================================================== ==
Disclaimer:
This post is for educational purposes only, and no guarantees are
offered. Proceed at your own risk.
================================================== ==

Some of you may have purchased the Palomar Elite 300 amp currently
being sold on Ebay and various other places. If you have not bought
one yet...don't! The amp has several major design flaws. If you do
have the misfortune of owning one of these then the following post may
be of interest.

-----------------------------------------------------------------------------------------------
How to fix two design flaws in the Palomar Elite 300 amp.

Design flaw # 1.

The Palomar Elite 300 amp is a class C amplifier. In a nutshell that
means your transmit audio on sideband will become distorted as soon as
you turn the amp on. No amount of mic adjusting, SWR tuning, cable
swapping, or anything else will fix it. The problem is in the amp
itself. To fix the problem you or a qualified technician will need to
bias the amp for class B or AB1 service. The instructions below will
show you how to fix your amp. All you need is basic soldering skills,
and a minor understanding of electronic parts.

Here is the bias fix.
------------------------------------------------------------------------------------------------------
You may need to remove the Palomar Elite 300 from the housing to do
this mod. I took off the front face plate, removed the four allen
screws holding the heat sink to the two final output transistors,
removed the screws holding the two female coax connectors from the
back of the plate, and then took the little plastic holder from around
the main DC wires. The unit slides out of the front at that point.

1) Look at the top of the circuit board from the front of the amp.

2) To the left of the smaller input broadband transformer there is a
ferrite bead.

3) Unsolder the farther leg of the ferrite bead which is closest to
the back panel. Leave the other leg where it is. If you look at the
back of the circuit board the leg you want to unsolder is the leg that
goes to ground.

4) Solder a silicon diode with the cathode (the line) facing away from
the ferrite bead to the leg of the ferrite bead you previously
unsoldered. I used a Radio Shack 1000 PIV 2.5 amp silicon diode -
catalog # 276-1114.

5) Solder the cathode side of the diode (the white line) facing down
in the little hole the one leg of the ferrite bead was soldered in.

See the picture at;

http://www.shadowstorm.com/cb/Paloma...Bias-fix-2.jpg

6) Get a 100uh RF choke from Radio Shack (Catalog #: 273-102).

7) Solder one end of the RF choke to the solder covered side of the
larger output broadband transformer.

See the picture at;

http://www.shadowstorm.com/cb/Paloma...Bias-fix-1.jpg

8) Solder a 100 ohm 1 watt resistor to the other end of the RF choke.
I used a Radio Shack metal oxide resistor - Radio Shack catalog #
271-152.

9) Solder the other end of the 100 ohm resistor to the junction where
the ferrite bead and the diode you previously soldered meet. If the
resistor gets too hot during transmit Radio Shack carries a 10 watt
100 ohm resistor, but it is kind of big.

10) Make sure none of the exposed wire from the parts you added
touches the bottom, top or sides of the metal case.

11) Re-assemble the Palomar Elite 300.

10) You're done!

Your sideband tranmit audio with the Palomar Elite 300 should now be
clear.

--------------------------------------------------------------------------------------------------------

Design flaw # 2.

On another issue, the Palomar Elite 300 does not filter RF from the
B+ line, so the DC power leads act like an antenna just like the
regular antenna. The RF running up the DC power chord kept tripping
out my power supply until I wrapped the DC power chord around a large
ferrit core just outside of the amp chassis. (Radio Shack 273-104) .


-----------------------------------------------------------------------------------------------------------

There are other design flaws as well (like a nasty impedance mismatch
for both broadband transformers), but these are the only two I have
attempted to fix so far.

A stupid design, poorly built. I love it. Maybe the impedence msimatch
will blow up a few keyclown radios. That's a good thing. Shane, you
should quit flipping your wrist for these queens.

Man thats a great post, good going.

Jay in the Mojave


Scooby Don't wrote:

================================================== ==
Disclaimer:
This post is for educational purposes only, and no guarantees are
offered. Proceed at your own risk.
================================================== ==

Some of you may have purchased the Palomar Elite 300 amp currently
being sold on Ebay and various other places. If you have not bought
one yet...don't! The amp has several major design flaws. If you do
have the misfortune of owning one of these then the following post may
be of interest.

-----------------------------------------------------------------------------------------------
How to fix two design flaws in the Palomar Elite 300 amp.

Design flaw # 1.

The Palomar Elite 300 amp is a class C amplifier. In a nutshell that
means your transmit audio on sideband will become distorted as soon as
you turn the amp on. No amount of mic adjusting, SWR tuning, cable
swapping, or anything else will fix it. The problem is in the amp
itself. To fix the problem you or a qualified technician will need to
bias the amp for class B or AB1 service. The instructions below will
show you how to fix your amp. All you need is basic soldering skills,
and a minor understanding of electronic parts.

Here is the bias fix.
------------------------------------------------------------------------------------------------------
You may need to remove the Palomar Elite 300 from the housing to do
this mod. I took off the front face plate, removed the four allen
screws holding the heat sink to the two final output transistors,
removed the screws holding the two female coax connectors from the
back of the plate, and then took the little plastic holder from around
the main DC wires. The unit slides out of the front at that point.

1) Look at the top of the circuit board from the front of the amp.

2) To the left of the smaller input broadband transformer there is a
ferrite bead.

3) Unsolder the farther leg of the ferrite bead which is closest to
the back panel. Leave the other leg where it is. If you look at the
back of the circuit board the leg you want to unsolder is the leg that
goes to ground.

4) Solder a silicon diode with the cathode (the line) facing away from
the ferrite bead to the leg of the ferrite bead you previously
unsoldered. I used a Radio Shack 1000 PIV 2.5 amp silicon diode -
catalog # 276-1114.

5) Solder the cathode side of the diode (the white line) facing down
in the little hole the one leg of the ferrite bead was soldered in.

See the picture at;

http://www.shadowstorm.com/cb/Paloma...Bias-fix-2.jpg

6) Get a 100uh RF choke from Radio Shack (Catalog #: 273-102).

7) Solder one end of the RF choke to the solder covered side of the
larger output broadband transformer.

See the picture at;

http://www.shadowstorm.com/cb/Paloma...Bias-fix-1.jpg

8) Solder a 100 ohm 1 watt resistor to the other end of the RF choke.
I used a Radio Shack metal oxide resistor - Radio Shack catalog #
271-152.

9) Solder the other end of the 100 ohm resistor to the junction where
the ferrite bead and the diode you previously soldered meet. If the
resistor gets too hot during transmit Radio Shack carries a 10 watt
100 ohm resistor, but it is kind of big.

10) Make sure none of the exposed wire from the parts you added
touches the bottom, top or sides of the metal case.

11) Re-assemble the Palomar Elite 300.

10) You're done!

Your sideband tranmit audio with the Palomar Elite 300 should now be
clear.

--------------------------------------------------------------------------------------------------------

Design flaw # 2.

On another issue, the Palomar Elite 300 does not filter RF from the
B+ line, so the DC power leads act like an antenna just like the
regular antenna. The RF running up the DC power chord kept tripping
out my power supply until I wrapped the DC power chord around a large
ferrit core just outside of the amp chassis. (Radio Shack 273-104) .


-----------------------------------------------------------------------------------------------------------

There are other design flaws as well (like a nasty impedance mismatch
for both broadband transformers), but these are the only two I have
attempted to fix so far.