5E9 Tweed Tremolux Build Thread: Pics on Page 11

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Re: 5E9 Tweed Tremolux Build Thread: All wired up, no sound

Post by Racing » Tue Sep 05, 2017 12:25 am

Again. Read all of this before heading for the amp again.

Agreed.
Redplating is bad. That is however not the same as that the tube in case is toast. Tubes will take a HELL of a beating before going belly up.

What you do is,as suggested, remove the powertubes completely. As the 5e9 is a cathode bias based amp that means that the two powertubes should share load across a 250 Ohm resistor vs ground,and rather specifically so if they were matched. (Remember that e-cap i asked you to move out of harms way? That´s the cathode resistor in case)
Yank the tubes and fire the amp up. There´s an ever so slight poss that you effed up around the phaseinverter fwiw and this is what to check...

With powertubes out check voltage between each pin 5 and ground. This should read zero volts for both sockets. If not,we have an issue that needs to be remedied.
Turn amp off.
.....as you have fired the amp up sans powertubes it will hold a rather vivid amount of residual voltage as you turn it off and as the e-caps of it are new it will do so for a rather long stretch of time. IOW this needs to be handled before going any further. You need to discharge the amp.
This you do per what has been described previously. A larger ceramic resistor between chassis ground and first hit e-lyte positive leg. ALWAYS measure for residual voltage and do so until content that voltage is below 30VDC. Make sure you´re gripping the resistor you use by its ceramic portion ONLY. Actual resistence value of resistor is of lesser importance.

That done check,physically,that the wires from the output transformer hit each sockets pin 3. Pin 3 is supposed to be the plate. Pin 4 in turn the screen grid,aka g2. Each pin 4 should have its voltage coming from the first resistor in the B+ line,which in this case should be of 2,5k Ohms. If you´ve mixed that up,that can also push the tubes into runaway.
In fact,for g2 it might be a good idea to stray away from the stock schematic by installing a 1k/5w resistor between voltage feed and pin 4 for for each socket to add protection vs exactly what you´re experiencing here.
No. It won´t alter sound in any appreciable manner,just add protection for the powertubes.
As pin 6 is unused for 6V6 and 6L6 both (as EL-34´s) one normally installs these resistors between lugs 4&6 and feed voltage to pin 6.
Second last measurment to do is to check resistence between each powertube sockets pin 8 and ground. It should show around the 250 Ohm mark with amp off and discharged. from each socket individually.
If not,find out why.
Last measurment to pull is to check DC resistence between pin 5 and ground. This is the powertubes gridleaks and thus what establishes bias. They should both show around the 220k Ohm mark vs chassis ground. If not,remedy.
That said..don´t sweat..i bet those 6V6´s of yours to be just fine. Find the culprit for this and we´ll be back on track in no time.

Then.
Yes. Both the cathodes of V1 are supposed to be wired together for a common cathode resistor and small e-lyte vs ground. We need to get to the bottom with this to make the amp work.
Checking resistence values vs ground is done with the amp off and speaking of which...again.....as you have fired the amp up sans powertubes it will hold a rather vivid amount of residual voltage as you turn it off and as the e-caps of it are new it will do so for a rather long stretch of time. IOW this needs to be handled before going any further. You need to discharge the amp.
This you do per what has been described previously. A larger ceramic resistor between chassis ground and first hit e-lyte positive leg. ALWAYS measure for residual voltage and do so until content that voltage is below 30VDC. Make sure you´re gripping the resistor you use by its ceramic portion ONLY.

Amp discharged you measure between cathodes of V1 and ground and should see around the 820 Ohm mark,as has been pointed out.
That said you STILL need to check gridleak resistence vs ground for V1 as well. With an instrument cable inserted into the jacks one jack should show 1M Ohm vs ground and the other approx 140k Ohms (measure from hot tip of cable to chassis ground). If these two measurments are off by any appreciable amount or even measure OL that tube won´t fire as it should. It´s that simple.
We can get into why´s and don´t if you wish but these measurements NEEDS to be taken. Your measurments for gridstoppers are on the mark,so you got the jacks correct per se.

