[Drake] Re-cap on TR-4

[Garey Barrell]

Mel -

I would NOT replace all tubes.   This is "sometimes" ok if you have a 
set of KNOWN GOOD tubes, but usually just confuses the issue.  If you're 
not prepared to go through with a meter to find the specific bad tube, 
IF it even IS a bad tube, you could replace them one at a time.  Replace 
one, turn on tx and see if it still has the problem.  If not return the 
original tube and try the next one.  Much better to measure the filament 
voltage across each tube.  Make a chart, and be sure to check each one.  
Also examine D/B switch and wiring on the rear panel.  This switch 
selects Bright or Dim panel lights by inserting a resistor in series 
with the bulbs.

The 10M segment problem is probably a bad crystal.  Some TR-4's did not 
come with all three ten meter segment crystals installed, and someone 
may have just added two crystals.  If all three are there, try swapping 
the one that doesn't work with another ten meter one.  It won't be 
peaked, but you should be able to tell if it's working or not.

73, Garey - K4OAH
Atlanta

Drake C-Line Service Manual
<http://hr99.home.mindspring.com/R-4C_Servicez/>



Mel Vance wrote:

>>Most likely a short on the filament line somewhere.  Look at the
>>schematic (verify it matches your serial number) and examine the
>>series / parallel filament wiring that includes the dial lamps.  It's
>>possible that it is a heater-cathode short in a tube, shorting the
>>filament string to ground at that point.  Bottom line is something is
>>shorting out a portion of the string, increasing the voltage on the
>>rest in that string.  Measuring the filament voltage across each tube
>>"may" help.
>>
>>1.  Any electrolytic is suspect.  Lacking an ESR meter, just replace
>>them.   Watch polarity!
>>
>>2.  The can is not for shielding, underchassis caps are fine.
>>
>>3.  It's a start!  :-)
>>
>>    
>>
>OK.....re-cap is a very good idea......
>
>To make sure, I can replace all tubes except driver and finals with out doing a bunch of re-
>tuning, right? Think I have all tubes except finals in the tube case...should fix any bad 
>filaments, and with a re-cap and touching up the tube sockets *should* fix the major 
>problem...
>
>Now, any ideas on the dead 10mtr segment...Dirty segment switch? Bad xtl? Any other 
>common causes?
>
>Mel
>N7OKL
>
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