A shorted tube wouldnt be drawing positive plate current.
Sounds like a gas arc took out the zener and the amp is now zero biased.
Look for a glow in the tubes when in standby mode, maybe all they need is a
good regettering due to a long period of no use.
I wouldnt advise using it until the problem(s) are fixed.
The PS board is fine and MFJ has 270uF replacements in their catalog as used
in their Ameritron amps. Id also replace any equalizing resistors that are
out of tolerance.
Carl
KM1H
----- Original Message -----
From: "Jim W7RY" <w7ry@centurytel.net>
To: "mike stokes" <mike9v@gmail.com>; "Amps" <amps@contesting.com>
Sent: Monday, April 13, 2015 11:52 PM
Subject: Re: [Amps] LK-500 ZB
Sounds like a shorted tube. Is there negative grid current?
73
Jim W7RY
-----Original Message-----
From: mike stokes Sent: Monday, April 13, 2015 12:25 PM To: Amps Subject:
[Amps] LK-500 ZB
Hello
I have a Amp Supply LK-500 ZB and yesterday it made a big bang and blew
both fuses. Now when I power it up the meter says it is drawing about 300
mA while sitting idle. I have performed a visual inspection and there is
no visual evidence of anything being wrong. I bought it used, so it is
uncertain if the power supply has ever been rebuilt. Any thought were to
begin the troubleshooting ? Is the p/s board worth rebuilding or should I
drop in a Harbach replacement board ?
Comments appreciated.
Thanks in advance and 73
--
Mike Stokes
KK9V
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