[Amps] Alpha 9500 questions

GWP gm5bkc at gmail.com
Mon Jul 27 11:58:31 EDT 2020

Some Alpha 9500 info:

Alpha 9500 Tubedeck Blower Types by Serial Number:
950012400632  Last old blower (AC Motor)
950012400633 and on   New Papst DC blower
The chassis sheet metal is significantly different (as well as blower speed
change circuits) and a Papst DC blower CAN NOT be installed in an amp with
the AC blower.

The middle 4 digits of the serial number are date code, year and week of

All 9500 amps have a muffin fan pushing air into the rear of the amp.

Hall Effect Sensor replaces a pot for sensing bandswitch position.  Amps
built 2014 and later, or any repaired 2015 or later should already have the
Hall sensor.

A fuse was added to the 40v cathode bias supply to protect PCB traces if a
tube shorts the cathode internally.  Amps built 2015 and later, or any
repaired 2015 or later should already have the 40v Fuse Mod installed.

HV metering resistors were changed to higher wattage resistors.  They are
usually changed (blue parts) during repairs if the old type (brown parts).
In the 9500 the HV reading is used to verify that the correct Mains AC tap
was selected, drifting HV reading may cause a fault.

Early 9500 amps have a square shaped power transformer.  No exact dates or
serial number for the change to a toroidal wound transformer as they were
installed as production of the transformers changed.  The cylinder-looking
toroidal transformer raised the HV about 100v, it does not give the 9500
significantly more output power.

Main Controller firmware can be updated via the USB port, the other 4 PICs
have to be updated via programming headers on the PC boards.

The firmware versions can be checked without turning the amp on with a
terminal program (like RealTerm) on usb port.  No need for any special
software.   Just watch the sign on banner that comes out when the amp is
plugged in, the 5 firmware versions are in the "banner".

Firmware update instructions are on the Alpha web site, and firmware files
are available via email.  It is NOT recommended to update only the Main
Controller if the other PICs are very low versions because the amp won't
work better, and may not work as well.  Firmware 3.03/3.04 are the latest
numbers in all 5 PICs.

Glenn AE0Q
Alpha RF Systems

On Sun, Jul 26, 2020 at 11:21 AM Bob <n612dw at gmail.com> wrote:

> Thinking of acquiring a 9500. but first need to learn a few things. someone
> help me with these questions?
> What are the "updates/upgrades have been done" that I often see along with
> a
> "for sale" ad??   it seems to include (but not limited to):
> What is/are the xfmr/blower/hall effect upgrades made and why are/were they
> done?  What do they fix/prevent?
> What others besides the above are out there?
> When did they begin including these into production, at what serial
> numbers/years?

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