[Drake] T-4XB--no output

[Garey Barrell]

Al -

It's a 680 ohm.  This is one of several resistors that are often killed 
or seriously wounded by people using uninsulated screwdrivers for 
alignment.  Shorting the top plate of the trimmers to the chassis (easy 
to do with those little holes) puts the full 250V supply to ground 
through that poor little resistor.

It's located right up against the shield next to the 12BY7, on the PA 
side.  Right out in the open!

A voltage check may not find it, if it's just gone up in value, since 
the voltage charts are made in standby.

73, Garey - K4OAH
Atlanta

Al Parker wrote:

>Hi Paul,
>    Just another suggestion to add to the list, from someone who's been
>there:
>    Take a look at the resistor feeding the driver plate, I think it's abt
>470 ohms, mounted on the final side of a chassis wall from a feedthru, if
>my poor memory serves.  After it happened to me I thought, "gee, that's a
>good way to run QRP."  It's half watt, guess it can run hot & go high or
>open up.
>73,
>Al, W8UT
>New Bern, NC
>BoatAnchors appreciated here
>http://www.thecompendium.net/radio/
>http://www.hammarlund.info
>
>----- Original Message ----- 
>From: "Paul Ellis" <homepaul at raccoon.com>
>To: <drake at mailman.qth.net>
>Sent: Sunday, October 10, 2004 11:53 PM
>Subject: [Drake] T-4XB--no output
>
>
>  
>
>>Hi, all--
>>
>>Thanks again to all who helped me troubleshoot my R-4B a few weeks
>>back.  Once I got that buttoned together, I started turning my attention
>>    
>>
>to
>  
>
>>my T-4XB, which isn't working right.   The problem is that there's no
>>output from the transmitter on the wattmeter.
>>
>>I first suspected a bad driver tube and/or finals, so all three tubes
>>    
>>
>had
>  
>
>>known good tubes substituted.  Voltages check out from both the power
>>supply (bias is correctly set at -62V) and the filament fuse is just
>>    
>>
>fine.
>  
>
>>Voltages seem to check out at each of the pins of  V4, V5 and V6, too.
>>
>>With the R-4, I can detect a very low level of drive out. Adjusting the
>>plate, preselector and load and drive does make a difference--I can hear
>>    
>>
>a
>  
>
>>weak signal on the receiver, complete with audio, etc., and it's
>>    
>>
>peakable
>  
>
>>using the transmitter controls.  I'm suspicious of components near and
>>around the driver circuit, but need more ideas on where to look and what
>>    
>>
>to
>  
>
>>look for.
>>
>>As always, I appreciate all the thoughtful responses I get from all of
>>you.  Thanks in advance!
>>
>>73,
>>Paul
>>KA0JQF
>>    
>>