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Re: 5E9 Tweed Tremolux Build Thread: All wired up, no sound

Post by Racing » Tue Sep 05, 2017 12:56 am

Ontopic of screengrids. Aka g2.

This is one of THE most misunderstood parts of a pentode/tetrode et al,why i´ll try to explain what it does in layman terms.

We´ve got a plate..a g2...a g1 (signal and in some instances negative bias voltage) and a cathode. For pentodes we´ve also got a surpressor grid,and atop that we´ve got heaters.

We all know that the tube needs to "glow" before anything happens. Well. For most "modern" tubes the heaters and cathode are kept apart why the heaters are in very close proximity to actually heat the cathode. In short we differ between directly heated and indirectly heated tubes.

As the cathode heats up an electron cloud is omitted from it. These electrons are "active" and wants to meet up with its positive counterpart. In the case of pentodes/tetrodes a rather coarse mesh grille is placed in proximity of it (g2) which indeed attracts these electrons but as the electrons come closer to g2 they notice an even higher potential just a tad farther away. The plate.
This "order" is norm no matter if pentode or beam tetrode. In fact...to an extent the difference them between,from an operations POW,are slim to nil. (Yeeeeeeees..i KNOW this could be argued but i´m trying to make a point here).

That rather large mesh grille that constitutes the screen grid (g2) is never designed to take any appreciable load,which the plate is. The plate of a tube is that rather large grey-ish piece of metal you see first thing as you inspect a tube.
Right.
So WTF does this mean to the novice.? Maximum power rathings for plate and screen grid both can be read from datasheet,which can be found online for basically any tube ever dreamed up,why we ALWAYS download the datasheet for the tubes in case. In there,in plain english,you can find the maximum values,and Ohms two laws apply as always.

Well. For the order of operation to be correct that means that the plate has to be of greater potential at all times (voltage). If at ANY given time the B+ voltage of the plate drops below that of the screen grid...that means that the screen grid TURNS INTO being the plate,and this is certainly no good as the screen was never designed to handle any appreciable loads right (read-amount of watts).

Do i mean to tell you this can happen? That B+ voltage will drop below g2 voltage? Well,it not only can..it will.

As we start making the amp digest power (read-output) voltage will swerge outbound of the powertransformer,or tube rectifier for that matter,dependant of load in a rather dynamic manner. In short it will be all over the place with the music played. This is correct from a transformer design point of view but MIGHT present an issue for g2 if not adhered to.

In fact,from many an aspect as g2 will turn into the point of highest potential we´re sure riding the jagged edge and TBH the tube could even at that point be regarded as a triode. In short,not good. It´s to the point where some designs will run g2 so hard that it melts and collapses,and at that point the tube in case is shot. Garbage.

Hence the need for screen grid resistors. Back in the old days tubes were first of all more sturdy and second of all a dime a dozen so many older designs lack protection for the screens/g2 why it is a good idea to add this to such an older design.

In my case,albeit for other reasons as well,i even go one step further and install zener diodes with a specified voltage drop vs g2. In this manner i can extract the absolute most out of the tubes as the zener diodes are fast enough in operation to actually follow the dips in B+ voltage,thereby securing that g2 voltage at no time can surpass plate voltage,leaving g2 to perform exactly what intended and nothing else.
They DO however impose on sound. Powerstage will turn more "direct" for lack of better description as the transients just isn´t there anymore.

None the less. The 5e9 in essence lack screen grid resistors per se. All that is there is a 2.5k drop resistor for the first hit. Now. Merely installing a 1k/5w resistor per socket will make the amp starved for voltage as load increases why the 2,5k resistor needs to me diminished in value as the 1k resistors are installed to at least retain some sort of balance. Doing so with a 1k resistor will suffice for starters at least.

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Re: 5E9 Tweed Tremolux Build Thread: All wired up, no sound

Post by Racing » Tue Sep 05, 2017 1:13 am

http://www.radiostation.ru/tubes/6V6GT-GE.pdf

Here. Datasheet for the 6V6. Screen dissipation is clearly stated. Ohms two laws,as pointed out,applies. As always.

