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[TenTec] Century 22 fault stil not solved

To: <tentec@contesting.com>
Subject: [TenTec] Century 22 fault stil not solved
From: K5BDZ@aol.com (K5BDZ@aol.com)
Date: Fri, 17 Nov 2000 20:03:09 EST
Bill
I apologize for not contacting TenTec for you this week.  I was called out of 
town and just returned.  However I've been analyzing the Century 22 problem 
(and recalling the schematic from memory) and let's try this:
The problem at high power and not low power indicates that probably your 
keying circuit is OK.  Let's check the driver circuit (my first choice) and 
the final amp circuit (2nd choice).
It appears that the circuit in question (start with driver) is not getting 
enough current, and working only off a charged electrolytic capacitor until 
drained (high power, quickly drained, low power slower drain and barely 
sufficient current to maintain operation), then the limited power into the 
circuit is pulsating on hi power trying to properly supply the circuit.  I 
would follow the 12 volt line thru the driver circuit, testing voltage on 
key-down on driver collectors.  It could be a bad series resistor, bad solder 
joint, or bad connector.  Transistors, unlike tubes, are usually not prone to 
get soft and "die away" on key down.
Voltage checks (with RF probe) should be done on driver bases.  If all fails 
to show problems on the driver circuit, then do the same on the final amp 
circuit.

FINALLY, I do not remember if the driver circuit has a trim-pot to adjust the 
pre-driver drive to the driver.  If so, that's my first item to clean and 
insure operation.

Keep us posted on your findings.
Thanks
Bill, K5BDZ

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