Garey Barrell <[EMAIL PROTECTED]> made an utterance to the drakelist gang
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Nick -
First step is to check the BIAS supply voltage. Easiest place to check
is on the feedthrough on the underchassis final amplifier shield. The
BIAS feedthrough is the second one from the front end of the shield.
It should measure, referenced to the transmitter chassis, from
approximately -45 to -65 VDC as the BIAS control on the AC-4 power
supply is varied.
These feedthroughs are, from front to back:
12 VAC
-55 VDC
+250 VDC
Cathode
+650 VDC
IF +650VDC is applied to the plates, ~250VDC to the screens, ~ -60VDC is
applied to the grids and the cathode is grounded, the final tubes WILL
draw ~100 mA of cathode current, _regardless_ of any other
conditions. Varying the grid voltage from ~ -70 to 0 will vary the
cathode current from 0 to 0.500 A.
If you are measuring voltages in this range and there is no cathode
current shown, the cathode is not being returned to ground. The
cathodes are grounded directly by the TRANSCEIVE switch in the RCVR and
XMTR positions, and by the T-R relay via the TRANSCEIVE switch in the
SEPARATE position. The Cathode terminal should read 0 volts with the
relay closed.
73, Garey - K4OAH
Atlanta
Drake C-Line Service Manual
<http://www.k4oah.com>
[EMAIL PROTECTED] wrote:
Gentlemen:
Original purchase transmitter.
My transmitter worked after for alittle while after pulling it from
storage for 3 years, and then the following began to happen............
My Transmitter displays the following symptoms:
1.) Very little idle current, and will not adjust over any appreciable
range.
2.)No plate current under any modes of tune up on any band.
3.)No sidetone, maybe once in a great while, but no plate current.
4.)All DC voltages are present at the tubes of the finals and
driver.Static.
Checked these voltages under keyed conditions , and they remained
fairly constant.
No sidetone.
5.)Finals, driver, and microphone amplifier tubes were replaced.
6.) VOX circuits seem to function, and transmitter VFO will work great
with R4C.BUT STILL THE ABOVE.
Thanks for the help in advance. Hope this is getting to you and Hope
to see you on the air.
73's
Nick Kiseloff
WA6GPW
Dallas, Texas
[EMAIL PROTECTED] <mailto:[EMAIL PROTECTED]>
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