Garey Barrell <[EMAIL PROTECTED]> made an utterance to the drakelist gang
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Bill -
The definitive article on the PA brick itself is at
<http://www.wb4hfn.com/DRAKE/DrakeArticles/TR7_Amp_Repair/TR7-Amp.htm>
A first check is at the input to the PreDriver board. You should see ~
1 v p-p here on the low bands, dropping to ~0.5V p-p on 10M. If levels
here are good, the problem is in the brick itself. If these levels are
low, it's possible that one or more of the PIN diodes used to switch the
INPUT to the PA and/or the PIN diodes used to switch the calibrator
signal off and on is shorted or open.
<http://www.wb4hfn.com/DRAKE/DrakeArticles/PinDiodeTest.htm>
is for the RF switching diodes.
The calibrator diodes are CR1401 and 1402, and can be checked
in-circuit. Typical failure is shorted CR1402. IF it is shorted, it
can be removed entirely until a replacement can be gotten. The
calibrator signal will be weaker, but not a problem.
The slightly lower output on 160 is normal, and is a result of the
output bandpass filter rolling off.
73, Garey - K4OAH
Atlanta
Drake 2-B, 4-B & C-Line Service Supplement CDs
<www.k4oah.com>
Bill Carpenter wrote:
"Bill Carpenter" <[EMAIL PROTECTED]> made an utterance to the drakelist gang
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My TR7 has experienced a lessening of output power on the higher bands
by quite a bit and 160 meters is also a bit low:
160 110W
80 120
40 120
30 120
20 114
17 80
15 71
12 60
10 65
Measured into a good 50 ohm load with a Daiwa meter that is accurate.
Any help is appreciated!!
763,
Bill NZ0T
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