Tuesday, April 15, 2008

Good News, Bad News

Last week, I worked VK6DXI, located in western Australia, on 40m CW. This was a nice contact for a couple of reasons. First, it meant that I'd worked a new country on 40m for DXCC purposes. That's always nice. But more important to me is that I'd finally worked a "real" zone 29 station.

By way of explanation, CQ Magazine offers an award to amateur stations that have contacted other stations in each of 40 global zones. As you can see from the map, some zones will be more difficult to contact than others, depending on where you are located. I'm located in CQ Zone 5, which covers the eastern seaboard of North America and the Caribbean. Some zones are pretty easy to contact (like Zones 14 and 15, covering much of Europe), but others are a lot harder. From my location, I'd have to say that Zone 29 was just about the hardest, although there's one catch that makes it a bit easier: All the most southern zones actually converge at the South Pole. Because of this, any station worked located at the actual South Pole (not just on Antartica), counts for any of the zones that converge there, including Zone 29.

By using that rule, I'd actually worked all 40 zones a while ago which would qualify me for the Worked All Zones (WAZ) award previously mentioned. I'd never gotten around to submitting the required cards for the award, kind of thinking that I'd like to finally work that 40th zone "for real". In fact, just a couple of days before working VK6DXI, I'd commented to a friend at a club meeting about how that zone was still something that I was trying to contact. So when I heard the station on the air, with surprisingly good conditions, I called him and finally was able to make a contact with him. I sent for his QSL card the next day.

Here's the bad news: Instead of using my Icom 756 Pro II to make the contact, I had to use my Icom 706 MkIIG, sending CW without computer assistance (I freely admit that my CW "fist" is terrible) and struggling a bit to hear the VK6 station without the benefit of the terrific DSP filtering on the 756. Why, you may ask? Gee, thanks for asking ...

A day or so before that contact, I'd come home after work and was tuning around trying to find some interesting DX to work. There was YO22NATO on 40m CW, so I figured I'd give him a call. As soon as the first dit was sent, the fan on the 756 came on at high speed, and stayed on. I'd rarely heard the fan at high speed (if I heard it at all, it was after operating RTTY for a relatively extended period), but certainly never after having the radio sitting in receive all day. (The radio had been on since the morning; I'll sometimes turn it on before work and I just don't bother to turn it off.)

I felt around toward the rear of the radio to see if it felt hot, and indeed it did. Normally, after sitting in receive, the radio might be a little warm, but not hot. However, this time it was hot. I actually did make the contact with the YO22 station to see if the meters on the radio indicated if it was putting out full power. The meters did indicate that, but later, after looking at the schematic [PDF] and with some help from a 756 theory of operation manual [PDF], I realized that the power meter was basically feeding off the drive circuit, not the power amplifier. That meant that without an external power meter, I couldn't really tell if the radio was putting out 100w or whatever the drive power is, which would be quite a bit less.

Then things got really weird. I turned off the radio, but not the power supply, and realized that the radio, while turned off, was drawing around 4.5 amps from the power supply. That is most definitely not normal. I tried disconnecting the fan on the theory that maybe somehow the problem was there, but that didn't have any effect.

I posted a question to the 756 Pro users reflector, and most comments seemed to indicate that it was likely to be something wrong with the power transistors. The suggestion was to send the radio to Icom for repair. I sent a note to Icom explaining the symptoms, and the technician who responded said he thought that most likely it was a shorted final power transistor, which would explain the heat and the power draw when powered off, and recommended that I send the radio in for repair.

So I've got the radio all packed up, double-boxed as instructed, and it'll go off to Icom tomorrow. Here's hoping that the repairs don't cost as much as the radio.

One final unrelated note: Next month is the annual Dayton Hamvention®. I still haven't had a chance to go, but I've read plenty about it, given that it's arguable the largest hamfest in the world. If you find you have a chance to go, Scot, K9JY has posted a "Preparing for Dayton" entry to his blog that has a bunch of great tips. If you haven't seen it already, be sure to check it out, even if you aren't going.

2 comments:

  1. w4kaz9:49 AM

    I hope your radio repairs are inexpensive. Seems unlikely.

    If you ever get a chance to go to Hamvention, don't miss it. If you like ham-fests, the Hamvention is not to be missed.

    73 de w4kaz

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  2. Yeah, I'm thinking that I'm not going to get away cheap. It looks like the PA transistors are around $30 each (I assume they'll be replaced as a pair) and labor is $84/hour, then there's the return shipping.

    Well, according to FedEx, my radio is out on the truck for delivery today, so hopefully I'll hear something from Icom today or tomorrow to give me an idea of what to expect. I pre-authorized a pretty hefty amount for them to fix since I figured that unless the radio is totally trashed (which is clearly not the case), I'm going to pay to have it fixed. I'll post an update when I have something more concrete.

    As for Dayton, I'd really love to go, but for years, it seems that things have conspired against being able to go. The really tough part is that I've been unable to commit in advance to going, meaning that getting a hotel room would likely be a challenge even if I could go. Well, someday ...

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