Loud POP - Stand By

[raza]

Hi I have a problem! 


I have a big POP on the stand by switch.

I try yo put a 100k resistor (5W) between switch but... no look!


What do you think?


Regards!

[pdf64]

It’s trying to tell you how conceptually pointless it is 
Let the rectifier to its thing.

[Leevi]

There is no CT in the transformer? Is it  correctly drawn?


/Leevi

[Latole]

Most of the time I fix it with 0,0047 mfd in parallel with the switch.  Or a sometimes it is a bad switch.
 
On a Fender Bandmaster I never find the issue.

[raza]

Yes it have center tap, is quick draw.

I am going to try the 472 cap. With the resistor or without?

[Bieworm]

How about just letting it pop? Who cares?

[raza]

I tryed the cap un parallel with the switch and no changes, pop!
Also try the cap with resistor and POP!

It's a bit loud.

[sluckey]

Put a zero ohm jumper across the switch lugs.

[Leevi]

It will probably not help but try to move the switch after the rectifier I e. before the first filter cap.


/Leevi

[pdf64]

It is poor practice to ‘hot switch’ a capacitive load on to a valve rectifier   

[Latole]

I tryed the cap un parallel with the switch and no changes, pop!
Also try the cap with resistor and POP!

It's a bit loud.

On a Fender Bandmaster I never find how to fix the loud POP

[Latole]

Read this post few months ago about switch loud pop:


https://el34world.com/Forum/index.php?topic=26658.0

[Leevi]

It is poor practice to ‘hot switch’ a capacitive load on to a valve rectifier   

You are right, it will stress the rectifier tube.


A solution that has worked is visible in the following schematic.
It means an extra filter stage but if you want to get rid of the POP...


http://i301.photobucket.com/albums/nn73/Nathan_C/Atonic2.jpg


/Leevi

[pdf64]

It seems something of an exercise in pointlessness though?

[Latole]

It seems something of an exercise in pointlessness though?

 Video not available in my country, Canada 

[sluckey]

There is no video. Only jpg pic.

[Latole]

There is no video. Only jpg pic.

No jpg pic. only many videos advertising on the screen

[John G]

hI,
a COUPLE OF THINGS TO TRY.
bOOGIE INSTALL A HI VOLTAGE SMALLISH VALUE CAP(.1Uf )To ground on the down stream side of the STB switch.


Maybe move the STB switch to the centre tap of the transformer ??
my 02 cents worth.
John

[pdf64]

...Maybe move the STB switch to the centre tap of the transformer ??

That would create a ‘hot switching’ scenario. 

It would be beneficial to have an insight into exactly what raza wishes to achieve with the standby.

[John G]

Hi,
Then....................................maybe put the 100k resistor across the center tap stb switch...............


Use a timed rectifier tube and eliminate the sty switch.


Cheers,
John

[66Strat]

Seems like a lot of effort to remedy the solution to a non-problem. 

[pdf64]

...Use a timed rectifier tube and eliminate the sty switch...

That’s what a GZ34 does.
And then a standby switch gets added.

[Latole]

Seems like a lot of effort to remedy the solution to a non-problem. 

We could call it being a perfectionist and that's how things often get better.

[pdf64]

But why put devote resources to improving, nevermind perfect, a feature that is conceptually nonsensical?
A vehicle with square wheels will inevitably have a bumpy ride, not matter how its good suspension. 
The drawbacks (ie damaging / unwanted effects) of HT standby are most easily and effectively eliminated by eliminating the feature.
Any actual benefits / desirable features are more simply achieved by other means.

[PRR]

It's not clear why a push-pull amp would have a LOUD pop. Is the power stage grossly unbalanced? Dead tube?

[Leevi]

I have now similar issue with my new Bassman 59 clone.


This unit across the standby switch solved the issue.


https://cdn-reichelt.de/bilder/web/xxl_ws/B300/KEM_PMR209_01.png



/Leevi

[HotBluePlates]

It's not clear why a push-pull amp would have a LOUD pop. Is the power stage grossly unbalanced? Dead tube?

Not that I've seen.  The puny amps (including single-ended ones) didn't get standby switches, and the big push-pull amps always wind up with their standby popping.

I might have gotten rid of every amp I had with a standby switch.  When I did have some, I never used it to kill B+ in an amp but just left them in Play mode.

[Leevi]

I might have gotten rid of every amp I had with a standby switch.  When I did have some, I never used it to kill B+ in an amp but just left them in Play mode.

I don't like the standby switches either but if customer wants one I will do it. This time in a traditional way.
Popping standby is not an option.


/Leevi

[pdf64]

I have now similar issue with my new Bassman 59 clone.

This unit across the standby switch solved the issue...

Although snubbing the switch contacts stopped the ‘pop’, grossly excessive peak anode currents from hot switching the rectifier will still occur every time the standby switch is flipped into operate mode.
Why subject your rectifier to that?

[Leevi]

Although snubbing the switch contacts stopped the ‘pop’, grossly excessive peak anode currents from hot switching the rectifier will still occur every time the standby switch is flipped into operate mode.Why subject your rectifier to that?

I understand the concern and fully agree with your statement


/Leevi

[pdf64]

A couple of my friends / acquaintances in gigging bands whose amps I maintain also insist on retaining and using standby, so I empathise 
I persuaded them to accept what seems a ‘least bad’ option, which inserts a high value (10k 3 or 5W) shared cathode resistor in standby mode.
Thereby taking high voltage off the switch, pretty much eliminating surge currents / voltages (hence no pop), and saving a bit of wear on the power valves.
The output is reduced to a whisper, ‘sleeping baby in the next room’ kinda level, but it’s not a complete mute, which is the main sticking point for the users.
A DPDT switch could be used to short the signal in standby mode to achieve that, but it seemed inelegant and an inevitable lead dress compromise to resort to that.
Note that for cathode biased amps, the bypass cap should be arranged to bypass both the regular cathode resistor and the ‘standby’ one, in order to keep it charge and so avoid a current surge through the power valves when flipping to operate mode to the charge up the cathode bypass cap. If not already, a higher voltage, eg 100V, bypass cap would be needed.

[Leevi]

Good, have to keep in mind. I have spend lot of time with standby switch issues.
One concern of the standby switch is the high voltage which is often more than 450V.
Normally the switches are specified for 250V in Europe.


/Leevi