First Build troubles - 5E3 w/ Voltages & pics!!!

[Wittgenstein]

Hello again,

I have made some progress since my first post (here w/ pics). I had wired the 12AX7 & 12AY7 backwards. My amp is still not well however. When I turn the volume knobs and the tone knobs, it cracks and makes a popping noise, occasionally cutting out. I have a decent amount of hum as well, but I think this is a star grounding issue as when I press on it with chopsticks it makes it much worse. Here are my pin outs (I am new at this, but I think I did it correctly):

V1 (12AY7)
Pin 1: -1.2v DC
Pin 2: -0.44v DC
Pin 3: 1.1v AC / 0.425v DC
Pin 4: 3.31v AC
Pin 5: 3.31v AC
Pin 6: -1.2v DC
Pin 7: -0.35v DC
Pin 8: 4.2v AC
Pin 9: 4.7v AC

V2 (12AX7)
Pin 1: -1.2v DC
Pin 2: -0.62v DC
Pin 3: 4.4v AC
Pin 4: 3.31v AC
Pin 5: 3.31v AC
Pin 6: -1.2v DC
Pin 7: -0.6v DC
Pin 8: 4.7v AC
Pin 9: 3.4v AC

V3 (6v6GT)
Pin 1: 3.3v AC
Pin 2: 3.3v AC
Pin 3: 0.3v AC
Pin 4: -0.98v DC
Pin 5: -0.33v DC
Pin 6: -0.33v DC
Pin 7: 3.3v AC
Pin 8: 0v

V4 (6v6GT)
Pin 1: 3.88v AC
Pin 2: 3.3v AC
Pin 3: -3v AC / -1.08v DC
Pin 4: -1.1v DC
Pin 5: -0.26v DC
Pin 6: 3.33v AC / -0.26v DC
Pin 7: 3.33v AC
Pin 8: 0v

V5 (5Y3GT)
Pin 1: 9v AC / 0.25v DC
Pin 2: 3v AC / 417v DC
Pin 3: 8.1v AC / .63v DC
Pin 4: 382v AC / .4v DC
Pin 5: 5.75v AC / .4v DC
Pin 6: 382v AC / -3.5v DC
Pin 7:2.85v AC
Pin 8: 6.7v AC / 417v DC

Does this look alright? What is proper values for a 5E3. I have found layouts for the 5F1 Champ that include voltages at different stages; Is there a similar layout anyone knows of for the Deluxe?

Thanks again,
Wittgenstein (David)

[martin manning]

Pins 3 and 4 on the 6V6's should have something close to the HT voltage, with pin 4 being a little lower. The 5Y3 is putting out 417V, but it's not getting to the output tubes or anywhere else. Something is not connected between the rectifier and the B+ rail... it's like the amp is on standby.

[Wittgenstein]

Lol... that might be because it was on standby. I will repost again with the standby off.

I did make progress today thanks to loudthuds suggestion. One again I was an idiot and had switched the two blue wires going to the 12AY7 that run under the board when I had to redo that socket. I was able to use a multimeter to check the Ohms between the turrett and the pin to determine they were switched. Now I am able to play without oscillation or popping sounds, but for some reason the two bright channels are not working. It plays fine, asside from hum on the 2 normal channels. After poking around with chopsticks on the inside, I think I have narrowed the some of the hum down to the star ground and the 1M resitors on the input jacks. I would really like to quite it down. I am almost there thanks to all the help I have recieved here.

[martin manning]

FWIW, lead dress is often a source of unwanted hum. Looking at your photos, I think you have a lot of extra wire in there. You want it to look more like the attached pic (not mine; someone else showing off a nice, neat job on some other forum). I would also reinstall the power cord and strain relief. You should have 3/4-inch or so of the outer covering extending through the strain relief to the inside of the chassis.

[Wittgenstein]

Voltages w/ Standby Off

5Y3
1- 3.61VAC
2- 413VDC
4- 366VAC
6- 368VAC
8- 412VDC

6V6's
2- 3.28VAC
3- 402VDC
4- 370VDC
8- 23.83VDC

12AX7
1- 180.1VDC
3- 1.46VDC
4,5,& 9- 3.26VAC
6- 221.4VDC
7- 18.5VDC
8- 51.4VDC

12AY7
1- 133.1VDC
3- 2.2VDC
4, 5, & 9- 3.26VAC
6- 135.7VDC
8- 2.2VDC

[tubeswell]

5Y3
1- 3.61VAC
2- 413VDC
4- 366VAC
6- 368VAC
8- 412VDC

IMHO, 5E3s runn better with a B+ voltage around 340-360. You gave a bit over 400 - a bit on the high side for a stock 5E3, but not out of the ordinary, depending on how the output tubes are biased.

