On 06/04/2011 10:07 PM, raypsi wrote:

hey OM

The dead give away should have been the series resistor to that OA3
heating up big time since P=I^2R the current doubled, the power
quadrupled that resistor would have could have let its' smoke out.

73 OT
de n8zu
Unless the original designer was paranoid enough to use an over sized
resistor in the first place. Back when I first started out in ham radio
building with tubes I was guilty of using a 50W resistor in a 5-10 watt
circuit. (half because I got the 50W part cheap and half because I knew
that I didn't quite know what I was doing and wanted to be safe).

On Jun 5, 12:16*pm, Kenneth Scharf wrote:
On 06/04/2011 10:07 PM, raypsi wrote:

hey OM

The dead give away should have been *the series resistor to that OA3
heating up big time since P=I^2R the current doubled, the power
quadrupled that resistor would have could have let its' smoke *out.

73 OT
de n8zu

Unless the original designer was paranoid enough to use an over sized
resistor in the first place. *Back when I first started out in ham radio
building with tubes I was guilty of using a 50W resistor in a 5-10 watt
circuit. *(half because I got the 50W part cheap and half because I knew
that I didn't quite know what I was doing and wanted to be safe).

In my case problem was only momentary, maybe a second sometimes going
days without doing it sometimes 3 or 4 times in a couple of minutes.
For a long time I was convinced it was in the amp instead of the power
supply because I once disconnected the power supply from the amp and
it ran continuously for a few weeks without failing. This turned out
to be just bad luck. Fortunately I am on the air about as sporadically
as the amp was failing. There is no telling how many times it failed
while I was using it and I just didn't notice.


Jimmie