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Technical Tips from Mark W. Persons |
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Silicon Valley 700 Watt Amplifier Modification |
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August 25, 2017: This is a
Silicon Valley
model #0101-700CH FM RF Amplifier. It is capable of
delivering 700 watts of 88 to 108 MHz RF from just 10 or 20 watts of RF drive.
Continental 816 series FM transmitters use them as an IPA module to
drive the final tube. Powered by 48 VDC,
the modules fail heat and age after years of use. |
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Here is the circuit card after removal from inside the enclosure.
Heavy arcing on a bypass capacitor caused a fire and destruction of the
two transistor arrays. This one was not repairable. |
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This is the amplifier module with a new
Broadcast
Concepts BLF188XR 1000 Watt Planar Pallet Amplifier (Model
P1000FM-188PLA). The amplifier is capable of 1000 watts and will
tolerate up to a whopping 65:1 VSWR. Don't plan on running it at
1000 watts in a Continental FM transmitter because the transmitter's
power supply is not capable of enough current to do that. Normal
power output in that application is 300 to 400 watts. The pallet
amplifier will run comfortably 24 hours a day.
There is an RF attenuator on the
input to reduce 10 watts of exciter RF drive to about 3 watts. The
attenuator is a 150 ohm resistor to ground, then 50 ohms to the
amplifier input and 150 ohms to ground at that point. |
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| Here it is with a shorted quarter wave stub trap to protect the amplifier when there is an arc-over in the transmitter's tube. The stub is inexpensive and worth every penny. |
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The stories go on and on.
Stop in again sometime. I'll leave the soldering iron on for you.
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Questions? Email Mark Persons: teki@mwpersons.com |
