Couple of nice MKIIIs

[NOSValves]

Erik you have no clue what your talking about. The cold resistance of a thermistor does ZERO good until current it drawn through it. Go take a 9V battery and attached a resistor to the plus terminal then measure the voltage on both sides of the resistor they will have identical resistance does nothing without current being drawn. Man this is simple stuff and you still don't get it. Yes I made a slight error in my third statement about thermistors but this was a just a simpe error. You and Shawn for that matter still don't get it which is absolutely hilarious.

I can't believe you would be so stupid not to take my "go away" as meaning go away and leave me alone not leave here......... now go away

Craig

Actually, a resistor across a battery like that has current flowing through it. Your battery will deplete at a rate dependant on that resistance and voltage.

Marvel you mis undestood I didn't say put the resistor across the battery terminals. I said simply attach it to the positive terminal and measure from the negative post to both sides of the resistor or thermistor for that matter. Of course placing the resistor across the battery terminal will drain it and how fast would depend on the value of the risistor.

Craig

[NOSValves]

Oh and Shawn again were talking about VOLTAGE SPIKE as it related to current in this application NOT JUST CURRENT

Just so you know I have a top of the line fluke meter and a $2000 fluke scopemeter... thanks you very much. I wasn't talking about measuring current I'm talking about voltage spike get it through your head. I think I will rename you and Erik the side stepping kings.

Craig

[NOSValves]

Sidestepper Shawn,

Explain why in the Dynaco Mark III amp with a thermistor that I just freshly rebuilt and just got done firing it up, First with a 5AR4 and then a 5U4 I even switched out all the tubes out after the first test to be sure they were all cold! The following is the voltage that the first filter cap was subject too.

With 5AR4 took a full 45 seconds for any B+ voltage to begin to be produced and then it slowly and steadily rose to 410V and then creeped up very slow to 485V

With 5U4 the voltage was there in a split second and just about instantly hit 535V !!!

Oh yes that is real good for a 500V filter can and it would be some what worse without the inrush current limiter. Factor in the amp were discussing here has no inrush current limiter at all. The can is toast and could be gone pretty darn quick.

This is the point of this enitre discussion. Not your techno babble.

Case closed CRAIG IS RIGHT AGAIN.

Craig

[NOSValves]

What no books to tell you why????

[Erik Mandaville]

Craig:

"Case closed CRAIG IS RIGHT AGAIN"

At once very humble and professional.

However, back to this still open case, would you please identify the location of the CL in the circuit to which you are referring? The CL has two leads, and I'm curious about where you have each of them connected. This is an academic question, and I would appreciate it if you might answer in a direct and straightforward fashion. Your explanations lack clarity (for me -- obviously because I'm 'stupid'), and maybe a simple description of the current limiter's location in your circuit would help make all of this less ambiguous. Let's go ahead and chalk this up as just another example of my ignorance, ok?

Erik

[NOSValves]

I'm not explaining anything to you Erik. Get you a tube amp out, Soldering Iron, Thermister, multimeter and play with it. In my book you will learn much more by doing then reading. This is for your own good. Rick and I know exactly why it doesn't work to stop the voltage spike with a 5U4 or SS rectification but does a wonerful job with a 5AR4. Its really to bad you and Shawn can't figure it out.

Craig

[3dzapper]

Erik, The ICL goes in either leg of the AC line in. With an IEC input the easiest place to install it is between the IEC and the fuse in the switch side.

Craig, I still advocate an ICL even with a 5U4 to slow the turn-on current rush through the power tranny, etc. A little insurance for eighty cents.[]

Rick

[Marvel]

I'm not explaining anything to you Erik. Get you a tube amp out,

Soldering Iron, Thermister, multimeter and play with it. In my

book you will learn much more by doing then reading. This is for your

own good. Rick and I know exactly why it doesn't work to stop the

voltage spike with a 5U4 or SS rectification but does a wonerful job

with a 5AR4. Its really to bad you and Shawn can't figure it out.

Craig

Okay. I don't understand.

First, why is the 5U4 an 'instant on' tube? Why does it conduct immediately compared to the 5AR4?

I have other work to this morning, but I may have a second question later.

Bruce

[NOSValves]

Erik, The ICL goes in either leg of the AC line in. With an IEC input the easiest place to install it is between the IEC and the fuse in the switch side.

Craig, I still advocate an ICL even with a 5U4 to slow the turn-on current rush through the power tranny, etc. A little insurance for eighty cents.[]

Rick

Rick,

Yea there is a small benifit to using one anyway and really this is not the point that was trying to be made here. The example I tested last night for these techno freaks has one in place and it doesn't even come close to solving the problem when a 5U4 rectifier is used. Do you know what the voltage spike would be on the amp given such high recomendations here would be? Also factor in that my tests were done with a variac set to 117V imagine what these would be like at some homes that have 125V or more on the wall! I venture to say something in the range of 560V to 580V.... oh yea that 500V JJ can just loves that!! I use in rush current limiters all the time and have for 3 years on amps that have this voltage spike but again with 5U4's or any instant on type rectifier they do little good for voltage spike but they do nock down the actual wall voltage by 2 or 3 volts which can be a good thing. The other benifits your referencing too I think are neglegable since the amp have lasted 45+ years with out ill effect from them.

