Electronics > Repair

Boonton 41-4B power sensor repair advice

<< < (7/9) > >>

edpalmer42:

--- Quote from: xrunner on October 29, 2023, 12:00:04 pm ---A 41-4B sensor and cable for $60. But one of the connector pins has nothing inside. How well do you think it works? The parts are listed as used which means they works correctly but it's not new. I messaged the seller but no reply yet ...

 :popcorn:
 

--- End quote ---

That could be fine.  It likely means that when it was soldered at the factory, the solder didn't run down far enough to plug the end of the pin.  I'm not aware of any requirement that the wire itself has to go right to the end of the pin.  If I was looking for a cable I'd grab it and inspect it on receipt.  Worst case, you're just resoldering the end of the cable.

Ed

xrunner:
Here's the initial checkout of the repaired sensor. It's working about the same as it was before (whenever it decided to work for a bit). The Agilent 8648A has a stated amplitude accuracy if +/- 1 dB, although I know from many different comparisons of power meters over the years it's more accurate than that, more like tenths of a dB.

On the +10 dBm setting I do know the output is always a little less accurate than the lower ranges (but still within specs) so the Boonton is reading correct there also.

PWR   1 MHz   100 MHz   1 GHz

+10   +9.7   +9.7   +9.5
   0      0.0    0.0       0.2
-10   -10.1   -9.9    -10.1
-20   -20.1   -20.1   -20.2
-30   -30.2   -30.1   -30.2
-40   -40.1   -40.1   -40.3
-50   -50.0   -50.0   -50.2
-60   -60.2   -59.9   -60.4
   
Oh I forgot to test the input impedance, I'll do that next.

ch_scr:

--- Quote from: xrunner on October 29, 2023, 12:00:04 pm ---
--- Quote from: edpalmer42 on October 29, 2023, 02:49:30 am ---Looks good, xrunner, but I have to admit that I'm worried about those surface mount resistors.  They have no physical strength ...

--- End quote ---

Oh now ... it's not true that they have no physical strength. They have a physical "strength" x greater than zero and less than Max. We don't know what "x" is. How hard is it to crack one in two? I have no idea but they don't seem too frail. I've held them with small pliers and tweezers and they don't seem delicate for their size at all.
(...)

--- End quote ---
From my experience, what breaks (or rather rips off) is usually the metallized termination on the ends, not the ceramic carrier itself. The lever on the metallized end is quite large if you have the part soldered down to something solid with it's end sticking up.
In a carefull home shop you should be fine with it, but if one were to knock this around daily I'd guess one of them might break from the shock loads, from the looks I'd mostly be worried about the ones going to the diodes, with their rigid mounting on both ends. Would be interesting to mount this to a shaker table to see what actually breaks  :-DD
I suspect mini- or microMELF components to be more rigid (regarding their terminations especially) than flat SMD's and that might make them more suited for such a repair.
With all that said, good job on the repair nonetheless!

xrunner:

--- Quote from: ch_scr on October 30, 2023, 08:16:33 am ---With all that said, good job on the repair nonetheless!

--- End quote ---

Thanks for your comments.

Here's a microscope pic of several items for comparison.

From top to bottom -

SMD 1206 zero ohm
original 100 ohm Boonton part
Same as above
original 160 ohm Boonton part

The 1206 part is very close to the same length as the resistors, which is the reason I chose that dimension SMD.

The original problem was that one of the 100 ohm parts (red part) was cracking loose right at the solder joint. Why this happened we can't say for sure. However, these parts are decades old and I'd bet money they haven't been touched or repaired since they left the factory. Only the original damaged part was going to be removed and replaced. However, they were so delicate that they just fell apart at the ends (see red parts in pic). Even the metallic coating came off.

Not to stop there, a 160 ohm part (tan resistor) had one end of it crack off. Basically the sensor was at it's end-of-life. After what - 3 decades, it needed to be re-built or tossed. What caused the degradation in reliability? Was it banged on a table numerous times or were the parts the wrong choice from the beginning (for long-term reliability). I know it was in the hands of Ham radio operators for some time, so draw your own conclusions there.

The point is, the original parts Boonton selected, and the original way Boonton engineers told the assembly line workers to construct the center area of the sensor (the soldering) didn't fare all that well in the long run. What I've done is either going to last for a little while (subjective time) or a long while (subjective time). I don't abuse equipment so I'm guessing a long while (years) but we shall see. I'll test it at least once per year and report if if fails.

Kosmic:

--- Quote from: xrunner on October 29, 2023, 12:00:04 pm ---A 41-4B sensor and cable for $60. But one of the connector pins has nothing inside. How well do you think it works? The parts are listed as used which means they works correctly but it's not new. I messaged the seller but no reply yet ...

--- End quote ---

The pins are hollow, and as Ed said, it's not required for the solder to go through up to the tip. As long as the wire is soldered correctly to the pin.

I got some Boonton cables here and some of them are exactly like that.

Navigation

[0] Message Index

[#] Next page

[*] Previous page

There was an error while thanking
Thanking...
Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod