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3 жыл бұрын

In this episode Shahriar repairs an IFR (Marconi) 5GHz programmable attenuator capable of reaching a maximum of 130dB attenuation in 1dB steps. The Instrument does not power on and a teardown reveals some missing components inside. After replacing the missing component, the instrument powers on but the S-Parameters show that the mechanical attenuators have serious contact problems. Finally after cleaning the attenuator contacts, the instrument is fully operational. The unit is used to measure the performance of the Keysight MXR at very low input signal powers.
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Пікірлер: 57

@Thesignalpath 3 жыл бұрын

*Please note that the two attenuator modules are not identical. They are used in sequentially and in conjunction to achieve 1dB steps across the entire 130dB variable range. This is one of the main advantages of this instrument to provide small steps and very large range.*

@Ziferten 3 жыл бұрын

Man, you forgot to say "FIIRRRSST!"

@w2aew 3 жыл бұрын

Interesting repair - it seems the first test of any of this high frequency equipment should be to see if you've got a low-pass problem - seems like a theme! Nice repair and experiments.

@Thesignalpath 3 жыл бұрын

Hehe… By the way, I’d like to repeat the sensitivity experiment with the 6B and the demodulation software. When do you think that would be available?

@w2aew 3 жыл бұрын

@@Thesignalpath It's available now - I'll be in touch...

@vincei4252 3 жыл бұрын

Full bridge rectifier made me laugh. You need to show Mehdi's face every time you say "Full Bridge Rectifier" :)

@danmenes3143 3 жыл бұрын

When I saw that DC wasn't getting through, I was sure the issue was going to be another bad front panel connector.

@Thesignalpath 3 жыл бұрын

Glad that it was not!

@FlyingShotsman 3 жыл бұрын

Thanks, Shahriar. As a hobbyist with little RF knowledge, I'm always fascinated by your tear-downs, repairs and experiments. You must have one of the most well-equipped and valuable home electronics/RF labs on earth, but what do you use it all for? Are you satisfying your own hobby interests, developing products, or do you bring work home that you can't reveal publicly? Any chance you could show us how such a mind-boggling home lab is actually used, beyond eBay repairs? Looking over your shoulder through a full project development would be awesome. Cheers!

@TheFool2cool 3 жыл бұрын

"Be careful cleaning this" Doesn't show him cleaning it. This would be such a useful step to observe for those of us in industry who have never been taught these techniques.

@amciaapple1654 3 жыл бұрын

Exactly

@gorak9000 3 жыл бұрын

If you're in "industry", just buy another one, and let the broken one trickle down to us mere mortals who can't afford to pay full price for RF test equipment, but have the time to fix the broken stuff.

@TheFool2cool 3 жыл бұрын

@@gorak9000 please tell me you're a troll, do you think all of the electronics industry is just awash with money, some of our kit costs as much as a small family home and you think we're just throwing it away?

@djmips 3 жыл бұрын

Your teardowns are the best because you _actually_ fix them a lot of the times!

@kcmichaelm 3 жыл бұрын

This one was so great, and so approachable. I love the variation between the technical-heavy videos and the ‘simpler’ mechanical fixes like this. I’m very happy to support this type of work through the Patreon!

@PapasDino 3 жыл бұрын

Always enjoy your repairs, well done!

@Thesignalpath 3 жыл бұрын

Glad you like them!

@DrTune 3 жыл бұрын

I wasn't watching the video when you said "full bridge rectifier" but I knew enough to rewind a few seconds and look for a visual electroboom reference ;-)

@BruceNitroxpro 3 жыл бұрын

Dr Tune , That was a low blow! ROFLMAO

@DrTune 3 жыл бұрын

@@BruceNitroxpro it's pretty much a requirement of any electronics vlog to honor the meme

@BruceNitroxpro 3 жыл бұрын

@@DrTune , I guess I should say that Electroboom is da man! I thought the laughter said that, I guess not so well!

@hnasje66 3 жыл бұрын

The frequency can be used to read the calibrated attenuation value at that frequency (from display or Ieee interface). If you switch on "corr mode" it will try the set att value as close as possible for the given frequency. E.g. the display will show 100dB but internally it will set 99dB as that is closer to 100dB for the given frequency.

@BruceNitroxpro 3 жыл бұрын

Innas cable guy , Just out of curiosity... you knew this how?

@hnasje66 3 жыл бұрын

@@BruceNitroxpro i used this attuator long time ago testing e.g. RF amplifiers

@BruceNitroxpro 3 жыл бұрын

@@hnasje66 , Aha... this is a very lovely instrument and has great specs. I wonder how much it cost back in the day?

@pastahajianpour5607 3 жыл бұрын

The design of the PSU and the logic board is very similar to my Marconi Instruments 2435 2GHz frequency counter. Cool!