Oh and just to be sure people understand a 5AR4 without a inrush current limiter will also have a voltage spike in the high 500V range but for a shorter duration then a 5U4. The 5AR4 with a inrush current limiter is a combination that works in these amps to allow safe use of 525V can on the first few stages of the PS and 500V further down the B+ chain. This learned from experience not reading it out of a book.

Craig

[NOSValves]

I'm not explaining anything to you Erik. Get you a tube amp out, Soldering Iron, Thermister, multimeter and play with it. In my book you will learn much more by doing then reading. This is for your own good. Rick and I know exactly why it doesn't work to stop the voltage spike with a 5U4 or SS rectification but does a wonerful job with a 5AR4. Its really to bad you and Shawn can't figure it out.

Craig

Okay. I don't understand.

First, why is the 5U4 an 'instant on' tube? Why does it conduct immediately compared to the 5AR4?

I have other work to this morning, but I may have a second question later.

Bruce,

Check out these diagrams

5U4 Rectifier

5AR4 rectifier

[Painful Reality]

Check out these diagrams

5U4 Rectifier

5AR4 rectifier

Really well schematized info.

Where did you find this?

[sfogg]

" THE POINT IS IN A TUBE AMP NO CURRENT IS SUSTAINABLY DRAWN UNTIL THE HEATERS IN THE POWER TUBES AND FRONT END TUBES WARM UP. "

And that is complete nonsense. The heaters draw more current when the tubes are cold then they will when they are warm.

Not theory, fact.

Measure it since you can't figure out Ohm's Law well enough to know why that is the case.

Then measure the resistance of your InRush current limiter when the amp is dead cold. Turn it on for 10 or 15 seconds (well before the B+ is coming up from your own statement) and then shut the amp off again and quickly remeasure the Inrush current limiter's resistance.

Guess what Craig... it is going to have dropped in resistance by then.

Not theory, fact. I have measured it as posted earlier in the thread. Your flight of fancy about no current draw from an amp until B+ comes up and the tubes are warm is yet another misunderstanding of electronics.

"Just answer this simple question. "

I have answered that question, you are too busy arguing to read the posts. A single resistor (or thermistor) inline with a circuit limits current, not voltage.

"Just so you know I have a top of the line fluke meter and a $2000 fluke scopemeter... thanks you very much"

Then learn to use them and measure the current draw from the wall at turn on with a cold amp with and without an inrush current limiter in them. Then if you like repeat both ways with a 5U4 and with a 5AR4. Be sure the amp/tubes are cold on each power on.

"I wasn't talking about measuring current I'm talking about voltage spike get it through your head."

You have said current surge many times in this thread. If you are talking voltage then use the proper terminology. The whole point that it is called an Inrush *current* limiter should tell you what its use is for. It isn't a voltage clamp.

" Rick and I know exactly why it doesn't work to stop the voltage spike with a 5U4 or SS rectification but does a wonerful job with a 5AR4."

I guess you missed the post were Rick stated:

"That said, a thermister would work best against turn on surges in the power supply if the filament current were to be seperated. The high current drawn by the filaments heats the thermister too fast to be effective on the high voltage seen by the power supply capacitors. Thus there would be no effective protection for that 500V capacitor."

So yes... Rick understands how an inrush current limiter works and what happens with an amp on turn on and is saying the same thing I am. The initial current through the amp is going to heat ICL to the point were it is going to be doing very little by the time the B+ comes up with a 5AR4. Not the exact opposite like you are claiming.

"Explain why in the Dynaco Mark III amp with a thermistor that I just freshly rebuilt and just got done firing it up, First with a 5AR4 and then a 5U4 I even switched out all the tubes out after the first test to be sure they were all cold! The following is the voltage that the first filter cap was subject too.

With 5AR4 took a full 45 seconds for any B+ voltage to begin to be produced and then it slowly and steadily rose to 410V and then creeped up very slow to 485V

With 5U4 the voltage was there in a split second and just about instantly hit 535V !!! "

This has already been explained in this thread. It is from the rectification, it has next to nothing to do with the Inrush current limiter. Take out the inrush current limiter and you will likely see next to no difference in the above measurements at all. You will however see a large difference in the current surge on the amp at power on with either rectifier in place. Measure the resistance of the ICL 45 seconds after power on when the B+ is just starting to come up. According to your posts the ICL won't have heated at all because the amp doesn't pull current until the B+ is coming up so the ICL should still be at its initial cold resistance level. Measure it and you will find that is not at all the reality of what has happened with the ICL.

