IFR am/fm-1200: Two-way radio repair, not yet (update 5 more pictures)

IFR am/fm-1200 arrived on time as expected but the IFR am/fm-1200 has more issues than the seller lead me to believe. I am still hopeful that I can figure this one out but at thispoint I am a little bit frustrated. I am still looking through the various boards and changing out the fuses. Maybe I will get this service monitor up and running soon… maybe not.

Edit 1 (1 hr in): 3 fuses later the unit is up and running in a basic FM narrow receive mode. Audio is good and receive seems to be on frequency. Scope seems to be having an issue and I have found multiple broken parts. The IFR am/fm-1200 is missing the antenna, AC and DC power cords, operation manual (3 ring binder is present but manual has been removed). It does have the Illustrated Parts Catalog for the fm/am-1200 communications service monitor.

Edit 2: Well, was able to tune a few radio but have no spectrum analyzer working.  When I turn on the scope I get a checksum error and then a memory error.   I sent an email to Kurt Graber at KG electronics but he is a business and suggested I ship it in.  Not much help there I guess unless I just want someone else to do it.  I will take the scope out and take a look at the power control board for it.  Surely I will find the melted part (at least one would hope…).  So for now the IFR FM/AM-1200 sits here on my desk, is able to do a variety of things but is without scope.  The scope on the IFR communications monitor is something I was looking forward to using so this is a pretty big set back. 

Sidenote: Sent an email to the person who sold me the device, they claimed another issue was “only” thing wrong with it.  Feeling a little burned at the moment, no pun intended. Now off to find the burned parts…..

ifr am/fm-1200 scope power supply board burned resistorifr am/fm-1200 scope power supply board burned by resistorEdit 3: Found the issue in the power control board of the IFR am/fm-1200. Now to decypher the results as my schematics do not match but I am 99% sure of the resistor in question… anyway here are the pictures, note the heavy board burn where the resistor on the ifr am/fm-1200’s spectrum/scope power supply shorted.  I imagine the smoke would have been a dead giveaway that the service monitor was in need of some internal love.  

Edit 4: in looking at the entire board and tracing out the current flow I have found more suspect parts, in particular is a irf520 that seems to be shorted. I am reviewing the spec sheet for that part and will be running some more tests.  Pictures are here and you can see the heat bubble in the pcb board where that resistor had overheated and failed.  following the schematics of the ifr am/fm-1200 I found that the source of the overvoltage in the resitor was the irf-520.  It is reading a short(see pictures).

Another view of the irf-520 is shorted and burned on the scope power supply in my ifr am/fm-1200

this spectrum scope power supply pcb board got hot enough to bubble. damage is still being assesed

irf-520 is shorted and burned on the scope power supply in my ifr am/fm-1200

  Thank you for all the great support and emails!  They have been great and very helpful!  Keep them coming!

more to come

P.S.  If you have any ideas or have one of these yourself, I would love to hear from you!!!

Thank you

more to come soon…

2 thoughts on “IFR am/fm-1200: Two-way radio repair, not yet (update 5 more pictures)”

    1. The mic seems to be an elusive part. The last one I saw on ebay went for more that 80 dollars US(Feb. 2011). I will check a few places and see if I can get you a better answer than just a old price quote… I will check into how you can get both the mic and the antenna and let you know

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