"Don and Diana Cunningham" <[EMAIL PROTECTED]> made an utterance to the
drakelist gang
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Rob,
Mr. Simpleton here, I must confess, but it was always MUCH easier for me to
set bias with the Drake gear, assuming that the meter worked, (Garey's post
covers that though) by using either a microphone in the SSB mode and pushing
PTT with no audio or keying the rig up with a clip lead in the SSB mode.
That's the only way I learned to do it (again, other than getting inside
like Garey suggests). I haven't seen that suggested. Like I say, probably
too simple but always worked for me.
73,
Don, WB5HAK
----- Original Message -----
From: "R. Ton" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>; "Drakelist" <drakelist@www.zerobeat.net>
Sent: Sunday, April 16, 2006 10:38 AM
Subject: RE: [drakelist] TR-4C transmitter troubleshooting
"R. Ton" <[EMAIL PROTECTED]> made an utterance to the drakelist gang
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Thanks to all (!!) -- more coming when I get a chance (life is getting in
the way of fun right now).
So far, I've had the chance to change out the relay -- the ONE spare part
I had on hand. No difference. The rig does go into transmit when
switched
to CW mode (no key plugged in). Both relays respond and the receiver
mutes.
I just noticed this AM that the .025 plate current reading I get is there
even with the power off. Meter moves about a needle's width when put into
transmit and the S-meter reads about 7-8 in transmit -- may be another
clue?
And thanks for the hollow-state theory Garey. It's been a REALLY long
time
since I've worked on any tube gear, but it's slowly coming back to me. :)
I'll be digging some more in a bit here and will report back. I'll also
see if I can catch the technical net this afternoon. 7.238 @ 2000Z,
right?
Thanks again everyone!
73, Rob (KFØRT)
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] Behalf Of Garey Barrell
Sent: Sunday, April 16, 2006 8:41 AM
To: Drakelist
Subject: Re: [drakelist] TR-4C transmitter troubleshooting
Garey Barrell <[EMAIL PROTECTED]> made an utterance to the
drakelist gang
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Hi Kevin -
Expertise is just experience clouded by memory! :-)
I don't think I've ever come across a PAIR of finals that "lit up", but
wouldn't draw at least a couple hundred mA if they had the DC potentials
applied to them. In fact, I can only remember one tube that was "open",
but lit. I still think it had a broken weld inside it!! :-)
But then I've been wrong before. A favorite med school phrase, "when
you hear hoof beats, think horses, not zebras" comes to mind!
Hopefully Rob will get it fixed in spite of my help and let us know the
truth!!
73, Garey - K4OAH
Atlanta
Drake B & C-Line Service CDs
<http://www.k4oah.com>
kbgluxford wrote:
>
> kbgluxford <[EMAIL PROTECTED]> made an utterance to the drakelist
> gang
> ----------------------------------------------------------------------
> I certainly don't have Garey's expertise or long experience, but I did
> have a similar problem on one of my TX4 transmitters recently. I
> changed out the PA tubes and the problem disappeared.
>
> 73
> Kevin
> VK3DAP / ZL2DAP
>
> Garey Barrell wrote:
>>
>> Garey Barrell <[EMAIL PROTECTED]> made an utterance to the
>> drakelist gang
>> ----------------------------------------------------------------------
>> Rob -
>>
>> You don't mention anything about "keying" the transmitter. You have
>> to "key" the Push-To-Talk (PTT) of the microphone to switch it to
>> transmit to see the idling plate current. You should hear the relay
>> click when it closes.
>>
>> If the final tubes have plate voltage, screen voltage and filament
>> voltage, and the cathodes are returned to the negative pole of those
>> supplies, they WILL draw plate current! The grid voltage is the
>> only thing that keeps them from drawing AMPS of current in the
>> presence of the other voltages.
>>
>> There are two RF chokes in series between the +650VDC supply and the
>> plate caps of the tubes. There is a 15 ohm, 1W resistor in series
>> with each of the final tube cathodes to another RF choke, through the
>> meter shunt resistor, and then through a relay contact to ground.
>>
>> 73, Garey - K4OAH
>> Atlanta
>>
>> Drake B & C-Line Service CDs
>> <http://www.k4oah.com>
>>
>>
>>
>> R. Ton wrote:
>>> "R. Ton" <[EMAIL PROTECTED]> made an utterance to the drakelist gang
>>> ----------------------------------------------------------------------
>>> I'm finally digging into a TR-4C I bought used some time ago. It
>>> "worked
>>> fine" when it was shipped here, but I haven't been able to get any
>>> power out
>>> of the transmitter. It at least oscillates -- I can hear it on a
>>> receiver
>>> in the same room.
>>>
>>> Starting at the beginning...
>>>
>>> The manual says to adjust the bias on the AC-4 so that the plate
>>> meter reads
>>> .1 amp. This is with the sideband switch counter-clockwise and the
>>> xmtr
>>> gain all the way down. The meter seems to read about .025 in
>>> receive and
>>> goes up just a little when the rig is switched to CW. Adjusting the
>>> bias
>>> has no effect on the plate meter, but it does indeed adjust the bias
>>> voltage. Setting it to -60 volts is no problem, but I'm unable to
>>> get any
>>> "real" plate current no matter what I do. Any ideas?
>>>
>>> I haven't done anything to the radio since I got it except spray the
>>> switches with Deoxit D5 and replace R45 (2 ohms -- plate meter shunt
>>> resistor!!). This resistor was fried in half.
>>>
>>> What am I in for?
>>>
>>> Many thanks in advance!
>>>
>>> 73, Rob (KFØRT)
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