SWR Strawberry Blonde popping noise turn on /turn off

[nosaj]

I have a strawberry Blonde that makes a popping noise when turning/ on or off. I see that on the web it says that this is normal however the customer says it it now more pronounced. I have 2 questions

1 How do I determine which revision i have to find out what schematic I need?
2 The popping noise is it related to the power switch or the power supply and what might one be able to do about it?

Thank,
nosaj

[Jon Snell]

Sounds like a mains issue.
I would fit a 4n7 class Y capacitor across each mains switch contact and a 100n class X across the mains before the switch, to act as a snubber and stop any interference.

[nosaj]

How could i implement your suggestion with a SPST switch?

Thanks,
nosaj

[nosaj]

Nevermind I got it. 100 nf across IEC connector and a 4.7 across switch. Noise gone. Thanks a bunch Jon

nosaj

[nosaj]

Hi Jon, how did you come up with those values?

Thanks,
nosaj

[Jon Snell]

They are the values I have used, over the years.
100n class X sits across the mains to filter out most of the mains borne interference and mains spikes, caused by the on/off switch.
The 4n7 class Y is to dampen the HF from the contact bouncing when switching in either direction.
Of course, a single pole switch, only requires one 4n7.

Pleased to help.
Jon