5E3 Rectifier voltages

[mayburyds]

Hi,


I'm getting confused with voltages again!


Have a NOS GE 5Y3WGTB installed in V5.


The voltage from the mains is 248v.


The secondary voltage from the PT is 340v measured on the tube.


The B+ voltage measured on the tube is 370v.


If I switch to a TAD 5Y3 then the secondary voltage is 340v measured on the tube.


The B+ voltage measured on the tube is 399v.


The TAD spec says that the PT should idle with a B+ at 350v.


Are such big differences between the secondary and B+ just across the tube normal?


Cheers.

[Willabe]

I'm getting confused with voltages again!

No your not, it's the tube and the load.   

The TAD spec says that the PT should idle with a B+ at 350v.

When they say 'idle' that infers a specific load. But in what amp with what load?

If you give any rectifier tube a heaver/bigger load the B+ will be lower. If you give it a lighter/smaller load the B+ will be higher.

All tube rectifiers have an internal resistance, all tubes do. Just like with a resistor if you pull more current through it will drop more voltage.

The Tad 5Y3 is not a real 5Y3 and has less internal resistance then a real 5Y3, so it's dropping less B+dcv.


                   Brad      

[John]

If I understand what you're saying, that sounds normal to me. Your rect. tube is also a resistor. I think the NOS 5Y3 is around 400 ohms (could be wrong, too lazy to check for sure) The newer 5Y3 (which is not considered a "real" 5Y3) doesn't have as much internal resistance, so your B+ will be higher.

[mayburyds]

Thanks for the replies.


I understand that there is a difference between the NOS rec and the TAD rec.


Just taking the NOS rec, I guess what I'm asking is why does the voltage increase from 340v going in and 370v coming out and is it ok that it is a difference of 30v? No guitar plugged in and all controls down.


Looking at the schematic of the 5E3 that SLuckey built the rec has 340v in and 350v out. Is the difference between the rec that SLuckey uses and the rec in my amp?


Cheers.


 

[sluckey]

The secondary voltage from the PT is 340v measured on the tube.

The B+ voltage measured on the tube is 370v.

I guess what I'm asking is why does the voltage increase from 340v going in and 370v coming out and is it ok that it is a difference of 30v?

The 340V is RMS AC voltage. The 370V is DC. So you cannot directly compare the two values.

Convert the RMS AC to PEAK AC first by multiplying by 1.414. So, 340VAC _RMS is the same as 480VAC _PEAK. The rectifier tube operates on this peak value, not the RMS value.

[mayburyds]

Yep, forgot one is AC and the other is DC 


But why does my NOS rec diff in the DCv out (370v) to the rec (350v) on your schematic?


Cheers.

[mayburyds]

Ok, thanks for the replies.


Think I've seriously gone off vintage stuff!


Too many variables involved to ensure you can get a good result 


Cheers.

[sluckey]

But why does my NOS rec diff in the DCv out (370v) to the rec (350v) on your schematic?

First off, there is no 350V shown on my 5E3 schematic. My HT secondary is 330VAC and my B+ is 340VDC.
But, a 20V difference is nothing when you are talking about 350 or 370. I'd say you're good to go.

[Willabe]

But why does my NOS rec diff in the DCv out (370v) to the rec (350v) on your schematic?

If their both 5E3 amps and have the same tube count, no extra tube/circuits and the wall ac voltage is pretty close, then it's that the PT's are different.

Sluckey's PT is probable has a little more B+ secondary current available and/or more B+ filtering.

Think I've seriously gone off vintage stuff!
Too many variables involved to ensure you can get a good result 

Has nothing to do with 'vintage stuff'. It has everything to do with Ohms law. B+ supply and demand. 'New stuff' will behave exactly the same as far B+ dcv, ohms law and supply and demand, even solid state.

Most guys here will tell you that with a B+ of 350dcv to 370dcv you wont hear any difference. I wouldn't worry about it.


                     Brad        

[mayburyds]

Brad,


My problem is I don't know or understand enough.


The more I read the more questions get thrown up and it doesn't seem to be an exact science, the formulae might be but when you start seeing 10-20% variances it makes you wonder how anything works!


Cheers.

[Willabe]

Maybe my amp is biased a little hotter? But, a 20V difference is nothing when you are talking about 350 or 370. I'd say you're good to go.

And/or; If you both used the same 250 ohm cathode bias resistor it could be that Sluckey's 6V6's are drawing a little more current. All tubes will draw different amounts of current. That's why Groove tubes gives tube (current) ratings from 1 to 10 if you order from them.

If you order matched power tube sets from other venders, whether NOS or new production, they will have a current draw # on them, like 31mA or 37mA.

The 5E3 is a cathode (K) bias amp and is not as easy to adjust the bias on K bias amps as it is on grid bias amps. It can be easer to just change tube sets (if you have enough of them) then fiddle with the K resistor.

But like Sluckey said your good to go, your B+ dcv is not far off at all. As long as your 6V6's are not red plating your fine. And their not red plating because if they were they would be pulling too much current and the B+ dcv plate voltage would drop a LOT.

I'm not the best at math but, I think, 350x10%= 350x 0.1=35. So the difference between your B+ and Sluckey's is 20v which is less then the 10%#. Lets try, 350x 0.06=21, so your 2 amps are a ~little less then 6% difference in B+ plate dcv?


                   Brad     

[labb]

Take a look at any of the layout drawings for the old Fender amps and there will be a note that says voltages are taken to ground and are + or - 20%

[Willabe]

My problem is I don't know or understand enough.

We understand that and we're trying to help you understand more.    

