On 07/31/2014 05:52 PM, Phil Allison wrote:
"Cydrome Leader"

BTW:

I could have added a RC network ( ie a Zobel ) across the 1 ohm wirewound
to
bring it line at 3MHz and well beyond. A 47nF cap and any 1 ohm, 0.5W
film
type would do fine.

Same goes for the 100W 8 ohm power resistor, a Zobel using 68nF and 8.2
ohms
corrects it to beyond 5MHz if that was ever needed.

I wonder how much that would confuse the next repair tech?

Bizarro repairs are always fascinating to come across.

** I have sometimes added a Zobel ( ie 22nF and 56ohms, 0.5W) ) across the
output of an amplifier that did not need it.

Why ? As a tell tale in case of supersonic oscillation.

Incorrect installation and bad cabling practices can cause almost any power
amp to break into oscillation at an inaudible frequency resulting in rapid
overheating and failure of output transistors etc

It's nice for a repairer to have proof when this has happened.


.... Phil



I listen to distant AM radio in the shop. An amp that breaks into
oscillation (often caused by "replacement" actives with way too much
bandwidth, BTW) will cause interference on the AM (MW) radio. It is as
reliable an indicator of oscillation as fat blurry traces on the Oscope.
Also, the amp pulls more current than it should when it breaks into
oscillating. Now a SMPS without EMI suppression already makes the
interference so all bets are off.