[Boatanchors] DRAKE TR-3

[Garey Barrell]

Paul -

Yes, that cap can cause several strange problems, such as random VOX 
operation, CW Sidetone 'leak-through', etc.

But how does VOX hang 'partially' closed??  :-)

Fried finals are typically caused by Bias supply failure, not VOX 
failure.  Failure of the Bias supply allows the VOX relay to close, 
which by itself is not a catastrophic problem, BUT that same loss of 
bias also allows the finals to draw max (a LOT with sweep tubes) current 
rather than normal 100 mA.  By the way, this can happen with the 
transceiver sitting in Receive mode.

Any AC-3 or AC-4 with the original Bias supply electrolytics in it is a 
disaster looking for a time to happen.  Usually when you're out of the room.

73, Garey - K4OAH
Glen Allen, VA

Drake 2-B, 4-B, C-Line&  TR-4/C Service Supplement CDs
<www.k4oah.com>


Paul Kraemer wrote:
> Don't overlook the de-coupling electrolytic filter cap in the mic pre-amp
> and vox circuit
> It will also cause the vox to hang partially closed
> Paul K0UYA
> ----- Original Message -----
> From: "David Stinson"<arc5 at ix.netcom.com>
> To:<boatanchors at mailman.qth.net>
> Sent: Sunday, November 22, 2009 3:37 PM
> Subject: Re: [Boatanchors] DRAKE TR-3
>
>
>    
>> Both the TR-3 and TR-4 have a "vox" tube,
>> 6EV7, I think... dual triode (forgive me, it's been
>> a lot of years).  It gets leaky and does all kinds of
>> wierd things.  The PTT relay winding is in the plate circuit
>> of one of them.  Could be just slightly pulling the relay.
>> If you let it go, the rig starts "hanging"
>> when you let go of the PTT.
>> Eventually it will start keying itself.
>> And if you still don't change it, you'll come home to
>> a shack full of smoke from fried finals.  Voice of
>> experiance.  A lot of TR-3/-4 PTT relays have been changed
>> when this tube was the real villian.  Get a new one,
>> even if yours checks "good."
>>
>> ----- Original Message -----
>> From: "AD5VJ Bob"<rtnmi at sbcglobal.net>
>> To:<boatanchors at mailman.qth.net>
>> Sent: Sunday, November 22, 2009 2:54 PM
>> Subject: [Boatanchors] DRAKE TR-3
>>
>>
>>      
>>> I am in the middle of restoring a Drake TR-3 and so far everything is
>>> going
>>> well.
>>>
>>> However, I have a question:
>>>
>>> I have her receiving a cw signal right now on 14.025 or so, but the
>>> speaker volume seems low and the S needle is sitting at 20 over
>>> nine in rx mode.
>>>
>>> I cleaned the tube sockets with WD-40 and the wafer switches, but it
>>> didn't change anything.
>>>
>>> I am guessing I may have an AGC tube starting to go south, but dont have
>>> a
>>> tube checker to be able to tell.
>>>
>>> I also have around a .05 reading steady reading on the plate current
>>> meter
>