6V6's
2- 3.28VAC
3- 402VDC
4- 370VDC
8- 23.83VDC

What value cathode resistor are you running? If you have a standard 250R, your cathode resistor is passing (23.83/250 =) 95.3mA, which, with a plate to cathode voltage of 378, is a tube dissipation of 18W per tube. You should get it down to 12W if you are running 6V6GTs or 14W if you are running 6V6GTAs or JJ6V6Ss (although I think the JJs could probably even run alright at 18W - or at least 16W)

12AX7
1- 180.1VDC
3- 1.46VDC
4,5,& 9- 3.26VAC
6- 221.4VDC
7- 18.5VDC
8- 51.4VDC

Generally not out of the ordinary for a 12AX7, but the only questionmark I have is pin 7. If you have a properly-biased cathodyne stage, then the grid voltage should be just a couple of volts or so below the cathode voltage (on Pin 8). Are you sure you have wired this stage correctly? If you think you have, then maybe go back and check your resistor values. In a stock 5E3, the 1M grid load resistor for the cathodyne stage should go to the junction of the 1k5 and the 56k cathode resistor.

12AY7
1- 133.1VDC
3- 2.2VDC
4, 5, & 9- 3.26VAC
6- 135.7VDC
8- 2.2VDC

Nothing out of the ordinary

[martin manning]

Generally not out of the ordinary for a 12AX7, but the only questionmark I have is pin 7. If you have a properly-biased cathodyne stage, then the grid voltage should be just a couple of volts or so below the cathode voltage (on Pin 8).

True, but the meter is probably causing a false reading by giving the grid a reference to ground. Since the voltages on pins 6 and 8 look reasonable, I'll bet it's fine as it is.

Wittgenstein, it would be helpful to know the last B+ string voltage, at the positive end of the third 16uF filter capacitor. Are you using the original 5E3 schematic and component values? (edit: I see... Triode layout) This info will help complete the picture. If you measure the string voltages, post the values at all three filter caps so we can see if the first two have drifted due to line voltage variation.

How does it sound now?

[Wittgenstein]

5E3 build (attempt 2) still not working but coming along

To consolidate and clean up my threads a bit, I will continue to use only this thread for all future troubleshooting of my 5E3 build. I have included links and descriptions to all my previous post to provide more information and history. I really appreciate all the help and wisdom that I have received so far, and I feel that I am close to nailing this grounding issue.

http://music-electronics-forum.com/t21284/
First post - Just built my amp for the first time with little idea what I was doing.
Problem: No sound from input just hum
Solution: (figured out I had the 9 pin connections reversed) still hummed though.

http://music-electronics-forum.com/t21286/
Second post w/ pics of first build attempt
Problem: Pots behaving strangely & lots of hum
Solution: None, troubleshooting continued to the next post.

http://music-electronics-forum.com/t21376/
Third post w/ pin voltages (thread #5)
Problem: Pots behaving strangely & lots of hum
Solution: None, voltages measured

http://music-electronics-forum.com/t24149/
Forth post w/ pics of second build attempt - My most recent attempt at this kit, which involved taking everything back out of the chassis and a complete re-wire to clean up lead dress.
Problem: Hum worse after rebuild, and abandoning one star grounding scheme.
Solution: Work in progress, pictures and B+ voltages added below (advice welcome)

[Wittgenstein]

How does it sound now?

I re-wired the hole chassis to clean up the lead dress and shorten whatever wires I could. I tried as much as possible to wrap any exposed leads in heat shrink to further eliminate any hum, but in the end it sounded worse then it did before. I'm sure this is because of my changes to the ground scheme. Triode uses a one star grounding scheme that, after research I think is very poor, especially with uninsulated jacks. I thought on this build I could avoid some of the long ground wires running back to the only star ground, but in doing so I'm pretty sure I just made the grounding worse. I re-read the aikins star grounding literature and last night for the first time it finally clicked in my head.

Soo... here are some gut shot pictures of my second soldering attempt.

[Wittgenstein]

First build attempt

I think it is tidier then my first go (see attachment), and I know that many of the wires are much shorter.

[tubeswell]

I think it is tidier then my first go (see attachment), and I know that many of the wires are much shorter.

