Re: [IC-7000] More Smoke than RF
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Bill,? I don't have any experience with the AT-180, but most autotuners tend to act strange when switched among a variety of antennas. ?There doesn't seem to be much band overlap in your setup, unless you occasionally use the G5RV above 40M, like many do. ?Having memory settings for a frequency on one antenna that may be low Z and -X, then switching to another antenna that is higher Z and +X tends to be rough on the tuners. ?And as you skip around a band, retuning occasionally, it's easy to hit a lot of rough spots. ?You might try to eventually simplify your antenna farm -- your autotuner will probably behave better. I have an LDG AT-7000 and an SGC-237 that are used at home occasionally and mostly portable. ?I always (well almost) reset them when setting up at a new location, otherwise they are sometimes unpredictable. ?I use a 4-band fan/parallel dipole and a tri-bander at home with no tuner. ? But portable operation (on ham and MARS) varies a lot and neither tuner was happy with prior memory settings. ? The problem you described as detuning on digital modes and wide variation of ALC & Power values sounds like a real problem that warrants attention. ?Do you have common-mode chokes at the feed points? ?Asymmetrical antennas like G5RV's present a very unbalanced load, which causes excessive RF to flow on the outside of the coax shield. ?This leads to RFI in the shack, which creates problems on tuner control and power lines and also on audio lines (leading to ALC and TX power fluctuations). Much of the current on the outside of the shield is shunted to ground at the lightning suppressors, but grounding wires have enough inductance to allow significant current inside the shack. ?A properly designed common-mode choke will stop the problem at its source, which will also prevent the feed lines from radiating RFI into the house/shack. ?Ferrite chokes on audio and control lines will help reduce it further. ?Fair-Rite Type 31 clamp on chokes from Mouser.com are best for below 10MHz (and above also, although Type 43 are OK above 10 MHz). ?The best info on common-mode chokes, baluns, grounding, etc. is at: http://www.audiosystemsgroup.com/K9YC/K9YC.htm It sounds like you've done a good job with lightning suppressors and grounding. ?You didn't mention if all of your lightning, radio and electrical grounds are bonded together with #6 copper wire. ?That's a critical part of the grounding system. Regarding the possible Driver failure, I haven't seen many such failures first hand, but there seems to be a common theme of either running at reduced power or flakey autotuning. ?I've spent several days looking for ALC problems at reduced power and at RF levels around the driver during the "search" phase of the tuning cycle, but haven't seen anything that resembled a problem in my two 7K's. ? Many owners blame heat for the Driver board failures, but that doesn't seem likely, in my opinion. ?Although it is truly a mystery why Icom doesn't put thermal compound between the heat spreader and the aluminum casting of the case! ?But thermocouples on the FET don't indicate there is a problem that would result in catastrophic failure due to thermal overstress or runaway. Let us know if you find anything interesting with the tuner or 7K. Steve, W3AHL ---In ic7000@..., <william.lifsey@...> wrote: Steve, For lightning protection, I have Polyphaser blocks (grounded externally) on each line prior to entering the shack.? All lines then connect to an Alpha-Delta switch in the shack, which also it's own gas-arc plug.? The switch is grounded to my shack ground system, which is a 10 ft copper rod I sunk through the foundation of the house. I have two primary antennas: a homebrew 40m dipole, which also works very well on 15m.? Without tuning, SWR is 1.2 or lower.? The other is a G5RV Jr., for every thing else above 40m.? This antenna has always been easy to tune to a nice, low SWR.? I rotate through a selection of other antennas, right now I have up a 10m dipole (1.1 SWR without tuner across the SSB portion of the band) and a homebrew G7FEK 80m (1.3 SWR) with a 160m mod (1.8 SWR).? The AT-180 brings all of these down to 1:1, at least that's what the meter shows me.? I will also run up a 6m or 10m Yagi, and these are normally 1.5 or less - pre-tuning.? I've suspected the autotuner in the past.? I did send it in when the pre-amp FETs blew the first time.? ICOM said it was functioning normally.? It has difficulty holding TUNE on 30m since it came back, not a problem I had before.? When I sent the -7000 in a second time, it was for unusual behavior I noticed during operation - not any obvious failure.? There were some very wide fluxes on the ALC and Power meters during SSB, far beyond what I was use to seeing.? I probably should have sent the AT-180 back in as well.? ICOM replied that the -7000 was functioning normally. When the IC-7000 returned, I had even more severe problems and it seemed like the -180 just wasn't wanting to comply.? I put the -180 through a home version of a factory reset, running several heavy tuning cycles across all HF bands into a dummy load.? Two cycles of this had the AT-180 back to normal function, except for my issue with 30m.? It's not really a problem with CW, but it will "detune" on longer digital mode transmissions.? I don't operate on 30m much, so it wasn't really bothering me.? After I got the AT-180 back in shape, the wide fluxes I had observed went away.? I believed I was probably suffering from a lack of operating experience and paranoia more than any hardware fault(s). The system has been running flawlessly since late June.? I was happy. When the IC-7000 was in the shop the first time, I picked up an IC-718 and put an LDG IT-100 tuner on it.? Granted I have not run this rig setup near as much as the 7000/180, but I have not had any problems with this set up in my station.? I did operate a couple of contests with the -718, so I've put it through the same stress loads and operating conditions as what I had the -7000 plugged into. I'm willing to accept there may still be flaws in the rest of my system, but I think I've done a reasonably good job making sure there aren't any more.? The short in the jumper line taught me a hard lesson.? I'm more willing to believe that the initial short caused additional problems in the -7000 than just the FETs, and it's taken a little more time to expose those weaknesses. I do like your suggestion about the tuner, and I will take it apart tonight.? Even if I don't find anything, I might as well send it back to ICOM for another look since I'm paying for shipping anyways. I really do like my -7000, and I've met many who have been running them for years with rock solid performance.? Investigating where the smoke came from, it looks like the driver unit area - which seems to be a prior problem based on other online postings.? I'm just wondering what everyone's overall experience has been with ICOM customer support once there have been equipment issues. Thanks again for the tips, Bill AB3TM ---In ic7000@..., <w3ahl@...> wrote: |
Steve W3AHL