On Fri, 26 Sep 1997 07:41:41 -0400 (EDT) Dave Hockaday <wb4iuy@ipass.net>
writes:
SNIP
>A couple of nights ago, I was on 40m CW (I think, though I may have
>been on
>ssb trying to work the ZK1). A loud "SNAP!" came from inside the case.
A typical AL-82 happening.
>The
>amp continued to work OK, but now my idling current is up to 325 ma.
>(from
>the normal 75ma CW/150ma SSB). The plate voltage is about 3500vdc
>unloaded,
>and about 3300vdc loaded, exactly as it was when I first powered it
>up. The
>SSB/CW switch has absolutely no effect on the idling current, it stays
>at
>325ma while the amp is keyed with no drive.
Check the zeners first but I'm betting the protection diode on the filter
board has failed. Get a large supply for the future. I also bet those
tubes have a nice bright glow.
Now....as to other failed parts.... Inspect the bandswitch and plate
choke for arcs or hot spots. Also measure the suppressor resistors.
Finally, test one tube at a time for idle current.
Trade it in on an AL-1200 or an Alpha 91b.
73 Carl KM1H
>
>The rig I use with this amp only drives it with about 80 watts. After
>the
>"SNAP!", the power output of the amp seems to have increased a little.
>What
>could have failed?
>
>Wow...The amp is only 2 weeks old.
>
>I studied the schematic a bit. I don't think the problem is in the
>metering
>board, especially since the current doesn't change when the CW/SSB
>switch is
>toggled. I guess it's possible that the zeners (ZD1 and ZD2) could
>have
>failed, but isn't it unlikely that they would both fail at the same
>time? If
>the Zeners failed, wouldn't that indicate some sort of momentary
>arc-over in
>one of the tubes??
>
>Thanks
>Dave WB4IUY
>wb4iuy@ipass.net
>
>
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>
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