# Mod: Fender 68 CDR RI (resistor on stand-by switch)



## _Knighthawk_ (Mar 2, 2014)

All,

Has anyone ever tried to resolve the stand-by switch 'pop' issue by installing a (47k 2W) resistor over the switch. I recently read about this mod for a 5E3 build and wondered if anyone had ever tried it on a newer Fender amp.

My 68 CDR (RI) has an annoying 'pop' when I use the stand-by switch. I have read that this is common and while that may be true, it is nonetheless very annoying. I had thought about giving this little mod a try to see if I can get rid of that popping sound on the stand-by switch.

Any thoughts/feedback are appreciated.

Cheers.


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## zurn (Oct 21, 2009)

I have the same issue with mine, I never use the standby switch


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## _Knighthawk_ (Mar 2, 2014)

zurn said:


> I have the same issue with mine, I never use the standby switch


Me either. 

But I'd like to...


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## GTmaker (Apr 24, 2006)

Would turning the volume down to zero before engaging the stand by switch solve the popping sound?
I think it would but I cant test it to be sure.

G.


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## greco (Jul 15, 2007)

@_Knighthawk_ Last evening, I was reading this in the EXCELLENT link(s) that you provided. Many thanks for those!

Will you need to add a cap in parallel with the resistor?:

*Standby Switch 'Pop Reduction' and Current Surge Protection*

One modification I highly recommend is a resistor across the Standby Switch terminals. It will quiet or eliminate the Standby Switch 'pop' by allowing a small current to flow around the Standby Switch to charge the Filter Capacitors. This prevents a current surge when you close the Standby Switch.

You should always ensure the Standby Switch is in the standby position before powering up the amp. Turn on the Power Switch then wait around 15 seconds for the tube heaters to come up to temp and for the pop resistor to charge the filter caps enough to prevent a current inrush which is what causes the pop. Preventing the current inrush will also make your filter caps last longer.

The Valve Wizard recommends a resistor between 47k (2watt) or 150k (1watt). I had a 100k 2watt on hand so I used that. Adding the resistor eliminated all pop for my amp *but you may need to install a 0.047uF 1000volt capacitor across the Standby Switch terminals (in parallel with the above resistor if you choose to install both).*










_Pop Resistor (grey 100k 2 watt) across the Standby Switch_


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## _Knighthawk_ (Mar 2, 2014)

That's exactly where I read about the mod. Not sure if the cap is necessary or not. I had thought I would try the 48k2w first and then get a cap if needed 

I was hoping someone had already tried this. I guess I'll be the guinea pig!


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## _Knighthawk_ (Mar 2, 2014)

48K2W not enough to make pop go away. Will try adding cap (in paralell) when next I am motivated.


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## copperhead (May 24, 2006)

If it has a Rectofryer tube ...hehe .Standby switch is not so important as if the amp without a rectifier . the Rectifer tube adds a cushion causing the voltage to come up slower .
But i am interested in this fix to cure the pop in my '68 CDR as well


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