[Collins] KWM-380 Fix
David Knepper
[email protected]
Thu, 25 Dec 2003 13:16:00 -0500
Here are the details on my fix:
KWM-380 unlocked and started beeping.
Discovered that TP 1, 2, 3, on A5A1 did not have the correct voltages.
These test points are not the same ones on A5A2 board to set the reference
voltages for the synthesizer. These are merely voltage reference test
points that are clearly marked on the top side of the board.
I took an ohmmeter reading and, yes, there was almost a dead short at 100
ohm resistor on A5A2. The voltage buss from the 28 volt regulator next to
the power supply board (this is the one that has the enclosed can) goes to
the frequency synthesizer variable referency frequency loop on synthesier
board A5A2.
C-61 or a 4.7 mfd/30 volt yellow electrolytic was shorted. This cap is on
the input going to the 18 volt and 30 volt regulator circuitry.
Now the 380 is back on the operating desk after a year of sitting in the
corner.
File this one away somewhere if you own a KWM-380 and the synthesizer
unlocks. I trust that I explained this correctly.
Here I was thinking one of the chips but it turned out to be nothing more
than a simple 10 cent capacitor!
Dave, W3ST
Secretary to the Collins Radio Association
Publisher of the Collins Journal
www.collinsra.com