Garey Barrell <[EMAIL PROTECTED]> made an utterance to the drakelist gang
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Is the tone oscillator working?
The "flash of bias" may indicate that the oscillator is NOT running.
You hear the relay click in, but does it STAY in? There is a "speed-up"
circuit that puts a pulse of current to the relay to pull it in fast so
as not to lose the first "dit" or syllable of voice. After that pulse,
the tone oscillator (mic amp with phase shift network) should hold the
relay closed. The mic amp tube may be weak and fail to start at some
times, or the high value resistors in the phase shift network may have
gone up in value.
I've never found a bad MODE switch that hadn't been damaged by someone
trying to "clean it" with Q-Tips or other mechanical tool. Black silver
sulfide does NOT inhibit operation of a silver plated switch. Fixed
contacts ARE susceptible to being "sprung" or otherwise damaged. The
T-R relay contacts are far more likely to be the problem than the mode
switch contacts.
If the oscillator IS running, then there may be a problem later in the
VOX circuit. The VOX is held in by rectifying the tone and charging a
film capacitor, so there are several ways for it to get "lost" before it
keys the 6EV7 VOX relay tube.
73, Garey - K4OAH
St Charles, IL
Drake 2-B, 4-B & C-Line Service Supplement CDs
<www.k4oah.com>
[EMAIL PROTECTED] wrote:
Hello to the group,
Looking for ideas before I really start to tear things apart.
The subject say's it all....TR4 will not load........now most of the
time. I have brought this up before .When it does load its between
150 & 180 Watts to the dummy load as per a W4. .
Now you'd have to know that with another very recognized list member
it behaved like a baby, although it needed an alignment, particularly
on 20 M.
Bias has been checked, numerous times, at resistor R 45. Been through
the relay (cleaning etc) three times now.
Mode switch in SSB, activate the mic key and the relay clicks and I
can get bias., no additional can be cranked in.
Normal bias procedure Sideband switch to non X and then the mode
switch to X-CW This should give bias, sometimes does sometimes
doesn't. Past tense, most of the time it did. But now in all cases
when the switch is returned back to SSB position it flash's
bias...indicating a bad mode switch....been through it cleaned it as
much as possible etc. Am about ready to remove all the surround and
unsolder it to get a better shot.
Now for a normal tune up procedure, sideband switch in X and then mode
to X-CW to load ...NADA !
This event has occurred literally every time for the last several days
of working with.
But it did load up ...once....this evening. Tonight I did notice that
the cage was fairly hot, as was the Cinch-Jones connecter indicating
to me rather heavy current flow...
Suggestions?
Carl WD8NHK
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