[TenTec] Titan 425 troubles, R1 and blown 20a fuses

[Dr. Gerald N. Johnson]

On Sat, 2007-07-21 at 19:56 -0300, VE1BN wrote:
> Jerry -
> 
> Would it be conceivable that the problem is AFTER the wirewound resistor, 
> and not the caps or the transformer?

Don't know. I don't know the circuit details.

Back years ago before the diode makers learned to make controlled
breakdown diodes we put capacitors and resistors across the diodes
supposedly to equalize the reverse voltage. Of course the resistors made
the diode assembly have a lot more reverse current that the diodes
alone. That put some AC on the filter capacitors. As did the capacitors.
Worse, most diodes had a higher voltage breakdown than carbon comp
resistors and sometimes the capacitors, and using 20% resistors with GMV
ceramic capacitors had to make the back voltage distribution poorer than
the diodes alone. Add in some ceramic capacitors that change value with
applied voltage and that "even" voltage distribution probably killed
more diodes than leaving them alone. Then along came diodes with
controlled breakdown and the diodes and capacitors became old history.
The .01 caps probably protected the diodes from transients, and a single
high voltage capacitor on the transformer secondary may have been as
effective without adding to the power supply ripple.

> I had a Titan some years ago.  A 
> rectifier broke down so I replaced them all with new ones plus I added .01 
> caps across each.  Never a problem thereafter.  I would suspect the problem 
> the gent has is after that wirewound resistor.
> 
> 73 -  Don,  ve1bn at eastlink.ca 
-- 
73, Jerry, K0CQ,
All content copyright Dr. Gerald N. Johnson, electrical engineer