HV filtering using stby switch

[dude]

I was adding an extra filter in power supply to protect tube rectifier but with a stby switch with a filter before to protect rect tube and a filter after stby, would hit the rect tube with two filters in parallel when stby is off and HV going to amp. Ex: 40uf before, 40uf after is 80uf, not good for a 5AR4, 5U4 and many other rectifier tubes. So, if a 40uf filter is on pin 8 of a 5AR4, with stby on the tube is protected, turning stby off suppling HV to amp, one should run to the choke first, then to node A, B, etc? What is the proper way to wire power supply with a stby switch and rectifier tube, using a choke and without...?


Looking at the Deluxe single channel Lite, the schematic shows the stby between the 40uf and choke. So does the layout but their is a second layout of power supply, what does that pertain too?
Again, not too the muddy the waters but many brand name manufacturers have a stby switch and no cap before the switch using a rectifier tube, confusing.

[pdf64]

I find the language / terminology around standby switches confusing, things need to be phrased carefully for the meaning to be clear.
eg if standby is ‘on’, is the amp able to operate or not?
I suggest to describe the 2 states as being ‘standby mode’ and ‘operate mode’.

Really, it would be useful to know
1/ what benefit do you perceive from the facility to put the amp in standby mode?
2/ what benefit you perceive from splitting the reservoir capacitor in two, so that one part is unswitched, the other ‘hot switched’?

See http://www.valvewizard.co.uk/standby.html

[d95err]

Please post a simple schematic of what you’re planning. It’s too complex to understand from just words.

Just draw on paper and take a picture of it with your phone.

[shooter]

I suggest to describe the 2 states as being ‘standby mode’ and ‘operate mode’.

that would be nice, but you can only lead musicians to water, it's against the law to drown 'em 

[dude]

Yes, stby switch is confusing, if you look at most bigger Fender blackface amps, when stby is in off position, no  DC HV to circuit, when on current flows. So, on means switch is made, amp plays.
As far as my question, l though l’d get an answer, maybe there is no correct answer..? Conclusion is a lot of BF amps with STBY switch, have no big filter cap before but a coupling cap, usually .05uf@630v, is this protection for the rectifier tube? Several builders here who use a STBY switch, have a filter before and choke after, so all I asked “is any filtering needed before STBY to protect the rectifier tube” , is the .05uf cap used in BF amps sufficient, and if a filter cap is used before STBY is a choke then needed after and what if the amp doesn’t use a choke? I thought l’d get some advice, maybe l’ve asked too many ridiculous questions in the past, l was not educated in electronics.  I do a lot of conversions, organ donor builds, etc. that l use a STBY, just want to do it correct.

[sluckey]

Having a filter cap connected directly to a tube rectifier is a good practice. It prevents a high surge current when a STBY switch is placed in the operate position. This high surge is harmful to the rectifier tube and sometimes results in arcing inside the tube which usually leads to a shorted tube, which leads to damaged filter caps (or worse). Fender soon realized this and began connecting filter caps directly to the rectifier.
 
You need to study the different era Fender amps. Fender used a .05 cap prior to the STBY switch ***ONLY*** in the 5 series Tweed amps. When they changed to the 6 series Brown Face amps they dropped the .05 and used big electrolytic caps prior to the STBY switch. This carried on with the Black Face amps as well.

Spend 30 minutes looking through the Fender section of Hoffman's schematic library and you will soon have the answers to all these questions.

[dude]

Thanks, l have one question that won’t be answered by searching, if l use a standby (big filter before) but no choke after, l oblivious don’t have another big filter get hit with HV. So, without using a choke the current goes to OT and “what”?


“The OT and first rail resistor then the B node, resistor, C node, resistor, etc.”

[sluckey]

resistor

[sluckey]

See, you already knew that. Just had to stir the mix so it would float to the top.   

