First 5E3 - Distortion,

[EllArr]

Sorry about the long post, guys. I'll try to be less verbose in the future. Been lurking and reading for about 8-9 months and have built one single - ended amp called the Sonic MA-1 from one of Tino Zottola's books. I like this little amp a lot, and building it gave me the courage to accumulate the parts and tools and build a push-pull design. I have always wanted to have a 5E3 Deluxe, because I like the sound and its design and I are about the same age.

The amp sounds OK cranked, with the expected breakup but a hint of "ring modulator" - type sound when strumming the guitar quietly. It remains distorted at whatever volume I play at, and the distortion sounds to my relatively untrained ear like the starved plate distortion from one of those Digitech pedals that uses a 12AX7 to produce what they call their "tube warmth" effect. There is no position on either of the channels that gives anything approaching a clean tone.

Maybe I should mention that this amp is much better about hum than I expected it to be. I've heard lots of Deluxes and other tube amps, and this is as quiet as the best of them.

I've read a lot of posts from folks who are having similar problems, and am reluctant to try everything all at once, so what I've done first is to swap out the 12AX7 preamp tube with a 12AY7. Not much change, just a slight loss of volume. Then I reviewed the build according to Triode Electronics' layout PDF file. (Many thanks to whoever posted that; it made things very clear.) I found some discrepancies on the PI tube's wiring, so I rewired to match what I saw on the Triode layout. Checked voltages, and they followed the wires to their new positions. There is little, if any, discernible change in the sound of the amp.

Here are voltages:
5Y3GT:
Pin 2 - 385DC, AC should read 5V but fluctuates wildly
Pin 4 - 352AC
Pin 6 - 352AC
Pin 8 - 384.5DC, AC should read 5V but fluctuates wildly

6V6 #1:
Pin 2: 3.22AC
Pin 3: 370DC
Pin 4: 347DC
Pin 7: 3.22AC
Pin 8: 21.5DC

6V6 #2:
Pin 2: 3.22AC
Pin 3: 370DC
Pin 4: 347DC
Pin 7: 3.22AC
Pin 8: 21.5DC

12AX7 PI:
Pin 1: 120DC
Pin 2: 0, should be 25
Pin 3: 1.5, should be 55
Pin 4: 3.21AC
Pin 5: 3.21AC
Pin 6: 267DC, should be 140
Pin 7: 230DC, should be 0
Pin 8: 244DC, should be 1.5
Pin 9: 3.21AC

12AY7 Preamp:
Pin 1: 132DC
Pin 2: 0, should be 25DC
Pin 3: 2.1DC, should be 1.5DC
Pin 4: 3.18AC
Pin 5: 3.18AC
Pin 6: 142DC, should be 135
Pin 7: 0
Pin 8: 2.1DC, should be 1.5
Pin 9: 3.18AC

Something is seriously wrong in the phase splitter, but I am too much of a rank n00b to understand how to fix it. Any help would be appreciated.

If it would help to give it a listen, I can record a sample or two and upload them.

-Lennie

[Steve Conner]

It's strange that you have those "fluctuates wildly" readings. Pins 2 and 8 of the 5Y3 are supposed to be relatively smooth DC with only a little AC ripple. (Try turning your meter's autoranging off, if it has that feature.)

Also, a lot of ripple would explain the ring modulator tone that you mentioned.

I suggest checking your filter capacitors (the 16uF, 450V ones) and making sure they're properly wired and in good working order.

As for the PI voltage readings, most voltmeters will load down the PI grid voltage and give a false result. But it would take something like an old analog Simpson to load it all the way down to 0, and no meter would make the voltages higher than they should be.

So, on account of the weird voltages, double check that you used the correct resistors in the PI. Those colour bands are easy to get mixed up.

Sound samples are always welcome. The 5E3 should get loud enough to drive your neighbours crazy before it starts to distort.

[Chuck H]

Those voltages are so cattywhompus that I'm surprised it's working at all. There are definitely some miswire and possibly component value problems going on. If you like the amp now you should love it when it's wired correctly.

How about some gut shots? As clear as possible so we can see the color codes on the resistors if possible. Don't worry about showing your work, really. We've seen it all.

[loudthud]

A common mistake in a 5E3 is swapping pins 7 and 8 of the 12AX7, the phase inverter. Bruce says the amp will make about 2 watts. Link: http://music-electronics-forum.com/t24269/

[EllArr]

It's strange that you have those "fluctuates wildly" readings. Pins 2 and 8 of the 5Y3 are supposed to be relatively smooth DC with only a little AC ripple. (Try turning your meter's autoranging off, if it has that feature.)

Also, a lot of ripple would explain the ring modulator tone that you mentioned.

My meter is an Extech 430. I am able to turn off autoranging, and when I do, I get the following:

Pin 2: 9.7AC
Pin 4:
Pin 6:
Pin 8: 7.7 AC

Could these voltages damage the rectifier's heaters, or be an indication that they're bad?