The more I read the more questions get thrown up and it doesn't seem to be an exact science

Part of it is exact and part is not but Ohms law (laws of physics) don't lie. But do we really need to be exact all the time? The engineers who designed the tubes and transformer need that depth of tolerance in exactness but because of their work we don't have to worry about it as much. As long as we don't do things like drastically over voltageing the tubes or drawing to much current from them or the PT/choke or over powering the OT or speaker(s) we're ok. We just don't want to blow things up or drive things so far to the edge that they have a very shortened life.

I'm a carpenter, I 'need' to use the right tool for the right job, bigger nail, bigger hammer. Some (smaller) saws I have will cut large/thick pieces of lumber but if I do that all day I run the risk of over heating the saws motor and it will go up in smoke sooner than latter. 

Keep reading and keep asking questions and it will start to soak in and make sense to you. Be a little patient with yourself, you'll get it but there's a lot to learn and it will take time. It's just life and we all are in the same boat.   


                       Brad     

[mayburyds]

Brad,


Understood


What I'm trying to sort out with my 5E3 is the brittleness / harsh sound it has when full on. It stills sounds great at lower volumes but not what my understanding of how a 5E3 should sound. SLUCKEY summed the sound up when he told me to keep turning the controls till I get that Honky Tonk Women opening tone. My amp is miles away from that tone.


It is getting a bit better each change I make which have so far been -


Swap the rec out for a NOS one
Use the 240v tap instead of the 230v tap
Swap the TAD 6V6GT for Tungsol 6V6GT RI


I've also installed a VRM kit not to solve any tone issues but volume ones!


The speaker is a Jensen P12R 25 watt.


What lead me down the voltage route again was when I put back the TAD rec the harsh sound got worse.


I then read a review of a Torres Tweed Deluxe. The review model seemed to suffer the same harshness I'm experiencing. The thoughts here were the new valves and the use of orange drop caps may be the issue.


Here's the report if anyone is interested -


http://www.performing-musician.com/pm/nov07/articles/torrestweed.htm


Back to researching and reading!


Cheers,


David.


 

[mayburyds]

Quick update -


Put a 5751 in V2 - reduced the harshness to livable but the volume went down a bit aswell.
Put the 5751 in V1 - as above but the volume didn't drop as much.
Put the 5751 back in V2 and put the TAD rec in - harshness back.


So right now the Philips 5751 is V1, the TAD ECC83 in V2, Tungsol 6V6GT in V3 & V4 and the NOS GE 5Y3WGTB rec in V5.


I'll live with that combination for a bit and see how it goes.


Cheers,


David.

[sluckey]

Do you have some different speakers you can try? I have a reissue P12N in mine and it's really a little brighter than I'd like, but I have never tried another speaker. I believe the P12R is a bright sounding speaker also?

[mayburyds]

Funny that I've just been looking at speakers!


I have a Celestion G12P-80 lying around, a Eminence FDM Maverick and an Eminence "special" from my BDRI. Not sure if they are suitable for a 5E3 given the wattage rating.


Heard the Tone Tubby alnico red 12 is supposed to be good but haven't seen any suppliers in the UK. Or the Celestion alnico blue more readily available in the UK.


Cheers,


David.

[mayburyds]

Think you are right about the tuning aspect.


My P/T is from TAD as part of their 5E3 kit, basically a Mojo kit as far as I know.


This is from their site -


NEW VERSION: GRAND STACK: supports 6L6GC and GZ34/5AR4 tubes also!
Primary:   #70005
0 V   Black
230 V   White
240 V   Grey
Secondary:
340 V@ 0,15A   Red
0 V   Grn/Yel
340 V   Red
0 V Yellow
5 V@2A   Yellow
6,3V@3A   Green
0 V Green
With a 5Y3 (RT503) and idling current You get about 350V DC of B+, with a GZ34 (RT501) it is about 390V


The O/T is from TAD as well -


2x 6V6GT , aprox. 18 Watt with 4, 8 and 16 Ohms
traditionally made with authentic material, paper bobbin. exactly made after original specs for the 1957-1959 Fender 5E3 Deluxe amp but with additional 4 + 16 Ohms tabs to allow proper connecting to alternative speaker set-up and various external cabinets.

Primary:   
A1   Blue
B+   Red
A2   Brown


Secondary:   
16 Ohms   Orange
8 Ohms   Green
4 Ohms   Yellow
0 Ohm   Black

Valves that came with the kit -

V1 :12AY7/6072A TAD Premium Selected
V2 : 12AX7A/ECC83 TAD Premium Selected - V3/4 : 6V6GT-STR TAD PREMIUM Matched - V5 : 5Y3GT / 6087

In the amp at the mo - V1 is a Philips 5751 - V2 the TAD EEC83 - V3/4 matched Tungsol-6V6GT RI - V5 NOS GE 5Y3WGTB

UK power is around 240v 50hz.

My meter is a bog standard affair I got from Maplins (Radio Shack?)

Cheers,
David.

[mayburyds]

drgonzonm,


Thanks for your input.


Managed to tracked down copies of the books you've suggested.


Cheers.

[mayburyds]

Hi,


Just to close off this posting - got the Basic Audio manuals which look like interesting reading and will take me sometime to absorb and understand the information.


Installed a Texas Heat speaker to sort out the top end.


Well the speaker swap certainly helped with the top end but the bottom was far too much causing lots of rattles and vibrations.


Then I remembered that when I first built the amp it was sitting on a concrete floor and it sounded great. Now it is, or was, sitting on a wooden floor with a void under!


Had some 3/4" multiply, screwed some nylon cups to the bottom of the multiply and used that to decouple the amp and speaker cabinet from the wooden floor. No more boom and for some reason the controls seem more responsive.


Amazed at what a difference decoupling made.


Anyway, thanks again for your help.


Till the next time!


Cheers,


David.