[Amps] 4CX1600B - Bangs

[gdaught6 at stanford.edu]

KL7RA wrote:

> Interesting debate on the 4CX1600B tube. This is a real workhorse tube
> and it's too bad it has been dropped by the amp makers due supply
> problems. 

I agree.

> I never heard from anyone that had the tube "bang" and found it still
> good or bad unless I missed it from the postings. 

OK.  I've had a "bang" event in my HB '1600b amp, one time.  Afterwards, the tube 
was fine.  The only damaged component was the shunt resistor for the screen grid 
current meter, which exploded.  The meter movement was fine (back-to-front diodes 
across it, of course).  The amp has run reliably and uneventfully since (about 4 
years.) [Crossed fingers, salt-over-the-shoulder.]

Also, I had a "bang" in my 4cx800a MLA2500B conversion.  The exploded resistor(s) 
there were the "cathode degeneration" resistors from cathode to ground.  Whether 
they all went at once, or one at a time, I don't know.  I replaced them with a single 
Caddock high power resistor which was up to the task, and the amp has been OK 
ever since.  [Crossed toes, salt-over-the-other-shoulder.]  The tube is fine.

Summary:  two Russian tetrodes; two bangs;  exploding resistors in both cases (in 
different parts of the circuits); tubes fine in both cases.  Root causes of bang events 
unknown.  I can't ascribe them to parasites, DC voltage surges, cosmic rays, or 
whatever.  

WHAT IS VERY NICE IS THAT THE TUBES ARE FINE.

As always, YMMV.

73,

  George T. Daughters, K6GT