[dude]

Right, the cream of the crap. Sometimes I have to sit back, think a bit, then  electrocute myself, 

[Ed_Chambley]

I suggest to describe the 2 states as being ‘standby mode’ and ‘operate mode’.

that would be nice, but you can only lead musicians to water, it's against the law to drown 'em 

This is true unless the musician is also a goof ball electronics nerd.  When I must install one, common problem on older Fender is switches are not fond of DC.  So I call one the AC switch and the other DC switch.  And I say in the alphabet A comes before D, always has, always will.


Now, if I were you I believe I would just leave the DC switch on all the time, but it is your amp!  You are more impatient with warming up your girl than you amp.  Musicians (customers) hard to find good ones anymore!

[sluckey]

Gotta get a Honda girl. Guaranteed to start on the first pull!   

[shooter]

 
I had a '70s Honda Elsinore (sp?)  She was crankier than a wild hog with teething piglets 
 

unless the musician is also a goof ball electronics nerd

always exceptions to the willing 

every system I worked on had a standby switch, as pdf64 pointed out we always used standby and operate, always pay more attention in operate 

 

[dude]

Ok, in Sluckey’s and Dougs 6V6 Plexi, they have no STBY switch, l an using one. To protect my 5AR4 in my Plexi from surge l put the stby side from pin 8, to the first 32uf in my 32/32 filter can, this filters my rectifier tube only when stby is closed. The other side of the switch (B+ side) goes to the choke and OT, then down the rail from the choke. Now to put back my 220k bleeder, if l put it on the 5AR4, pin 8 side to ground, it bleeds the just one of the cans filters when l turn off stby. To bleed the other filters when off, l’d have to leave the stby on when amp is off. Hope this makes sense, l could draw a schematic if l’m unclear here.
I could use two bleeders I guess, one on each side of stby switch so if one turns off both on/off and stby, all filters bleed current to ground.
I have several of these amps made for friends, they will just turn off both switches but might get shocked thinking the one bleeder is draining all caps. Need advice, am l out to lunch. Can o use just one bleeder and if so where would it go?

[shooter]

Need advice

just did a random look at fender schematics, (they like standby switches:), Leo didn't seem to be concerned about bleeders in the examples I looked at.  As someone that stuck my hands in lots of places with big B+ I NEVER went in without a shorting bar no matter how any bleeders the schematic showed, guessing the Fender techs do the same 
you should be able to add bleeders about anywhere, keep the R's big kohms.

[sluckey]

dude, use as many bleeders as you like...

[dude]

Nice, wish l could figure out that program, guess like anything, takes more commitment. Yes, that’s my power supply just the OT CT is not drawn, goes to input with choke. Thanks Shooter and Sluckey, now l know why you guys don’t use standbys, don’t need them, , pain in the a**.


Repairing, building, designing amps just takes a little reasoning once you know the basics. So many ways to skin a cat or build an amp. To “skin a cat”, sounds terrible, l never would. Wonder where that saying came from....

[sluckey]

Yes, that’s my power supply just the OT CT is not drawn, goes to input with choke.

Haha! In my haste to post that pic, I forgot to put Node A on the other side of the switch. Sorry.

[dude]

You taught me well

[shooter]

To “skin a cat”, sounds terrible

enough spices they taste ok, had some in North Africa, might have been dog, there was a pretty big language gap 

[PRR]

> So many ways to skin a cat or build an amp. To “skin a cat”, sounds terrible, l never would. Wonder where that saying came from....

There's more than one way to coin a phrase; but I think it came into American through Mark Twain.
A Connecticut Yankee ...
https://grammarist.com/phrase/more-than-one-way-to-skin-a-cat/
https://www.bnd.com/living/liv-columns-blogs/answer-man/article181298616.html
https://english.stackexchange.com/questions/32123/origin-of-the-phrase-theres-more-than-one-way-to-skin-a-cat
https://www.vice.com/en_us/article/wnj9e4/how-many-ways-are-there-to-skin-a-cat

[kagliostro]

To me it is only a colorful way of saying

For a thing very difficult to be done

here we can say

a (female) cat to be peeled

and referring to something is better not to do before you are on the conditions to do it

here we can say

Don't sell the bear's skin before you've killed it

But no one is thinking to really skill a cat or kill a bear

Franco

[dude]

