[Amps] AL80-B fuse F101 blown;step-startnot working?

[Kim Elmore]

If you simply remove the tube and problem persists, it's not the tube. Given what you saw, I doubt the tube is the problem. 

Kim N5OP

"People that make music together cannot be enemies, at least as long as the music lasts." -- Paul Hindemith

> On Nov 28, 2014, at 14:37, "Jim W7RY" <w7ry at centurytel.net> wrote:
> 
> Or a shorted tube will take out the step start fuse and resistors.
> 
> 73
> Jim W7RY
> 
> 
> -----Original Message----- From: Carl
> Sent: Friday, November 28, 2014 12:49 PM
> To: John DiLorenzo ; amps at contesting.com
> Subject: Re: [Amps] AL80-B fuse F101 blown;step-startnot working?
> 
> The first thing Id check is to see if the relay contacts are welded,
> Ameritron uses the wrong contact alloy for high current use. Also check that
> the step start circuit is wired per the manual as Ameritron amps had a
> history of miswiring that could take out the transformer going back to the
> AL-80A and larger amps. Dont expect to find Ameritron issuing a bulletin or
> admitting a problem.
> 
> If the relay is good then disconnect the HV AC from the rectifier circuit.
> If the fuse blows again then the transformer is likely cooked or there is a
> problem on the optional jumper terminal strip.
> 
> Carl
> KM1H
> 
> 
> 
> 
> ----- Original Message ----- From: "John DiLorenzo" <john.dilorenzo33 at gmail.com>
> To: <amps at contesting.com>
> Sent: Friday, November 28, 2014 2:48 PM
> Subject: [Amps] AL80-B fuse F101 blown;step-startnot working?
> 
> 
>> I acquired this amplifier about two weeks ago, and when I received it,
>> neither theforward nor reflected power meters would indicate anything. As a
>> "test", Ireplaced the detector diodes (D114 and D115) with 1N914s as these
>> were diodes I had on hand.  My intent was to see if the meters would at
>> least register something, and if so, order the correct diodes (1N34s).
>> Well that worked,so I ordered the diodes.
>> 
>> They arrived, so I replaced the 1N914s with the correct 1N34s.  With the
>> unit all buttoned up again, I noticed while tuning up, the meter lamps
>> would dim, and the HV would sag significantly.  I wanted to test and record
>> some values when the amp shut down completely; this is what I had to that
>> point:
>> 
>> HV
>> (volts) Ig
>> (mA) Ip
>> (mA)  Standby 3050 0 0  Keyed, no drive 3050 0 0  CW, 5W drive 2700 20 125
>> I discovered that F101 had blown in the amp.  This fuse is in series with
>> the step start resistor, so it seems my step-start was staying in the "low
>> current" mode, and when I keyed the amplifier, this 2A fuse blew as
>> expected.  I'm just not sure what broke.  The diodes I replaced aren't near
>> the rectifying diodes that pull the step-start relay.  Any insight into
>> common failures, where to start looking, or how to debug?
>> 
>> Thanks in advance,
>> John, K8DIL
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