Speaking of which. JJ´s 6V6´s has been claimed to be 6L6´s in a 6V6 envelope. Having run them through my tracer more times than i care to remember this is false.
JJ´s 6V6´s are indeed exactly that. 6V6´s. They´ll take a rather heavy beating vs "normal" 6V6´s as far as power and plate voltage both though,granted. But they ARE from every other aspect there is 6V6´s. Period.

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Re: 5E9 Tweed Tremolux Build Thread: All wired up, no sound

Post by wproffitt » Tue Sep 05, 2017 5:32 pm

On the original Fender 5E3 circuit/layout drawing pins 3 and 8 are connected, just like on the 5E9.
Scott are you using the original Fender layout drawings or modern versions?

-David, I'm using the original Fender 5e9 drawing but have also employed a modern 5e3 layout (which, you're right, does have a jumper between pins 3 and 8 on V1) which one of my parts suppliers sent as a visual aid for the placement of the resistors, capacitors, pots, and jacks he sent.

One probe should be on earth/ground , the other should be on the valve side of the "25uF capacitor / 820R resistor" .. at the point where the wire(s) come from pins 3 and 8

-Thanks for the tip!

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Re: 5E9 Tweed Tremolux Build Thread: All wired up, no sound

Post by wproffitt » Tue Sep 05, 2017 5:55 pm

Racing,
I won't be able to spend time with this until the weekend, and will have to work through your troubleshooting suggestions one by one then. However, I did notice that you mentioned putting a resistor (1k, 5w) accross from voltage supply to pin 4 of my 6v6 sockets. I did put a 1k resistor between 5 and 6 on these sockets. This is not specified on the 5e9 layout but is (only with 1.5k resistors) on the 5e3. Have I put resistors between the wrong pins here? This IS my first rodeo and seems as though, yet again, I might have conflated thr needs of the 5e9 with another amp.

Thanks,
Scott

P.S. I have not grounded the 6v6s (pins 1 and 2) or the preamp tubes (at pin 9) to the chassis. How stupid is this?

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Re: 5E9 Tweed Tremolux Build Thread: All wired up, no sound

Post by Racing » Wed Sep 06, 2017 1:05 am

Hold it.
Just hold it.

Pinout for 6V6 (which is in the datasheet too)

Pin 2 and 7 - heaters.
Pin 3 - plate
Pin 4 - screen grid
Pin 5 - g1/signal
Pin 6 - Not used
Pin 8 - cathode
Pin 1 - Not used

In other words the ONLY pins that needs to see ground is pin 5 and pin 8. In YOUR case pin 5 should see approx 220k Ohms vs ground through the gridleak resistor. Pin 8 in turn should see approx 250 Ohms vs ground through the powertube cathode resistor. No grounding of ANYTHING else. Heaters will get their ground reference through the heater winding centertap.

Pinout for the novals in use then (read- ECC81/12AT7, ECC-82/12AU7 and ECC-83/12AX7)

Pin 1 - plate for first triode
Pin 2 - control grid for first triode
Pin 3 - cathode for first triode
Pin 4 and 5 are tied together for the ONE side of the heaters
Pin 6 - plate for second triode
Pin 7 - control grid for second triode
Pin 8 - cathode for second triode
Pin 9 - OTHER side of the heaters.

IOW heaters that work with a potential of 6,3 volts (no matter if AC or DC) will be tied to the coupled pin4&5 and then to pin 9. That leads us to that pin 9 is the centertap for pin 4 and 5. This because the TWELVE xx tubes can be run off of 6.3 volts and 12,6 volts both-need be. In your case 6,3 volts why pin 4 and 5 are tied together. So..one heater wire for those two that are tied together and the other heater wire for pin 9.
Download the datasheet for the tubes you use. It´s all in there.

