Ramsey Q Amplifier salvage

 Yesterday I went to a local electronics store here in Tulsa.  The store has quite a bit of salvage electronics including old tubes and other stuff.  I was looking electronic benchtop components that I could salvage for project boxes. I found three boxes with UHF connectors in the back, which I bought at salvage price.  Opening them up I found a couple of amplifiers that may be useful.  The first is a Ramsey Q Amplifier in what looks like a Radio Shack project box.  The front view is below.  Click to enlarge. 

The RCA connector on the lower right is probably the enable line or for keying.  The switch to upper left is the power switch,  I believe the black push button switch in the lower left is for bypassing the amplifier.   The back view is is shown below and is simply the RF in, RF out, and a post for attaching chassis to ground.

The internal view showing the Q Amp PCB is shown below.  Click to enlarge. 

The amp has some modifications that have been added.  The power connector is wired to a fused pigtail that goes to an external power source.  A temperature sensor is attached to the final transistor heat sink and apparently an overtemperature cutoff circuit has been added, mounted to the bulkhead on the left.  This drives a cutoff relay that's taped to the chassis bottom on the lower right of the photo.  In the upper right of the circuit you can see there's spaces for 3 inductors and 4 capacitors for a 7 pole low pass filter on the RF output before it goes out the antenna connector. 

In the reviews of Ramsey Q Amp in eHam.net, there is quite a bit of criticism of the product and a list of fixes to make it more reliable.  The circuit uses power MOSFETs  as the finals, probable IRF512s, and this appears to be where most of the problems come from. Power MOSFETs are notoriously unreliable when used in linear applications.  The negative threshold voltage coefficient causes thermal runaway and hot spotspots on the die. They also have VHF oscillations if the gates are high impedance. 

I cannot find a schematic online for the Ramsey Q Amp so I may have to reverse engineer a schematic for it.    I suspect the unit works so I look forware to testing it.