Half power switch

[PhilUK]

Seen this mentioned a few times, do we know if it was a factory mod or available to order?
I've seen a hole pre-cut in an early 74 chassis (presumably for the switch) which was then covered by the serial plate.
Any body else seen this?

PASwitchHole.jpg (323.68 KiB) Viewed 1257 times

[PhilUK]

Sorry forgot to ask exactly how the half power was achieved. What did the switch do?

[Dr.HI-TONE]

the hole was present till the mid 1970's
when activated the switch lowered via a large resistor, the voltage on the plates

[PhilUK]

Thanks for that, was this an option available when ordered or was it a special or even a later factory mod do we know?

[Dr.HI-TONE]

It was an option for new products early on. I think it was phased out as it is very hard on the tubes unless you place the amp on standby before switching.
I would have to guess that it simply wasn't worth the trouble that came with users flipping the switch repeatedly without using the standby switch.
But that is just my theory.