I forgot to note in my first message that I did very recently unplug, clean,
and replug all the plugs accessible via the under side removable panel. I have
not yet worked on all the other plugs, but will. Some black could be rubbed
easily off some of the plugs. My next step is to unplug/replug all the
connectors again. Also, to hook it to a computer and follow that line of
diagnostics, too. I see that the 9500 is advertised as now designed without
all those plugs. I really doubt that the 87a ones can actually wear out, but
it looks like my unit will need this cleaning frequently. Clearly a design
flaw that works for the first few years. Manufacturers forget that ham rigs
never go away ...they are simply traded off to a ham with less money. I
believe in the 20 year refrig, the 10 year automobile, and the 40 year ham
radio................. please, stop laughing, readers. Thanks to all
respondents.... I will keep reporting until the problem seems licked and report
that
too. 73,
Charles Harpole
k4vud@hotmail.com
> From: VE1DT@infinichron.com
> To: k4vud@hotmail.com
> Subject: [Amps] A intermittent 87a
> Date: Sun, 22 Jan 2012 12:00:19 -0400
>
> Charles,
>
> I found this article about 87A's and fault 20 that might be useful to you.
>
> http://asktheham.com/node/51
>
> --
> Gerald Boutin, VE1DT
>
>
>
> Alpha 87A Fault 20 or 18
> Sat, 12/04/2010 - 21:03 - administrator
>
> We have found that reseating the connectors on circuit boards may stop the
> erroneous filament current readings.
>
> Stand the 87A on the right-hand side and remove the plate under the
> tube-deck. Unplug and carefully reconnect the plugs inside the tube deck.
> Also reseat the orange connector on the LVPS (Low Voltage Power Supply)
> directly in front of the power transformer, and just above the
> bottom orange connector that is on one of the transformer cables. Use Caig
> DeOxit contact cleaner (available at Radio Shack) on those connectors to
> ensure a better contact.
>
> Reseat the two large red connectors on the top edge of the control board.
> They are accessable through the slot in the top-right side of the front
> sub-chassis (behind the LED bargraph displays).
>
> The Fault 20 may indicate a bad tube or a metering resistor that has aged
> and changed value. With a computer connected to the 87A serial port you can
> use the following commands to see what the filament current is (they are
> always followed by the ENTER key):
>
> Type EXT ON (ENTER) , this puts the amp in the 'factory mode' and will let
> it accept the next command.
>
> Type ADS FIL (ENTER) numerous times and record the readings. This will give
> you the filament current. It will read some filament current even when the
> 87A is turned off, this is normal and is not a 'real' number because the
> tubes are turned off. The fault limit is 4.0 amps.
>
> When you are done testing, type EXT OFF to turn off the 'factory mode' so
> that no wrong commands will accidentally be written to the microprocessor.
>
> Once you have completed this process, email the factory with your results
> and for further instructions on possibly changing the filament current
> limits in the amplifier EEPROM
> Forums:
> Alpha 87A Entries
>
> Log in or register to post comments
>
> Thu, 12/09/2010 - 02:23 - mollyh
> Fault 20 on the 87A
>
> Note that although the formal resolution above also talks about a possible
> tube problem - in my 10+ years working directly with Alpha amps I have yet
> to see a Fault 20 that is caused by a bad tube. Cleaning the connectors as
> described above will give you anywhere from 6 months to 2 or 3 years more
> 20-free operating. Eventually you will need to get the connectors
> changed......
>
>
>
>
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|