Jim Lesurf wrote:


http://www.audiomisc.co.uk/Armstrong...nale/1982.html

I'm now curious that no-one has commented on the contents - particularly of
the 1982 page!


** You mention speaking with Peter Walker about the "crow bar" circuit in the ESL63. Here is a schem for an early version.

http://www.quadesl.com/schematics/quad63_schematic.gif

The triac used is a T6000B, rated at 16 amps continuous and 150 amp surge for 10mS. Other units use a T2800B, rated at 8 amps with a 100 amp surge rating.

Later ESL63s, from 1989 onwards, used a TIC216D, rated at 6 amps with a 50 amp surge rating.

http://www.euronet.nl/users/temagm/a...ematic_new.jpg

As the crow bar is intended to clip transients that exceed the voltage limit of the panels and only to be used with amplifiers that have electronic current limiting, any of the above are more than adequate.

Large amplifiers with no current limiting are warned against, but if used could fry the smaller triacs or the 1.5 ohm 5W resistor in series. Later models also had a circuit breaker in series.

In any case, the speaker itself was protected, because triacs invariably fail short.


..... Phil