[Milsurplus] TV-2/BU tube checker problems...

[Kenneth G. Gordon]

I am not sure what is going on with my TV-2/BU tube checker, 
but it has been acting extremely strangely and I am not sure if 
this action is normal or not.

1) The last time I tried to check some 0B2 and 0A2 VR tubes 
with it, the VR tubes kept flashing and drawing more current 
than they should for a bit, even at the low current rating of 5 
mA. If I let them get good and hot, they would sometimes settle 
down. HOWEVER,

2) After checking several of them, BOTH 3 amp fuses blew.

3) After dismantling the tube-checker, I find that a) the 83 
mercury vapor rectifier exhibits signs of severe overload; large 
pieces of black material hanging from the top of the plates, and 
the filament open, and b) one of the 6X4 rectifiers has either 
gotton hot enough to crack the glass at the top of the bottle 
around the tip, or the tip was cracked to begin with and let all 
the vacuum out. ;-)

4) So, I replace the 83 and the bad 6X4 and proceed to check VR 
tubes. With MOST of the VR tubes, a lot of flashing occurs, with 
glowing gas appearing outside of the cylindrical plate against 
the glass and the tube getting hotter than heck; way too hot to 
touch.  SOME VR tubes, most notably GE made 0B2WAs, test 
properly and without incident.

5) Eventually, BOTH 3 amp fuses blow again, and when I open 
it up, replace the fuses and turn it on, the 6X4 I just replaced 
starts to arc over inside a few seconds after it starts to come up 
to temp, and blows ONE of the fuses.

6) I replace that 6X4 with a new one.

7) I attempt to test another 0A2, get the flashing, and decide to 
try to get some advice from someone with more experience 
along these lines.

8) One funny thing: many of the 0B2s which flash in the tester, 
act completely normally in a circuit where I am using a pair of 
them to regulate the screen voltage for an amplifier using a 
pair of 6146s.

9) I am toying with the idea of removing and testing the filter 
caps in the TV-2/BU, but haven't yet.

Are there any ideas from the collective wisdom?  What else is 
there to check?

Ken Gordon W7EKB