If you put your so called gridstopper resistors between pin 5 and 6 on the 6V6 sockets that´s fine. In that case there should be a wire from each pin 6 on the 6V6 sockets to a 220k resistor each,which in turn head for ground. (One of them via a 6,8k resistor which in turn feeds signal for the farther grid of the phaseinverter.
Phaseinverter type is a paraphase. Read up need be.
You find info on the subject here http://www.valvewizard.co.uk/

Now. The issue here is that the stock schematic doesn´t call for gridstoppers vs the powertubes. This then would be the second strike vs the stock schematic which leads us to a point where it would be a real good idea if you put up a link to the schematic YOU use. Please do.

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Re: 5E9 Tweed Tremolux Build Thread: All wired up, no sound

Post by Racing » Wed Sep 06, 2017 1:35 am

In an effort to try n explain this there with bias.

Point 1/ To a tube the cathode (negative/minus/ground) is the cathode pin of the tube. NOT the chassis. To the tube the world stops RIGHT THERE at the cathode pin. It knows nothing of chassis ground.

Point 2/ Chassis ground is something WE set. This also brings that we very well can,and do,have negative voltages onboard vs the cathode reference of the tube. The tube NEEDS this to be able to set bias and the actual bias is referenced as the difference between cathode pin and chassis.
That brings...try n wrap your heads around this...that for a cathode biased amp,like the 5e9,there will be approx shy 20 volts or so at the cathode pins of the 6V6´s.
THEM approx 20 volts above chassis potential is "zero" to the tubes. The tubes get their chassis reference via pin 5,aka g1. This via their gridleak resistors. Actual "size" (read-amount of Ohms) chosen for these gridleaks depend on a few things. Input impedance for the powertube being only ONE of them.
However.
As cathode pin is zero to the tube that means that the control grid,g1,is 20 volts BELOW the cathode pins. IOW pin 5 is held at a NEGATIVE voltage as far as the tubes knows,and this is how bias is reached upon.
If there´s no chassis reference for pin 5 the tube has NO IDEA what so ever where it is "at" (as it lacks reference) and thus...won´t fire. In short we NEED some sort of chassis reference for g1. That simple. Hence why when in doubt we check to see if there´s reference vs chassis for pin 5.
The higher the difference in potential between cathode pin and chassis ground...the hotter the bias. It´s that simple.

This can be turned around. We can tie pin 8 (cathode) directly to chassis and instead insert a negative voltage (referenced vs ground) on pin 5. We have then converted that 5e9 to what´s known as fixed bias.(As opposed to cathode bias).

Keeping with the 5e9 though... Let´s say you see 20 volts DC between cathodes of tubes (pin eight and ground,and this at a B+ of 360VDC. Ok. Each of them 6V6´s are referenced at 12 watts a piece. IOW 24 watts in total.
The cathode resistor is of 250 Ohms.

Now. Ohms 1st law tells us that voltage=resistence*amperage. U=R*I . Ok. So we know U...which is 20 volts...and we know R,which is 250 Ohms.

20/250= 0.08 Amp
All good.
Now..B+ is 360VDC right.

Ohms second law tell us that power=voltage*amperage. P=U*I
We know that I= 0,08A..and we know U=360
So.
360*0,08= 28,8 watts. In other words 20 volts between cathode and ground is a tad excessive. Mark the word a TAD as bias set to 28 watts instead of 24 watts total for the two tubes won´t send them into runaway.
HOWEVER!
If the one of the two tubes ain´t pulling its fair share that means that the other one does...as we still see almost 29 watts across the cathode resistor as far as the tubes go. In that case scenario we DO have an issue and this needs to be handled.
That we would see such a marked difference between two matched tubes tho is thin...REAL thin....so in such a case scenario always check the "vitals" for the sockets first

So?
For the novice it can be of benefit to have a resistor of 1 Ohm precisely between each pin 8 and the actual cathode resistor. No...that 1 Ohm resistor won´t affect anything but make for a reference point where you can read the actual bias PER TUBE.
If you apply that resistor for the two formulas above you will soon see that a resistor of 1 Ohm will let you read the current draw directly. Ie;the reading taken in millivolts can be directly translated into milliamperes ...as the resistor is of 1 Ohm. Something divided or substracted by one stays the same right...
Put the 1 into the formulas above and you´ll soon enough get the idea.

