Do the Triac mod so you have a resistive 120 ma contact load and the switch will outlast you and no more arcing. Don't forget to remove the RC filter across the switch contacts.
The Triac doesn't need it, the Littlefuse Alternistor series I mentioned is designed for high inductive loads and no filter needed. A Triac switches off as the sine wave goes through zero so there is no arc to be suppressed.
It is a surplus part as long as you use an Alternistor series.
No I have no ties with Littlefuse. I just stumbled on a good thing.
My LR-9090 is still cranking fine and I tend to turn it off and on every time I go past my test bench to continue looking for a failure even though I do not expect one.
Does your switch have 1 or 2 contacts and if 2 are they both used?
I need to download the SM for your SX and look at the ckt.
Sorry to drag this up. yes a triac opens when the current goes through the zero crossing. However the voltage and current aren't likely to be in phase. Therefore it is possible that the triac would open with a high voltage across it.
That is an internet myth. It has been repeated so often it has taken on an aire of authenticity. Best guess was a bored EE student for a laugh. Sounds like something I or a roommate might have done.
A transformer reflects the load (secondary) impedance to the input (primary). If the secondary load is resistive, then the load as viewed at the input is resistive / in phase.
Amplifier power transformer secondary's are wired to rectifiers. That is DC i.e. resistive. A tiny secondary AC load may be incandescent pilot lights also resistive / no phase shift. Some of the newer units have switching power supplies, but the ones I have looked at start with a rectifier to a DC buss then to the switcher so still DC / resistive as viewed from the input.
Think about it. If that were not the case the power grid would never work. The substation transformers would add so much phase shift any AC motor would burn up from over current, your light bulbs would barely glow. At 90 degrees there is no real power available.
We got to do the calcs to determine the transformer addition to and effect on the secondary as seen from the primary in first or second year EE. The component of load viewed from the primary added by the transformer had best be negligible or the transformer is trash.
Questioning everything is a good. The older we get the less we question what we were taught and learned over the years. That is why most discoveries and inventions are done by newbies that didn't know it couldn't be done.
In the time you took to impressed us with your EE degree you could have proven your alleged myth by capturing the input current and voltage on a scope to show they were in phase. You might also capture the peak current at turn on, with power supply caps completely discharged so you would know if you exceed the I2T rating of the device. that would tell you if the triac could survive in larger amplifiers with large capacitance.