Author Topic: EraSynth Micro Damaged Output  (Read 443 times)

0 Members and 1 Guest are viewing this topic.

Offline Mechatrommer

  • Super Contributor
  • ***
  • Posts: 10298
  • Country: my
  • reassessing directives...
EraSynth Micro Damaged Output
« on: September 02, 2020, 06:51:17 pm »
long story short, bought Dec last year, the output stage of my lightly used EraSynth Micro is dead... L4 L5 L2 (attachment 1) got pretty hot and then L5 got damaged (opened at 1.7Kohm resistance), now everything is cold but no output... possibility is GVA-83+ got damaged, but how i'm not sure, its AC coupled and i got the output on 50 ohm termination shorted while probing, but its only for a brief moment i can see it on DSO. its still survive during the probing until i turned it off, few second later i turned it on and no more output... opening it up everything is hot, and while probing, L5 burnt up as already mentioned...

1) is it possible to damage an AC coupled MMIC by shorting the other end for a short moment?

back calculating the output level, max output is 15dBm, thats 3.55Vpp according to my android apps here (RF Power Converter), GVA-83+ gain is 20.5dB at 100MHz, so at its input there should be 3.55V / (10^(20.5/20)) = 335mVpp of signal, but i'm not seeing that kind of level either. its from another AC coupled MMIC stage GALI-2+ (AMP1 in 2nd attachment) it didnt go that hot and its still have Vdc on the output indicating biasing still working, but no 335mVpp on the output, there's about 50mVpp signal though i can see on my DSO jumping about. since its gain is 16.2dB at 100MHz, at its input should be 335mV / (10^(16.2/20)) = 52mVpp. i sort of see that outputting from synthesizer LMX2572 + RF ATTN (F2250), so i guess LMX2572 and F2250 are ok? since AMP1 (GALI-2+) shows no gain, is it safe to say its damaged too? but how? it doesnt go hot and doesnt directly interact with user like on the output stage (AMP2). what sort of possibility of all of this unfortunate?  :'(

ps: i'm contacting the EraSynth support, while waiting for the answer, may i ask here as well thanks.
« Last Edit: September 03, 2020, 12:55:17 am by Mechatrommer »
It's extremely difficult to start life.. one features of nature.. physical laws are mathematical theory of great beauty... You may wonder Why? our knowledge shows that nature is so constructed. We simply have to accept it. One could describe the situation by saying that... (Paul Dirac)
 

Offline jan48

  • Newbie
  • Posts: 3
  • Country: il
Re: EraSynth Micro Damaged Output
« Reply #1 on: September 07, 2020, 09:08:43 am »
The inductors getting hot indicate that your AMP2 has shorted to GND. Its input impedance is now very low and your AMP1 is  feeding an approximate short instead of its nominal 50 ohm load. This would explain the low signal level that is present at AMP1 / AMP2 junction. Try to replace the damaged inductor and AMP2 . And YES !  It is possible to damage RF devices by AC coupled shorts to ground due to sudden changes in RF impedance.
 
The following users thanked this post: Mechatrommer

Offline Mechatrommer

  • Super Contributor
  • ***
  • Posts: 10298
  • Country: my
  • reassessing directives...
Re: EraSynth Micro Damaged Output
« Reply #2 on: September 07, 2020, 10:05:54 am »
you are very spot on.. you must be familiar with this kind of RF design and thanks for chiming in after these few days of zero interest/reply. refering to the attached pic, is internal of the GVA-83+ MMIC (almost all MMICs if not all, are similar like this) i checked with DMM, RF-OUT to GND is shorted near 0 ohm (R4), but RF-IN is about 800+ ohm to GND, so the MMIC input is not shorted, at least when its turned off, but i guess you are right, when its turned on, the T1's emitter will meet the short hence its base (MMIC's input). anyway i concluded (fixed) the repair that AMP2 is indeed damaged, with advice from Mr Adnan of EraSynth Inc, i removed the AMP2 and after that i can see some -5dB signal coming out of AMP1, luckily its not dead. GVA-83+ replacement part is on its way now from Russia, and i also ordered GALI-2+ (AMP1) from China just in case for future repair or other RF project. very difficult to find the parts online (or too expensive $9/chip), digikey and lcsc dont stock them, Mouser cant send to my country (military grade potential of terrorism i dont know :palm: who cares i have more advanced 8GHz ERA-1SM+ in stock ::)), while waiting, i temporarily installed SOT-89 compatible HMC480 (with recommended biasing) into my EraSynth Micro, and now it can output somewhere at 9dB max.. cheers. edit: and i also modded the EraMicro PCB by adding a heatsink underneath (as recommended by datasheet) so the MMICs will not get very hot later...
« Last Edit: September 07, 2020, 10:12:47 am by Mechatrommer »
It's extremely difficult to start life.. one features of nature.. physical laws are mathematical theory of great beauty... You may wonder Why? our knowledge shows that nature is so constructed. We simply have to accept it. One could describe the situation by saying that... (Paul Dirac)
 


Share me

Digg  Facebook  SlashDot  Delicious  Technorati  Twitter  Google  Yahoo
Smf