[Amps] Alpha fault 17

[Dick Green WC1M]

Some additional points:

- You may not be able to see evidence of arcing until you remove the choke.
- You may need to replace (rewind) the coil. Just count the turns and use
the same gauge/type of wire
- When my choke coil started arcing, I didn't get fault 17. I got faults 8
and 9 (and 1, I think).
-  This was evidence that the arcing damaged one of the transmit PIN diodes,
which I had to replace.

Don't use the amp until you attend to the choke coil. You don't want to risk
damage to the PIN diodes, which are expensive.

73, Dick WC1M
 
-----Original Message-----
From: K2CB [mailto:k2cb at comcast.net] 
Sent: Friday, December 9, 2016 12:54 AM
To: ve6jy.1 at gmail.com
Cc: Amps at contesting.com
Subject: Re: [Amps] Alpha fault 17

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