are > seeing some weird switching indications between ANT1, ANT2, and Bypass, > tells me that you may have your coax connectors inside the amp connected to > the wrong receptacles on the board. I don't know how that would effect the > LED lights and su > ch, but it could sure mess up operations. Ask me how I know? When I > first powered mine up, I noticed the KX3 was very very quiet. More so than > it should be. So I started playing around and discovered that when I > connected my antenna to the ANT2 connector I got an increase in noise. > HMMM! Switch to Antenna 2 on the KX3 and the noise drops to nothing. > Move the antenna cable over to the ANT1 connector and it comes back. I > had crossed the ANT1 and ANT2 connectors when I plugged them into the board. > > > Now in your situation, you may have something similar. I don't know what > the switching circuits and relays all look like in there, but it appears > that your problem could be similar. There is one symptom you mentioned > that I can't answer. You said you were getting 30 or 40 watts out of the > big amp instead of 300-400. I don't understand that. If the RF drive is > not going into the amp, I would say you should get zero output. Maybe > there is something going on there with keying the amp with no drive that > would cause some strange meter readings. Or maybe the coax cable in your > KXPA100 is partially open or shorted. > > > Anyway, I would open up the KXPA100 and double check those connectors to > be sure they are plugged into the appropriate sockets. You could also get > an infinite SWR if a cable were almost fully shorted. Check for that also. > Also check to make sure you didn't flex the cables so much that one broke > off the back of the SO239 connector. Finally, double check to make sure > that when you plugged in the tuner board you didn't bend or miss a pin in > one of the connectors. Just triple check, I know you have double checked. > Then hook up your antenna again to the KXPA100 (the big amp isn't needed > for this troubleshooting) and use the listen test I mentioned earlier. You > should be able to tell pretty quickly if you have a good path between the > antenna and the radio through the KXPA100. You should then be able to > switch antennas and tell that everything is hooked up cleanly and you have > good paths and everything is switching properly. Having a dummy load to > test with is a good idea > but you shouldn't need it until after the listening test. Finally, if > all is OK and you still can't find anything, it may be time to send it back > for a look see. Contact Elecraft and they may have more ideas, but I bet > they will works something out with you if it can't be resolved over the > phone. > > > Good luck and let us know what you find. My money is on something simple > only because I have made so many mistakes in my career that I have learned > to trust the equipment and look at myself first. If I had a nickle for > every time something worked worse after I worked on it than before, I would > be rich! Hi! Keep your chin up and keep on keepin on. Let us know how it > goes, please. > > > 73, > > > Tom/AE5QB > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[email protected] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