Hi Wittgenstein, that is a lot tidier. See how you have that black covered wire between the ground of the pre-amp filter cap and the screen node filter cap? That is the wire I would remove, and I would run a separate wire from that pre-amp filter cap ground return to the input jack (sleeve) ground lug, and have all the other pre-amp ground returns, each going by their own separate wires, to that same input jack ground lug.

Keep the ground return from the screen node filter cap grounded with the return from the reservoir filter cap (together with the 6V6 cathode resistor ground return and the 6V6 220k grid resistor ground returns, and the HT winding centre tap)

[Wittgenstein]

New grounding idea

I realized last night after reading more on grounding and looking at the Tridoe layout grounding scheme that I have it all wrong. I think the original layout is bad in and of itself, but with my changes it just compounded the problems. First off, the pre-amp cathode ground (V1) has a black wire running on the underside of the board daisy chaining it back through the PI stage to the second 16uf filter capacitor which then runs with a wire back to the first filter cap and HT center tap. That is not great but didn't give me too much trouble when everything ran back via its own ground wire back to that same star ground. I did not like this design for I thought it created unneeded long ground wires running all over. I was correct in my assumption, but I did not understand how to properly implement it. Namely, I have about 3 inches of separation from where the HT center taps make a ground to chassis, and where the first and second filter caps ground into their own chassis lug. So not only is the power stage coupled with the PI and pre-amp stage, but to make it worse, it does not even tie back into the the main star ground.

I plan on using a 3 star grounding system, and I already ordered fiber washers to go with my plastic shoulder washers for insulted switchtcraft jacks. The first star ground point will be located on the bolt of the power transformer and will contain the HT center taps, output transformer secondaries common, and the first 16uf filter cap ground. The second star ground point will be about further up the amp attached to the output transformers bolt, which conveniently happens to be located right by the ground of the second 16uf filter cap ground. This second star point will contain just the phase inverter (PI) stage's (12ax7) grounds. Finally I plan on placing the third star ground point at the far opposite end of the chassis from the power cord's ground (technically the 4th ground point, but only the third green power cord wire runs here). It will be located as near as possible to the cathode ground of the 12ay7 or pre-amp section. It will contain the pre-amp sections ground, input jacks, and volume grounds. They should all then feed back down the amp into higher voltage grounds, but not the other way.

Any thoughts on this idea. I will add attachments of the layout diagram revised with my new idea to make it easier, as well as a layout of what I currently have going on. Please excuse my numerous and short post, as I work for an online website during the days when I post, and I only have so much time to slack off.. =).


Attachment 1 is current way I have it wired. Attachment 2 is my proposed grounding plan. In the second attachment I will be isolating all jacks from chassis. Does this look alright? Would I be better off only having 2 star grounds, by tying the PI section into the pre-amp & input jacks section, or is there a better way in general?

[tubeswell]

further to my PM

[Wittgenstein]

further to my PM

So like this? If you notice, I removed all the black grounding wires that run on the underside of the board. I also removed the small black wires on the negative side of the filter caps and 6v6 cathode cap, giving them all their own ground wire. I did wire the OT transformer secondaries common to a input jack lug and from their back to the main star ground. If figure I can cut this out later, to have it ground at the jack if it is a problem. All other grounds "red in your diagram" run back to the second star ground on the far side of the chassis (near the 12ay7) cathode cap and input jacks which will all be insulated. The one spot where I could not run a separate "red" ground back to the star was where the 56K resistor ties into the same turret lug with the third 16uf cap. I would think this would not matter too much, and should be a huge improvement either way.

I noticed that Hoffman lays out their board more like what you are saying. They even include the last 16uf cap further t0 the right on the board, near the PI and pre-amp circuits. I think I prefer this layout much better and seems easier to follow when looking at the schematic. + line is obvious and easy to measure once build. It is also easy to see how they split the grounds into two sections. Power and output into one ground, pre-amps, PI, and EQ into another with the jacks and pots. Do you have any thoughts on this.

As it stands now... my amp will not make any noise. I'm not sure what is wrong as I have ohmed out every pin and connection and everything looks fine. When I flip the standby switch, I hear a slight noise that fades quickly, much like the noise of turning off a tube television after it has been running for awhile. I double and triple checked all the connections. It really has me stumped. If I have to rip the board back out again, I am considering testing and reusing most of the passive parts, but on a new turret board in the Hoffman style.

[tubeswell]

yep. The only other thing possibly is to try it with the 220k grid leak resistors grounded with the Output stage, but then swap them to the pre-amp, if the first way is hummier.