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Re: LM-386 Live or Die?

 

Okay, the progress so far.

Kit: WWVR Receiver, marked Ver. 3 - 11/21

Probing around for a couple of hours I verified that +12-volts is getting to where it needs to be. I only have the 2019 schematic available from the website, but I was able to verify that good power got all of the ways to the 78L06 6-volt voltage regulator. The ground pin on that device also was good and verified all of the way back to the input connector. Things were checking out great until I got to the SA612 mixer and the LM386-4 audio amplifier. The schematic shows multiple points grounded on the ICs and they turned out to be connected together as shown at the ICs, caps, varactor, and trim pots, but not then back to the 78L06 voltage regulator. There is a break in the ground plane that also does not include a lot of the .1uF filter caps which IS connected to the IC ground points. As far as I can tell with my tired, crusty eyes, that is the only break in the "circuits". Not having the 2021 documentation there might be a mod jumper that I am not aware of, but I am not aware that there was such a document posted, this is just speculation. After I get some coffee and let my eyes settle, I am going to place a jumper from the VD1a ground pad to the +12-Volt Ground pad about an inch and a quarter from each other. I will post my results later.

I purchased a stack of 10 LM386-4s and?SA612ANs that should be here in the next few days. I suspect I may have trashed my LM386-4 during the troubleshooting phase, but at least I did not let out the magic smoke. We used to get special trophies from the department manager in Test Equipment in aerospace when we let out lots of smoke, some thought it a badge of honor, I usually went into tomato mode during that meeting of 150 engineers with very, very big egos. I was so much not into the big ego thing that during that phase in my life, I had my 2-foot-long beard, LOL.

Cheers,

Davey - KU9L

On Sunday, May 7, 2023 at 09:27:36 PM MDT, David Knapp via groups.io <renewables@...> wrote:


My version of the Sudden Storm Kit is Ver 2 and I can only find the original or Version 3 on QRPme.com, so there will no doubt be some minor differences. I do not have access to the computer I used in 2016 or I might have exact documentation stored there. I will compare the parts list with the Ver 3 build guide and schematic to see where I stand. Tonight I had 4 hours of onboarding online training with my work and for the next two days, I have all-day meetings with the USFS in Woodland Park 2+ hours away, so I will get back to assembly ASAP. Cheers, Davey - KU9L

On Sunday, May 7, 2023 at 10:49:10 AM MDT, David Knapp via groups.io <renewables@...> wrote:




This was just before I assembled the 10.0Mhz 30M band module. I am using a 20-watt Elecratt DL, 12.3 volt supply from two Lifepo4 Lithium batteries reduce to 12.3-volts. Alternative antenna is a half-wave wire into a Tuna Tunah half-wave tuner I am testing on my Penntek TR-35. My headphones do work, I have plenty of QRN from the led lights in the RV, but I also use them on my Penntek when doing POTA hunting.

Davey - KU9L


On Sun, May 7, 2023 at 10:34 AM, David Knapp via groups.io
<renewables@...> wrote:
I have a WWVR Ver 3 receiver that I have been troubleshooting using my standard aerospace electronics methods to eliminate any assembly errors. So far I haven't found any since I took the whole evening and basically triple-checked as I went and also rechecked with my dental tools to locate any hidden shorts or opens. Fortunately, these kits are very easy to assemble with fewer parts than my old Heathkit days. However, upon powering up, I do not yet get to hear the familiar sound of hiss in my headphones.

I do hear a loud click in the headphones, followed by a soft low-frequency buzz from my 12.3-volt buck converter supply. After a few seconds, it switches to silence for 1/4 second, then repeats endlessly with the low-frequency buzz & then silence cycles. I can only find the Ver 1 documentation and I have a Ver 3 board so there may be an assemble detail I may be missing.

I have a Sudden Storm Ver 2 kit unbuilt, so I borrowed the LM-386-3 and the SA612 from it. This time there is just a soft click in the headphones and no hum or his, total silence. Antenna or dummy load, nada, nothing to Hiss about. There is not change with the SA-612's swapped. No change with the Varactor installed or not. There is no change with the band module installed or not.

I may build the Studden Storm I have just to make a comparison. First I have to check on a few campgrounds I haven't opened yet to see how deep the snowdrifts are and to see if I can get in there to drop off the Host's water tank and get to their golf carts to install the batteries. But I look forward to a little sudden storm action later tonight. I might have been wise to order up a few LM386s ahead of time. Fortunately, I have been following my aerospace ESD practices, however, at 23% relative humidity it is only going to get drier in here as the summer progresses. It is still getting down to freezing every night and we expect a few more snows before the holiday weekend when I really start to get busy for the season.

Cheers,

Dave David Davey Knapp, depending on who is asking - KU9L
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