I suggest checking your filter capacitors (the 16uF, 450V ones) and making sure they're properly wired and in good working order.

Yeah, I'm going to have a look at them later this evening.

As for the PI voltage readings, most voltmeters will load down the PI grid voltage and give a false result. But it would take something like an old analog Simpson to load it all the way down to 0, and no meter would make the voltages higher than they should be. So, on account of the weird voltages, double check that you used the correct resistors in the PI. Those colour bands are easy to get mixed up.

I will look at those as well. Thanks for your reply.

Sound samples are always welcome. The 5E3 should get loud enough to drive your neighbours crazy before it starts to distort.

My neighbors are already a bunch of wild-assed Hondurans. They play their tejana music so loud they can't hear anything.

[Chuck H]

My neighbors are already a bunch of wild-assed Hondurans. They play their tejana music so loud they can't hear anything.

Bonus

[EllArr]

Bonus

Yeah, they're good folks, and they know how to party.

Getting back to the issue at hand: I'm pretty sure that the resistors across the + end of my filter caps are at fault here, and am going to swap them out. I went ahead and ordered new caps just to be on the safe side. If it turns out I don't need them, I can use them in another build, or keep them on hand for spares.

I like this forum. I'm used to belonging to boards where knives and pistols get drawn frequently, and people are comparatively very nice around here, even when they disagree.

[Bruce / Mission Amps]

All the voltages look OK to me except the phase inverter triode.
Your phase inverter triode is messed up. Could be the wiring as Loudthud suggested, or the actual parts you used are wrong bad... etc.
I don't know how you have the socket wired and I have noticed that some builders mount their tube sockets in the chassis 180 degrees rotated so you have to look there yourself.
12AX7,
If wired so section B of the dual triode is the phase inverter:
lug #6 should be around 200vdc, lug #7 should be around 25vdc-45vdc (this one is hard to read with a cheap meter) and lug #8 should be around 40vdc to 55vdc.
The high cathode voltage suggest a bad tube, short on the socket, miswired or the phase inverter cathodes resistors aren't grounded.

Section A of the dual triode
lug #1 should be around 160vdc to 180vdc, lug #2 zero volts DC, lug #3 about 1.2vdc to 1.6vdc.

[EllArr]

Here are a few gut shots. I'm still getting the same distortion, but now have killed the first set of inputs. These are 14.1 megapixel images. I hope they show enough detail.

http://ellarr.com/Deluxe5E3/P3192715.jpg
http://ellarr.com/Deluxe5E3/P3192717.jpg
http://ellarr.com/Deluxe5E3/P3192718.jpg

If anyone needs to see it from another angle, please let me know. I appreciate it, folks.

[Bruce / Mission Amps]

This is why I use color coded wires with my kits... so when working with my novice builders and their pictures, I can clearly see where the red wires, yellow wires, yellow/black wires and blues are supposed to be going to, with respect to their real work and the supplied layout!

What is going on with:
that insulated wire from the common point of the power tube's 220K grid load resistors?
How the 1500 ohm grid stopper resistors on the power tube sockets are wired and mounted?
The plate load resistors of the 12AY7 socket, lugs 1 and 6 with respect to lugs 2 and 7 and the proper Mic and instrument input jacks?
Lugs 6,7 and 8 of the 12AX7 socket and their supporting resistors, etc.

[EllArr]

This is why I use color coded wires with my kits... so when working with my novice builders and their pictures, I can clearly see where the red wires, yellow wires, yellow/black wires and blues are supposed to be going to, with respect to their real work and the supplied layout!

What is going on with:
that insulated wire from the common point of the power tube's 220K grid load resistors?
How the 1500 ohm grid stopper resistors on the power tube sockets are wired and mounted?
The plate load resistors of the 12AY7 socket, lugs 1 and 6 with respect to lugs 2 and 7 and the proper Mic and instrument input jacks?
Lugs 6,7 and 8 of the 12AX7 socket and their supporting resistors, etc.

Result!!

It was the grid stoppers on the power tubes! I just got through playing through it for and hour, and it kicks ASS! It's exactly the tone and volume my band needs for practice here in my little studio. It is also surprisingly quiet when cranked - little hiss or hum - so I must have gotten the preamp stages right.

Since I started working on this thing, I've been out of work twice, been to Ireland, been to France, been back to Ireland, and have been busy looking for work. It has been in the back of my mind nagging nagging me, coming to me like a succubus in the night, and I've either been to busy or too tired to fool around with high voltage stuff. Finally, I blocked out this afternoon as a time when I would either do it justice or go bust on it. You folks have helped me get it straightened out. If I'd known I'd be this tickled about it, I'd have made time weeks ago.

Now, I have an old Filmosound that I've gutted and am going to start reassembling it with new caps and resistors. I can actually use a lot of this circuit to go by.

Thanks again, folks. I hope I can learn enough to make a contribution here.

BTW, Bruce, in future I'll color code my wires. I've learned my lesson from this one.