@tchiwam 3 жыл бұрын

My personal mechanical attenuator failures are: little O rings that dampens the movement. The pin might not be at the right place in the tiny slit Dirty contacts , most frequent Only once I had a die that did not work.

@worroSfOretsevraH 3 жыл бұрын

Would have been helpful to see the procedure you took to clean those contacts.

@mohinderkaur6671 3 жыл бұрын

phool-bridge rectifier!

@jaa93997 3 жыл бұрын

If it's missing a FUUUULLL BRIDGE RECTIFIEEEEEER then it belongs to Electroboom 😉

@tuugem8571 3 жыл бұрын

Could you please include in your tests something that tests the device way past their rated frequency range? There are so many quality items on the market that behave very well even outside of their specified parameters. It would be very interesting to see which devices work well at higher frequencies, and which ones don't work well at all. Considering all of these devices are purchased used, it would be so helpful to get the most out of them. Like this attenuator, I wonder if one could go do 9Ghz and have it still be usable, etc. Thank you.

@samfedorka5629 3 жыл бұрын

If it's possible to damage some devices by putting too high frequency into them, then you'd end up having to test them to failure to find their performance outside their rated frequency. Another possible issue is that they might perform differently at different signal levels and frequencies and it would be too time consuming to characterize their performance across all parameters. That said, I'd love to see how they perform at higher frequencies, especially if it has a linear rolloff, you could find the -3dB point and use that to calibrate out the additional attenuation from the device on top of the attenuation you program.

@aardvark2zz 6 ай бұрын

Aren't these moveable strip lines more operating like CPW (Coplanar waveguides) with side grounds !!?

@aardvark2zz 6 ай бұрын

Instead of coaxial due to moving center conductor !!?

@paulpaulzadeh6172 3 жыл бұрын

just wonder what is the algorithm of equalizer parameter , how we do know to adjust those parameter for equalizer ?!

@3ffrige 2 жыл бұрын

That was an amazing video! How did you clean the attenuator contacts? Can you use something like Deoxit?

@metasequoia12 3 жыл бұрын

Great video! what cleaner did you use?

@dtiydr 3 жыл бұрын

0:12 I really would like to know what dumpsters you have.

@jack_brooks 3 жыл бұрын

I'm guessing the full bridge rectifier was scavenged after the instrument was found to not be working.

@Thesignalpath 3 жыл бұрын

Yes, it is likely.

@samfedorka5629 3 жыл бұрын

@@Thesignalpath I still find it to be odd. You can get a 15A rectifier for $1, and I can't imagine the one in this instrument to be that big. Perhaps they needed something right away?

@thomasw6169 3 жыл бұрын

Not another of those simple faults 😀 (The rectifier)

@witeshade 3 жыл бұрын

Does the freq button do anything?

@amciaapple1654 3 жыл бұрын

I'd like to know that, too.

@benmodel5745 3 жыл бұрын

The people have a right to know!

@Thesignalpath 3 жыл бұрын

It did nothing! :)

@witeshade 3 жыл бұрын

@@Thesignalpath that's a shame. I was hoping they'd at least snuck a free simple frequency counter or something in there!

@KF7JO 3 жыл бұрын

@@Thesignalpath It's to compensate for the actual loss at a given frequency, since the frequency response isn't completely flat from DC to 5 GHz. For example, setting the programmable attenuator to 10 dB may require setting 9 dB of face value with 1 dB of additional internal loss.

@homersimpson6985 3 жыл бұрын

What causes the contact to fail? Carbon buildup or pitting?

@Thesignalpath 3 жыл бұрын

Just aging. It not perfectly hermetically sealed.

@jonka1 3 жыл бұрын

I'm curious as to why spraying contact cleaner would ruin the attenuator. Would you please explain why.

@mihaiachim5299 3 жыл бұрын

5:05 I don't think that Philips capacitor will die in the next 20 years (Vishay now if I look at their design that looks identical) :P

@JimGriffOne 3 жыл бұрын

Are the attenuator units using binary values to produce all the attenuation steps? (MSB-LSB).

@KF7JO 3 жыл бұрын

Binary steps would allow the minimum number of fixed attenuators and switches, but not necessarily the minimum number of switch actuations, since that's a wear item, a point of failure, and also may maximize tolerance stack up errors where the insertion loss differs by the face value. It's also helpful for the engineer to know where the bigger attenuator steps are, since the errors are larger when switching those in and out. It's convenient for us base 10 creatures to have those large steps occur on 5 dB or 10 dB boundaries.

@morto360 3 жыл бұрын

Is that display you attached just a touchscreen or a whole pc? I am looking for a small device like that if its just a touchscreen and no pc build in. Please let me know what it is and where i can geht it. Thanks!

@Thesignalpath 3 жыл бұрын

Yes, just a small LCD. Just search on Amazon for 7” LCD.