开云体育

As I've seen a few people post about magic smoke and RX issues I would point out that when I received my sBitx (the version with everything except the pi4) on Tuesday there were several extra loose nuts under the main board and one that had lodged up pretty tight.

On a side note last night on FT8 20m I transmitted a quick CQ and PSKReporter showed reception from Southern California clear up to British Columbia Canada. My QTH is about 20 minutes west of Kansas City. My antenna is a homebrew LMR400 magloop.

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Support@...

Check for loose screws and nuts - solved

I checked too, even though I didn't have a loose screw.
To do this, you must first remove 4 screws as described on page 35 of the attached 40-page manual.
The device housing is very solid, the individual parts fit tightly. You can use a plastic knife to remove the parts.
When I unpacked it, I started to check the condition of the screws, how stable they were.
I found that almost all of them were screwed on tight. However, mounting the power-stage FETs to the heatsink is not the best.
A threaded spacer stub is pressed into the heatsink 2mm long, which turns out to be not enough.
When I wanted to check the strength of the screw-in, I lifted it out of its place.
It turned out that the screws were M3x5 mm and the spacer released the heatsink.
My solution: I didn't want to take it apart any further to make the heatsink stand alone, so I used Kapton tape to tape off the surroundings so that the chips from drilling could be removed. I completely covered the surface of the two FETs so that the chips brought out by the auger drill (d= 2.5mm) would not cause problems later.
I used a vacuum cleaner to remove the shavings. I fixed the falling spacer with liquid glue containing cyanoacrylate.
Do not take the whole tube to the place to be glued, but squeeze out a drop separately and use the end of a screwdriver to take it to the required place.
I then cut a thread into the pre-drilled hole with an M3 tap.
I replaced the previous screws with M3x10 mm so that the screw can also be held in the heatsink.
That's it, now the fixing of the screw proved to be stable.

By the way, the insertion of the RPi also fits tightly in the given place, handle the insertion carefully.
Before assembling the device housing, check whether the connectors are in place.
I made a copy of the uSD card included in the package on the win7-32 pc using Win32DiskManager before inserting it into Sbitx.
The power-on operation went well. The parameters can be set next.

Overall, I like the build of the device and its current knowledge. I trust in further developments.
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Gyula HA3HZ

Thanks for that timely reminder, Gyula. I knew I had read it before but could not get the search engine to find it.

So, in effect you deepened the tapped hole in the pressed-in spacer, once it was refixed in place with cyanoacrylate glue, such that the screw now also engages your extended thread on the heatsink base? If I have understood your description accurately it would essentially be the same as my suggestion to Ashhar that HF Signals taps the base of the heatsink and uses a separate spacer.

Cyanoacrylate glue is commonly known as superglue here in VK but in its most frequently found fairly liquid form does require a close fit for reliable adhesion. I guess some of the gell types might be less demanding in that regard. It was that concern that led me to think about using epoxy resin, with its inherent gap-filling properties. The other alternative idea?,thread lock or Loctite type product, I didn't favour as they tend to need a relatively airtight fit before they will cure.

I like your added security provided by the washer and spring washer allowed by the 10mm screw length.

Your tapped spacers hadn't actually lifted out of the heatsink when your V2 arrived? One of mine had, and Joe reports a similar case. Collectively though, our three experiences indicate that a mod along these lines needs to be adopted by the factory as a priority, I would suggest.

73
Bill VK7MX & VK1MX

Bill, glad to be able to help on this topic.
You can use any kind of glue, its role is limited to drilling and screwing in the longer threaded shank.
In fact, you fix it against falling out again.
Because the M3x10 mm screw screwed into the aluminum heatsink can sufficiently secure the FETs to transfer the amount of heat they produce to the heatsink. The M3x10 mm screw may be sufficient for fixing, because this size screw is not visible from the back.
Since I had such a metric screw, I added this, but you can also use a so-called metal plate screw if you can find one in this size.
Then you don't have to drill a thread into the cooling fin, because it can be screwed directly into the D=2.5mm hole.
You can use any transparent foil adhesive and use a vacuum cleaner to remove the shavings from drilling.
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Gyula HA3HZ