[Boatanchors] Heathkit TT-1 filament current regulator capacitor

[Jim Wiley]

Charles -


To set "in-between" voltages on a TT-1 tube tester,  plug a VOM (on the 
AC Volts range) intro the filament pins of an unused tube socket, and 
adjust the "line adjust" control until the correct voltage is 
indicated.  As long as you don't get too far off the center-scale "line 
voltage set" indication, you should be OK.  

For example, when testing  2A3  tubes, the TT-1 can't really supply 
enough current to heat the tube properly at the 2.5 volt setting (the 
resulting voltage at the socket is  much too low), so I use the next 
highest setting, which is 3.3 volts, and use the line adjust to set the 
heater at exactly 2.5 volts.   Since all sockets will receive filament 
voltage,  you can take any unused socket and make the measurement.   
While the line adjust control does affect the other voltages in the 
TT-1, as long as you are not too far off base, you should be OK. 


The way the switches work to deliver power to the tube socket pins,  
briefly, is like this:  The filiament voltages come from whichever 
socket pins are set to "6" and "7" on the selector switch bank.  Each 
selector switch corresponds to a tube socket pin.   Switch # 1 goes to 
all socket #1 pins,  switch #2 goes to all socket #2 pins, etc.    The 
switch positions around the circle determine what is connected.   
Position 3 is plate voltage, position 4 is screen, position 5 is grid, 
etc. 


When testing tubes with a high current draw, limit the time the tube is 
drawing power.   You wouldn't want to fry the transformer or burn up an 
interconnecting wire.    The "13" position is the correct one to use for 
12 or 12.6  volt tubes.  The instruction manual, as well as the 
roll-chart will tell you what filament voltage to use.   In the case of 
the "current limited" tubes, they will test equally well using the 
"rated" voltage as  using the "current limited" voltages.  The latter 
are primarily there, as I understand it,  to make sure the tube will 
warm up in an acceptable time for series string use - which is to say 
not too soon or too late. . 


- Jim, KL7CC






Charles Johnson wrote:
> Has anyone found a suitable replacement for C9, C10 and C11 in the 
> TT-1? This is the large 3 section oil filled AC capacitor that is used 
> as a current regulator for the 300, 450 and 600 ma filament current 
> positions. This cap has two 3.6 and one 7.1 ufd sections and they are 
> high by about 10% which raises the allowable filament current and thus 
> the voltage to the tube under test, giving false test readings. Using 
> other filament voltage positions is a work around in some cases, but 
> the TT-1 doesn't have a 12.6 volt filament position, for instance.
> Any ideas appreciated.
> 73, Charles, K4ZRJ
> _______________________________________________
>
>