There´s other ways of measuring individual current draw for the powertubes but these are no doubt more dangerous.

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Re: 5E9 Tweed Tremolux Build Thread: All wired up, no sound

Post by Racing » Tue Sep 12, 2017 2:37 am

Any progress?

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Re: 5E9 Tweed Tremolux Build Thread: All wired up, no sound

Post by wproffitt » Tue Sep 12, 2017 6:48 am

Racing,
Thanks for asking! I'll update you all in greater detail soon when I actually get a chance to break out the soldering iron. Briefly, I'm going to handle a couple of the fundamental areas where I see that my wiring has diverged from the layout drawn by Leo:
1) I need to run jumpers between pins 3 and 8 on V1 and V2.
2) I need to ground my filaments! I glossed over this part of the layout because I somehow imagined that the PT would take care of this, but my PT does not have the green/yellow wire that would typically handle this sort of thing. I'm going to run an artificial center tap by running two 100 ohm resistors from where the heater wires meet the pilot light to my ground on the power side of the amp.

Of course, I'll work through the other suggestions mentioned by you and David, but I need to tackle these first. In the meantime, work and family life are keeping me busy and I probably won't get a chance to do anything until this Saturday. Wish me luck!

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Re: 5E9 Tweed Tremolux Build Thread: It's Alive!

Post by wproffitt » Sat Sep 16, 2017 4:40 pm

...and I'm back! Since we last talked, I
1)jumpered pins 3 and 8 on V1 and V2. I also jumpered pins 2 and 6 on V3 per the original layout.
2) created an artificial center tap for the heater wires using two 100 ohm resisitors wired from the pilot light to ground.

I fired up the amp and it sounds great! It's a real fire-breather compared to my PR. 1-3 on the volume(s) is basically quiet to LOUD! After that, it's basically gritty to "I'm here for the souls of the non-believers" gritty. I'd call the sound a bit more lo fi, and less scooped than my PR, too. With my p90 equipped guitar, it gets gainy really quickly and both volumes are super interactive, so there will be a learning curve for me to dial in the sound I'm looking for. With my Jazzmaster, I cannot get a bad sound out of this amp! It's brighter (of course) and very warm all at the same time. This is going to be fun.

However,
1) the trem does not currently work. A quick look at the layout revealed that after all of this, I've still failed to put in two wires on the "speed" pot! I'll take care of that in the next couple of days. See the picture below for evidence of my buffoonery. The pot in the center with the small resistor attached is the offending party.
2) the second 6v6GT is still red plating. I'll have to look into this with the DMM tomorrow night. In the meantime, I'm using some cheaper Tung Sols rather than the pricier stuff I had in the power section.

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Re: 5E9 Tweed Tremolux Build Thread: It's Alive!

Post by sookwinder » Sat Sep 16, 2017 7:30 pm

... it lives !
relaxing alternative to doing actual work ...

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Re: 5E9 Tweed Tremolux Build Thread: It's Alive!

Post by Racing » Sun Sep 17, 2017 5:24 am

Well done! :w00t:

Told ya... :whistle:

We´ll get to the bottom of that redplaing too...rest assured.

For now tho,congrats! Job well done.

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Re: 5E9 Tweed Tremolux Build Thread: It's Alive!

Post by wproffitt » Sun Sep 17, 2017 4:07 pm

Thanks, Racing and David!
Okay, the trem wasn't quite as obvious as I thought. It's not turning on with the switched pot or the foot switch. What am I missing with the way this center pot is wired up?


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Re: 5E9 Tweed Tremolux Build Thread: It's Alive!

Post by Ursa Minor » Sun Sep 17, 2017 6:24 pm

It's alive!! Congrats! 8)
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Re: 5E9 Tweed Tremolux Build Thread: It's Alive!

Post by Racing » Mon Sep 18, 2017 1:29 am

Not enough info.
Does that orange wire end up at a junction?

How is the other pot wired up?

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