Eddy,
I wasn't sure whether you were counting the LEDs from the left or right (the
correct way is to count from the right, as in binary arithmetic.) If you are
counting from the right, the LEDs would look like this ("+" indicates a
blinking LED and the "o" indicates a dark LED):
oo+o+
This is fault #5, Hard, "Plate voltage abnormally low." This is a hard
fault, which shuts off the power.
If you are counting from the left, the LEDs would look like this:
+o+00
This is fault #20, Soft, "Filament current greater than 3.5 amp. Possible
shorted filament." This is a soft fault, where the amp falls into standby
but power stays on.
>From your description, it sounds like the amp stayed on, so it must be fault
#20.
It's hard to speculate about a cause -- this is a very complex amp. It could
be a tube problem (unlikely since you changed the tubes), a filament
transformer problem, a problem with the ICs that detect filament voltage, or
a problem with the power supply for those ICs.
Since the problem only happens on 10M, it's possible that you have an RFI
problem. I once had some mysterious faults on 10M that I traced to RF on the
key line. I cured it by adding .01uf bypass capacitors to the key line from
the transceiver to the amp. You could test this by replacing the key line
with a shorting plug in the amp's KEY IN jack, then keying the transmitter.
73, Dick WC1M
To: <amps@contesting.com>
> Date: Mon, 19 Mar 2001 07:20:32 +0100
> From: "Eddy Jespers" <ejespers@wanadoo.be>
> Subject: [AMPS] Alpha 87A Fault Indications
>
> I lost my Alpha 87A manual, and have a fault indication. On 10m only, the
> amp goes in protection showing LED 1 and 3 blinking.
>
> I changed the tranceiver, antenna measured the line voltage, enven
> changed the tubes, the fault occures when the output is more than
> 300 W on 10 m only. On all other bands the amp runs fine.
>
> Can somebody look up this fault in a manual ? or
> can somebody send me the different fault codes from the manual ?
>
> Thanks,
>
> best 73's
> Eddy ON7UN
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