Loud pop when switching standby to off..

wildebassman · Post by **wildebassman** » Tue Oct 27, 2009 5:54 am

I'm really happy with my JTM45 and all is working great but there's one thing that puzzles me. Sometimes when I've had the amp on, and stopped playing for a few minutes, when I switch the standby to off there's a loud pop. Is there a a way to cure this and what causes it?
Please help out.

Cheers,

Dennis.

MBD115 · Post by **MBD115** » Tue Oct 27, 2009 7:55 pm

Popping noise when going to standby? We all had popping noises when coming off of standby....

Do you have the 5.6k grid stoppers installed? Those fixed my amp!!! But my noise was the other way I guess.

Good luck

zrAC/DC · Post by **zrAC/DC** » Tue Oct 27, 2009 7:57 pm

My amp has an occasional pop when turning the standby off, I'm not really too worried about it. I figured the only reason the amps squeals when turning the standby to on is the Valve Arts, my amp stopped doing it when I switched over to the Gold Lions, they are a whole different beast as far as sound goes.

Wayne · Post by **Wayne** » Wed Oct 28, 2009 12:23 am

Hey.

This is a common problem. What you need is what i think is called a "snubber" cap. It's a 0.047uF cap connected to the standby switch / pin 8 of the tube rectifier. This layout (from a competitors website) shows the way it's connected.

https://taweber.powweb.com/store/6m45_layout.jpg" onclick="window.open(this.href);return false;

Top left of the layout right at the standby switch to ground. It just suppresses the "back lash" you get when you switch the rectifier - which is what gives you the "thunk" through the speakers. You see this type of thing on tube rectified amps and also on JTM45/100's.

Wayne

LJay942 · Post by **LJay942** » Wed Oct 28, 2009 3:58 am

Mine does this too. I didn't think it was too big of a deal though. What voltage rating would you say for the capacitor on the standby swithc?

Wayne · Post by **Wayne** » Wed Oct 28, 2009 5:12 am

That's the B + so anything above this voltage value. 500v should do.
Wayne.

wildebassman · Post by **wildebassman** » Wed Oct 28, 2009 12:16 pm

Thanks, after searching the forum I also found a solution that is even simpler:
http://forum.metroamp.com/viewtopic.php?f=15&t=12881" onclick="window.open(this.href);return false;
Read Larry's (Novosibirs) input on the subject, pretty simple fix.

Thanks for the help guys!

Dennis.

Wayne wrote:Hey.

This is a common problem. What you need is what i think is called a "snubber" cap. It's a 0.047uF cap connected to the standby switch / pin 8 of the tube rectifier. This layout (from a competitors website) shows the way it's connected.

https://taweber.powweb.com/store/6m45_layout.jpg" onclick="window.open(this.href);return false;

Top left of the layout right at the standby switch to ground. It just suppresses the "back lash" you get when you switch the rectifier - which is what gives you the "thunk" through the speakers. You see this type of thing on tube rectified amps and also on JTM45/100's.

Wayne

PCollen · Post by **PCollen** » Thu Oct 29, 2009 4:21 pm

w/r/t the "snubber cap" :

I had the popping problem when putting the amp into STBY before powering in off, and I solved it by REMOVING the .047uF "snubber cap", which I had soldered directly to the output (tube socket pin) of the rectifier and grounded on that tube sockets mounting screw, not to the STBY switch. Since I removed that cap, I've never had popping again. (Note:
my B+ is 410Vdc by design..I like the lower voltages in my amp. The cap was rated for 600 Vdc , AIR).

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Loud pop when switching standby to off..

Loud pop when switching standby to off..

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