What's Coming Up Tonight Here On the ALPB

Deleted
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What's Coming Up Tonight Here On the ALPB Apr 9, 2017 1:42:56 GMT

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Post by Deleted on Apr 9, 2017 1:42:56 GMT

AMT5000 Maintenance

Yes, a couple of things need to be done to the AMT5000...

1.) There's an intermittency in the COMPRESSOR control which causes levels to jump around unless the control is fully CCW.

2.) Previously I modified the audio input section and now want to restore it to the original design.

I will be operating the transmitter into the PhilB Approved Dummy Load.

Dummy load?

Yes! The maker of the AMT transmitters issued a circuit comprised of a resistor and capacitor in series that presents a load equivalent to a 3-meter wire to properly load the RF output without transmitting beyond the workbench.

I will be sure the Dummy Load Circuit is linked and shown for the benefit of you.

Boomer
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The Dog is listening..

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What's Coming Up Tonight Here On the ALPB Apr 9, 2017 11:28:21 GMT

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Post by Boomer on Apr 9, 2017 11:28:21 GMT

I wonder if the wiper inside of the pot is dirty? Little pots don't have that trouble so often, but it's possible, and I'd inspect the pot's connection to its solder pads. I've found those can lift on circuit boards, and cause intermittent problems like that.

Dummy Load that's an intelligent load.

That's a good idea, we always see dummy loads for 50 ohm outputs, but not the high impedance that a 3 meter antenna output needs. Having the fixed, stable load makes testing easier, and radiates very little signal, so you can test in private.

Boomer

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What's Coming Up Tonight Here On the ALPB Apr 9, 2017 15:03:35 GMT

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Post by Deleted on Apr 9, 2017 15:03:35 GMT

Progress in the Slow Lane

The AMT5000 card is on the bench and so far what we know is that the compressor control is "scratchy" throughout its range but when fully CCW or fully CW is noise-free.

Doug wonders: "I wonder if the wiper inside of the pot is dirty."

Right now that is a strong possibility... there is no access to the wiper or the inner surface of the part because it's a fully enclosed type, and all solder points appear solid.

One other thought is that DC voltage might be leaking into the path from a faulty capacitor which will be easy to check.

A replacement part will be added to the parts list that I've been composing for the past year.

Today we should see that "Intelligent Load" circuit published here... I've got that hooked up to the transmitter and the TECSUN PL-310 set alongside to monitor the carrier.

mark Life Member Posts: 1,017	What's Coming Up Tonight Here On the ALPB Apr 9, 2017 15:28:01 GMT Quote Select Post Deselect Post Link to Post Member Give Gift Back to Top Post by mark on Apr 9, 2017 15:28:01 GMT Carl, there's till a way to get control cleaner inside the pot. If there's no small space where the top attaches to the base you can do it through the shaft while turning it and it will get inside. Mark

Post by Deleted on Apr 9, 2017 1:42:56 GMT

Post by Boomer on Apr 9, 2017 11:28:21 GMT

Post by Deleted on Apr 9, 2017 15:03:35 GMT

Post by mark on Apr 9, 2017 15:28:01 GMT