Thanks for the info, on skinning a cat, especially PRR, interesting reading and probably came from Mark Twain.
Finally found the cause of some arching in my 5AR4 when turning STBY on and why a relatively new 32/32uf  can went bad and started smoking but didn't blow. I had a 5 watt 22k flame proof R for a bleeder on the can that blew, not 220K. I measured the resister with a cheap automatic meter, it did measure 220K.  But: the meter's dial had 200K setting then went to 2 Meg, on the 2 Meg it said .220K, so I figured it was 220K, auto meter. When I was rewiring the power supply as Sluckey's drawing he kindly drew for me, I notice that bleeder was a red, red, black, red, that's not 220K as when I was installing the second bleeder it was red, red, yellow, which I knew was 220K. I looked up the black band, the multiplier, the Resistor was 22K, not 220K. No wonder the cap smoked, it lasted a few months too at 22K, now with the proper 220K bleeders I think I notice a difference in tone too???  Anyway, the Chinese auto range meter keeps reading "nly that resistor" wrong, my BK reads it at 22K but it's manual.  Maybe something to do with flame proof?
I think it pays to get a quality meter, hope I didn't damage the 5AR4, it is a Muller, made in England. Wonder why that meter only read that resistor wrong and all others I check correct....?


Live and learn and pay attention to the bands   

[sluckey]

I doubt that 22K resistor had anything to do with the cap can failure or the 5AR4 arcing.

[dude]

You would know that better than I, 22K is kind of low for a bleeder. Once in a while I would see the 5AR4 flash inside when STBY was switched from closed to opened, I want to say on, can get confusing whether "on" means closed and "off" means open. But the way Fender did it was the light was "on" when switch was opened, "off" when closed. So, they felt "on" means amp plays, switch open. Anyway, thanks for your help. Curious why you, Doug, and many others don't add a STBY. I guess the only reason for it would be to have the amp ready at a flip of the switch, but many times I had forgot to turn the amp off, sat overnight on, probably not good for the rectifier tube.

[sluckey]

Hmm. You have a 47µF cap tied directly to the rectifier tube. Then you have another 32µF cap on the other side of the STBY switch. That puts 79µF on the tube when switched to operate. Not good for the rectifier tube.

This probably explains the tube arcing.

As for standby confusion, if you always say standby/operate then everybody will know exactly what you mean. Doug and I built our 6V6 Plexis in a 12" long chassis. Not much room for a STBY switch! Not that I would have used one if there was plenty of room.     All I've built lately is small amps that I don't feel need a STBY switch, especially in my living room.

[pdf64]

...Curious why you, Doug, and many others don't add a STBY. I guess the only reason for it would be to have the amp ready at a flip of the switch, but many times I had forgot to turn the amp off, sat overnight on, probably not good for the rectifier tube.

Guess you haven't got around to reading the valvewizard link? I suggest that you would find it beneficial to do so, as it answers all the queries you've been raising.

[dude]

Guess you haven't got around to reading the valvewizard link? I suggest that you would find it beneficial to do so, as it answers all the queries you've been raising.

Ok, read the wizards take, good info. I usually do put two diodes before the rectifier tube. I, like others were introduced to STBY early in my amp tinkering. I assume you have no standby switches in your builds. BTW, was that you in the Lucky song, reminded me of Buddy Holly, except the leads, nice. Your drummer is pretty good too.

[Colas LeGrippa]

IMHO a rectifier tube should never be put on stand by. Switching it on and  off from the circuit will shorten it s life. I destroyed ALL OF MY 5Y3 and GZ34 's in my builds  even with right capacitance, according rto the datasheet.


Now, I lower my guitar volume pot completely and since I use no pedal of any kind, it turns the amplifier dead quiet. There are other ways to cut the sound of an amp like disconnecting the guitar jack at the amplifier, sending the guitar signal to gnd with a switch etc.


Merry Christmas to all !