[Amps] Alpha fault 17

[K2CB]

Do a search of the 87A Yahoo group regarding the large L1 choke coil on the RF output wattmeter / pin diode / bypass relay module near the rear antenna jack. Don't quote me on the exact part designation, as I am not at my desk top at the moment, but it is the large green one on that board.

Remove the four screws and shield cover.  You will see a large green wire wound choke coil.  Alpha placed a piece of black foam between the coil and circuit board as an insulator. 

This material is breaking down over time, and causing the coil to arc over to the ground plane of the circuit board. It will get worse over time,  and the fault 17 will occur with less and less rf output power as time goes on.

Remove the choke from the board, remove all the old foam pad, clean off any carbon on the circuit board from the arcing , and install a replacement piece of insulation material.  I used some thin black plastic.  Then reinstall the choke coil.

If you must remove the entire circuit board, be especially careful with the pin diode mounting and associated insulators.  They are somewhat fragile.


If you like, I can send you some pictures I took of the last 87A I repaired with the same problem. The photos are on my desktop. I can send them tomorrow when I get back to my office.

FYI - Credit is due to Brad from Alpha (or whatever their name is this year!) for originally suggesting this as a possible Fault 17 cause. 

Eric
K2CB