Archive for category Things that are Busted

On the use of Power Amplifiers in Amateur Radio

As many of you know, I’m a ham operator. I spend a lot of time listening to the HF bands, not a whole lot transmitting, but I do listen. One of the things that tends to irritate me is when I hear some wag putting someone else down because they have a “little signal”, by which they mean 100 watts or so.
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New WordPress version, new MySql version, hoop jumping, aggravation

So, my legions of loyal visitors (notice how I don’t assume you read any of my drivel, just that you visit), my hosting provider informed me that things were changing, and I’d have to update what database I was using and what version of the underlying language, and that also meant new blogging software, and so… the site was down for half a day or so while I located the hoops, jumped back and forth through them, and towards the end, contemplated setting them on fire.

But it’s done now. I think. Perhaps.

However, should you encounter weirdness, by all means let me know and I’ll see if I can work out what I did wrong, or whatever. Sorry for being down, wasn’t my intention.

Cheers!

–Ben

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Marantz MA700 troubleshooting

I have quite a few Marantz MA700′s; of the group, four of them exhibit random popping sounds of moderate energy at the speaker output with no audio input to the unit. Clearly this is a very common failure mode for the MA700.

I have opened one of the “poppers” up on the bench, and with the buffer amplifier signal cable to the power amplifier disconnected, the popping noise remains, so it’s definitely not in the audio path on the buffer amplifier board. The buffer amp is connected to the power amp via an electrolytic, so there’s no problem unplugging the buffer from the power amp.

There’s another problem with this unit, too: I see somewhat random engagement of the high power rail mode for the amp, but this is not co-incident with the clicking coming from the speaker.

When the high/low power state switches randomly, the associated relay clicks, which is audible at very low volumes, and this is obviously not the design intent. Erratic high/low power switching problems are going to be nearby QU05, very likely the electrolytic CU08, the diodes DU01 and DU02, or QU05 itself. I’d suspect CU08 first.

The main amp PCB shows evidence of excessive heating towards the front of the chassis, where the driver section is located. Unfortunately, it looks to me that the mechanical assembly is complex with regards to the main amp and attached heat sink; taking it apart looks to be quite a big deal, my vision has become very poor, and I don’t actually need the amp, so I’m just going to close up. However, at least this exonerates the buffer amp and provides a pointer as to how to troubleshoot high/low rail power issues.

If anyone locates a specific component that is responsible for the clicking and popping, I would very much appreciate hearing about it; I’m willing to hack in a replacement electrolytic from the component or solder side of the board if that’ll solve the problem. Likewise, if circumstances lead me there — if one of my working MA700′s fails and I really need to fix one of these “poppers” — I’ll post what I’ve learned.

I’ve put the service manual for the MA700 online here.

–Ben, AA7AS

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WLO RTTY News Feed Replaced with Weather

Sad news for RTTY SWLs, WLO’s newsfeed at 8473 kHz is gone, replaced with weather broadcasts. The weather broadcasts alternate between RTTY and SITORB, just as the news feed did, but that’s the end of the similarity.

Well, it was nice while it lasted. Sigh.

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Cellphone Etiquette at the Table

Wandering though life, I often encounter the occasional person who seems to have missed an etiquette class. Or several. In particular, I have noticed that a very large number of gaffes occur at the dinner table. So as a gift, I provide the following guide to using your cellphone when sharing dinner with family, friends, and friendly companions:

Rule #1: Don’t.

Rule #2: See Rule #1

If your phone rings, vibrates or plays an obnoxious ringtone (all ringtones are obnoxious) there is only one polite action: Turn it off or mute it, while apologizing: “I’m sorry, I forgot to turn my phone off. Fixed!” Slip it back in your pocket and deal with it later.

In an upcoming post, I will cover cellphone use during conversation with another person. I’m sure you all look forward to that.

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The 2012 Election – I Surprise Myself

8142797777_17cc1e55ec_nDeb and I had the pleasure of meeting some of the key democratic candidates for office for, and within our state (Montana) today. Each spoke for a few minutes about their aspirations, and spent some time “working the room”; I bent a couple of ears, as anyone who knows me might expect, and got some fairly good answers, actually.

I don’t normally jump on a soapbox, politically, but this year… here we go.
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The Constitution is not just a piece of paper

rippedObama has (and let’s be fair here — also the congress, and the judiciary, and state officials have) repeatedly demonstrated either a complete disrespect for, or absolute misunderstanding of, the constitution.

From the inversion of the commerce clause, ex post facto laws at both the federal and state levels, sweeping usurpation of article 5 powers via the judiciary, to blatant violations of the 1st, 2nd, 4th, 5th, 6th, 8th, 9th, 10th and 14th amendments, our government is — at best — operating in an unauthorized fashion, wielding powers it was never granted by the people, and ignoring its obligation to protect the rights it was explicitly charged with protecting in return for being allowed to operate at all.
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Predicting where IOS and OS X will go

Every time I read one of the sycophantic articles predicting OS X is going to become like IOS, I have to laugh. That’s not going to happen, at least, not in the long term. So in the spirit of the new year, when every fool (I’m speaking most definitely of myself here) proceeds to stuff foot deep into mouth, I offer the following IOS, OS X, iPad and iPod predictions:
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