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Post subject: Standby Switch Question
Posted: Tue Jun 03, 2014 6:31 pm
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Last week, I picked up a used Hot Rod Deluxe at a nice price. The amp works great, but I noticed a (perhaps) unusual quirk when turning the amp off.

When flipping on the Standby switch (which I usually do before shutting the amp off completely), it seems to take several seconds for standby mode to fully kick in. I still get sound from the amp or a 'crackle' from pulling out the guitar cable plug for about 10-20 seconds before the sound gradually, totally fades out.

With my last amp, I seem to remember the amp sound 'muting' almost immediately after flipping the standby switch and I'm wondering if my new amp is behaving oddly. I realize that standby mode is used for preheating the tubes when powering up and isn't really designed to be used as a mute. But I want to make sure this quirk is not indicative of a larger problem.


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Post subject: Re: Standby Switch Question
Posted: Wed Jun 04, 2014 1:08 am
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Your switch need to be cleaned ( or replace IMO ) , spray good contact cleaner with lubricant where is the "bat ".

Flip switch 10 times ( Amp Power OFF and disconnect )


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Post subject: Re: Standby Switch Question
Posted: Wed Jun 04, 2014 2:04 pm
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schnepf13 wrote:
...When flipping on the Standby switch (which I usually do before shutting the amp off completely), it seems to take several seconds for standby mode to fully kick in....


Totally normal. The DC voltage from the power supply caps are slowly discharging through the tubes, and the time that it takes to discharge is dependent on the type of tubes, bias level, and other factors. If you actually timed it, I'm sure that it doesn't really take 30 seconds.

I am not a fan of spraying anything into a switch, because mainly all that does is clean the lubricant from the switch. When the switch is put into standby, it is open, and cleaning it will not do anything for an open circuit, and it will not make the switch open any faster.

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---> "The amp should be SWITCHED OFF AND UNPLUGGED before you do this!" <---

Por favor, disculpe mi español, no se llega a la práctica con mucha frecuencia.


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Post subject: Re: Standby Switch Question
Posted: Wed Jun 04, 2014 2:17 pm
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Thanks, guys, for the information! Shimmilou, the research I found online last night seems to confirm what you said about the power supply caps discharging. It's quite probable that my previous amp did the same thing and I simply didn't notice before. Glad to know nothing is on the verge of breaking or blowing up!


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Post subject: Re: Standby Switch Question
Posted: Wed Jun 04, 2014 2:42 pm
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shimmilou wrote:
schnepf13 wrote:

I am not a fan of spraying anything into a switch, because mainly all that does is clean the lubricant from the switch. When the switch is put into standby, it is open, and cleaning it will not do anything for an open circuit, and it will not make the switch open any faster.



If the switch work badly you have nothing to loose except some drop of contact cleaner . I do this few times with half success . But switch never be worse after .


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Post subject: Re: Standby Switch Question
Posted: Thu Jun 05, 2014 12:13 am
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stratele52 wrote:
shimmilou wrote:
schnepf13 wrote:

I am not a fan of spraying anything into a switch, because mainly all that does is clean the lubricant from the switch. When the switch is put into standby, it is open, and cleaning it will not do anything for an open circuit, and it will not make the switch open any faster.



If the switch work badly you have nothing to loose except some drop of contact cleaner . I do this few times with half success . But switch never be worse after .


Thanks for the tip -- contact cleaner has been my friend and ally over the years, as well. :) In this case, I don't think the issue is with the switch. It always flips from 'standby' to 'on' with no trouble. And the fadeout when switching back to standby is always slow and gradual. It's not a sudden, crackly cut out as one might expect with a short.


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Post subject: Re: Standby Switch Question
Posted: Thu Jun 05, 2014 8:04 am
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shimmilou wrote:
schnepf13 wrote:
...When flipping on the Standby switch (which I usually do before shutting the amp off completely), it seems to take several seconds for standby mode to fully kick in....


Totally normal. The DC voltage from the power supply caps are slowly discharging through the tubes, and the time that it takes to discharge is dependent on the type of tubes, bias level, and other factors. If you actually timed it, I'm sure that it doesn't really take 30 seconds.

I am not a fan of spraying anything into a switch, because mainly all that does is clean the lubricant from the switch. When the switch is put into standby, it is open, and cleaning it will not do anything for an open circuit, and it will not make the switch open any faster.


I agree, totally normal.


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Post subject: Re: Standby Switch Question
Posted: Fri Jun 06, 2014 7:26 am
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schnepf13 wrote:
Last week, I picked up a used Hot Rod Deluxe at a nice price. The amp works great, but I noticed a (perhaps) unusual quirk when turning the amp off.

When flipping on the Standby switch (which I usually do before shutting the amp off completely), it seems to take several seconds for standby mode to fully kick in. I still get sound from the amp or a 'crackle' from pulling out the guitar cable plug for about 10-20 seconds before the sound gradually, totally fades out.


The HRD standby switch cuts voltage to all main PSU caps. Most standby's cut power to the output tubes, past the first filter stage. So, when you hit the HRD standby, all the caps are still in the circuit. When powering off the amp, you are hearing all of them discharge. In essence, the HRD standby switch in really a "power switch" off the PT's secondary.

When you hit the standby, in say an AB763 Super Reverb (wired like most BF and SF standby's) --- you isolate the two main filter caps from all the other ones. Only, the three or four smaller caps past the two main filter caps discharge, when powering down. Discharge time is usually faster in these caps.

http://bmamps.com/Schematics/fender/hotrod_deluxe.pdf


http://bmamps.com/Schematics/fender/sup ... _schem.pdf


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