[AMPS] good, bad, ugly

[km1h@juno.com (km1h@juno.com)]

My experience with the big Ameritron amplifiers, from strictly a service
viewpoint, is that  tube generated heat is generally not a problem. Those
amps use a decent blower and exhausting is not great, but adequate.  For
those that insist on running at or close to the 1500W level on RTTY I
would suggest  modifying the cover for better air egress. Adding a
silicone rubber plenum tube from the anode to the top of the cover would
be the final step in the modification. 
Silicone rubber sheet  with a 500 degree F rating is available thru
McMaster-Carr. Their part  # for a 12" x 12" piece is 8632K43, specify a
durometer hardness of 50 when ordering.  

Both the AL-1200 and 1500 are rated in the manuals at 1500 W PEP output
at a 100% duty cycle. What that translates to for various modes of
operation I am not sure. 

What does appear to be a problem is the Pi-network components and
mounting methods. RF heating of coils and solder joints is evident in
many of the amps I have serviced and appear to be related to 80 and 160M
operation. Whether the fault is inadequately sized components or the PI-L
design used on the those bands I cannot say.  I do suspect that RF
heating and capacitance drift of the various fixed capacitors that are
used on those bands plays a part. 

In all fairness to Ameritron I must also agree that their service
department has always been excellent in getting parts shipped. 

For the price you get a good product; if you need a great product buy one
of those Creative Labs 3CX3000 amps.

73...Carl   KM1H

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