Shawn

[NOSValves]

Your wrong Shawn give it up. The amperes the tubes heaters draw as in 1.5 amp per output tube is not what the actual wall voltage is presented with in amps the turns ratio of the transformer is in-between. Once again I'm amazed at how technical you write but how little you understand. All the heaters in a Mark III add up to about 2 to 3 tenths of a amp drawn from the wall because of this small current the inrush current limiter doesn't heat up that much at all. A Mark III completely warmed up with the B+ humming away only draws about 1.1 Amp off the wall. The B+ amps drawn are 3 to 4 times more at the wall then the heaters. So when this tremendous amount of current that the B+ starts drawing as the filaments warm up on all tubes in the amp through the thermistor then the thermistor again holds the current back until it comeptetely heats up. It does the same thing with a 5U4 but it does it TOO LATE and TOO LITTLE. Its just too hilarious you don't get any of this! Keep it up your making a complete fool of yourself. God if I only had the technical writing abilities to go with my technical experience you would be literal toast!!

Craig

[NOSValves]

Jeff,

I get it through TDSL desktop program from Duncan Amplification under Data sheets links. I'm sure you have used the program before you just haven't run into these drawings. The Frank Phillipse links have them. It's not available on all tubes but it is pretty cool.

Craig

[Piranha]

I am really confused. Can you guys do me a favor and lay all this out in terms a complete novice would understand?

[NOSValves]

I am really confused. Can you guys do me a favor and lay all this out in terms a complete novice would understand?

Don't ask Shawn he only knows Techno Babble. Don't ask me I can only write Gibberish, Don't ask Erik he has no clue one way or the other. Maybe Rick can put it in laymen terms that everyone would understand. But really who the hell cares, it is what it is ......... with a 5U4 rectifier or any instant on type it will not solve the voltage spike problem. I have no clue why anything more even needs to be said.

Craig

[sfogg]

Craig,

" The amperes the tubes heaters draw as in 1.5 amp per output tube is not what the actual wall voltage is presented with in amps the turns ratio of the transformer is in-between."

Never said it was. I said it draws 1.5 amps (hot) at 6.3v. When cold they will draw 9 amps at 6.3v. That is for an EL34. A 6550 draws 1.6 amps hot at 6.3v.

Of course one could convert the above to watts (well maybe you couldn't) then go back to amps from watts @ 120v if they so desired.

If one was to do that they could point out that your claim of 1.1 amps off the wall for a fully warmed up MKIII is proving my point, not yours. The heaters in a pair of EL34s when cold will be drawing nearly 1amp *by themselves* from the 120v AC and that is assuming no looses in the heater circuits. Add in the draw from the 5AR4 heater and the small signal tubes and you are already above 1.1amps at initial turn on. So as has been explained to you you are proving the point that at initial turn on is when the current surge of the amp is highest. When everythng heats up and settles down the current draw from the amp is lower.

Not going to bother to show you the techno babble on how to determine that as it is obvious you wouldn't understand it anyway.

" because of this small current the inrush current limiter doesn't heat up that much at all."

Wrong. Measure it.

Unlike you I have actually done that.

After roughly 10-15 seconds on a MKIV the inrush current limiter has already dropped from its initial cold resistance of 26 ohms to about 8 ohms.

Shawn

[NOSValves]

Bullsh!t Shawn just be a man for once in your life and admit your wrong. Come on its a uplifting experience.

Craig

[Marvel]

The B+ amps drawn are 3 to 4 times more at the wall then the heaters. So

when this tremendous amount of current that the B+ starts

drawing as the filaments warm up on all tubes in the

amp through the thermistor then the thermistor again

holds the current back until it comeptetely heats up.

Craig

This can't be right at all. That all comes off the high voltage winding

and on a Mark III transformer, it only supplies about .2 amp (200 ma)

on the output windings. One heater reuires more current than that. The

heater on a single KT88 is eight (8) times higher than what the high

voltage secondary could provide.

BTW, explain what the drawings are supposed to tell me.

[NOSValves]

Marvel,

Trust me your not understanding the operation of the transformer. My writing skills are limited. But I will try to explain.

The heaters are at 6.3V and 5V the transformer starts out with 120V so the transformer is reducing rather then raising the voltage. So when you factor in the turns in the transformer the amperes used are less at the wall then the heaters actually use in the amp by a huge division! In the 5V case you divide by 24! in the 6.3 volt you divide by 19 using 120V as the wall voltage. With the B+ the exact opposite is true the transformer is raising the voltage so the entire equation is reversed. The B+ draws at least 3 to 4 times more current off the wall. The mathematical equation like Shawn mentioned (but doesn't understand) is longer then this but regardless the end product is the same.

I have no clue where he comes up with this 9 amp at startup with a EL34 but if it is indeed true I bet it lasts for a quick milli second because my Fluke sure never shows this heavy current spike that he is talking about. In fact if this 9 amp figure was true then how the hell could any transformer ever last in the tube amp for instance the ST70 6.3V winding is only rated at 5 amp for the pair of EL34's and one 7199 how the heck would that work?? The Mark III is also at 5 amp for a pair of KT88's and a 6AN8 driver tube.

Craig