5E3 Proluxe problems

[passfan]

Hi all. I just finished wiring up this amp today and I noticed a couple of problems. I used the shorting jack plugs on the inputs and wired them according to the diagram and they work great other than the contact point on the ground doesn't make contact when a jack is unplugged. Buzzes like crazy and I can't get them bent back right so they make contact. Clipped them together and continued on to problem two when I'm not playing I get a slight buzz but as soon as I play it quiets completely, I mean gone, nada, zip... but as soon as I stop it comes right back. It's not like I can't hear it under what I'm playing it's like someone used a noise gate on it and took it right out. When I stop playing there's a lag of a second or so before it starts buzzing again. I might add it only does this when volume 2 is up also. If volume 2 is down it has a continuous buzz. Anyone ever hear anything like this? Other than that this amp is a beast, I love it.

[passfan]

For those wondering, I found a mistake. It seems upon tearing out the extra jacks at the input in favor of a single jack, I discovered the 1 meg resistors were tied to the shorting pin instead of ground. This would account for the buzzing everytime I plugged in. My input was losing it's ground reference. I have also lifted my heater supply with a couple of 100 ohm resistors so we'll see later on today. It should quiet down a bit.

[passfan]

Well that's not it. What ever it is it's in the preamp. The 68K resistors are super sensitive as was the wires coming off them. I could touch them with a pencil and set the whole amp off. I substituted a 1k resistor in place of the 820 ohm bias resistor, could this be driving this problem?

[steve25]

The only resistor you need is the 1 meg to ground from the grid/input.
The 68k or whatever resistor is used to block interferance such as picking up a strong local radio signal, and the 68k resisitors together give the #2 input half the gain of the # 1 input.
On my builds at the grid I started using a 33k resistor and a small frerite bead to block RF.

[ziess]

Do you have any pics of your input wiring?

[passfan]

I'll check out the smaller grid resistors. Sadly I have started tearing it apart in search of the buzz as well as to change some components out on the board. I used Mallory 150's and they're acting microphonic and I discovered the plate resistors I used are only rated for 300 working volts. I need to change them.

[ziess]

I take it it's fair to presume you tried different tubes?

[passfan]

A half a dozen, 12ax7's, 7025's, 12at7's. Went from cloth wire to shielded, went from 1k bias resistor to 750 ohms. Always a 60hz hum with a 120 hz which responds to volume. I have an AC star ground with a separate signal star ground tied to the chassis, heater supply is lifted. It sounds really sweet, I just can't play it with that buzz. I guess when I get it put back together I'll clip up a 220pf cap and start looking for the source. Is it normal for the preamp section of a tube amp to be so touch sensitive ?

[ziess]

Are your input jacks isolated from the chassis properly?
The first stage is always sensitive, but it shouldn't be as bad as you're describing.
It sounds like a grounding problem, to be honest. I've never felt the need to implement a star ground in a Fender-style amp, I've always thought them to be overkill but some guys like them I suppose. You might try redoing your grounds to match the original 5E3 schematic.

Any pictures?

Tommy.

[rudutch]

6L6 or 6V6?

[NTBluesGuitar]

If you have your filter grounds on the star along with the grounds from the preamp stages, you're going to have a ground loop. You'll either need to isolate the jacks or move the filter grounds off the same point as the preamp, to a dedicated point (I use the lower right lug of the PT). I recommend using star washers with the input jacks for ground reference; no need to wire a dedicated ground from them this way.

As Tommy mentioned, in tweeds, following the brass plate grounding scheme/points yields great results. I've done this Proluxe build for someone once using the standard ground scheme and it's very quiet:

[CzarSketch]

well now we're all just drooling at that amp porn. I know it's been said before, perhaps about this exact same photo, but NT, you are gifted.

[NTBluesGuitar]

Wow...thanks!

This was a 'rescue job' in which the owner got started and then ran out of time and realized it was too much to figure out in the little amount of time he had to work on this. I basically just did the wiring inside. The rest was already pre-assembled.

To be fair, I do have a long history with art/illustration and design, so my hands and eyes are pretty well-trained; it lends itself to this kind of work!

Back to the OP's topic, note in the first pictures the star-washer grounded input jacks on the brass plate, no need for dedicated lug-to-plate wires.

[rudutch]

when I converted mine to 6L6's, I ... er... uh...

well, if you "miss" the 2 - 100 ohm resistors from pins 2 & 7 on the output tubes.. you get

HMMMM

[passfan]

Wow...thanks!

This was a 'rescue job' in which the owner got started and then ran out of time and realized it was too much to figure out in the little amount of time he had to work on this. I basically just did the wiring inside. The rest was already pre-assembled.

To be fair, I do have a long history with art/illustration and design, so my hands and eyes are pretty well-trained; it lends itself to this kind of work!

Back to the OP's topic, note in the first pictures the star-washer grounded input jacks on the brass plate, no need for dedicated lug-to-plate wires.

After reading your posts on grounding I realize my issue. I have a ground loop on top of my other issues. I also used an aftermarket chassis with no brass grounding plate. I am going to spring for a chassis and ground plate and rebuild everything into that. I really love the control I have with this amp. Do I see your cathodes from the preamp soldered to the brass plate as well ? I will post pics from the rebuild as my chassis is pretty much in the torn down stage now. Thanks all for the help , I'll resurrect this thread in a couple weeks.

[NTBluesGuitar]

That's right...everything went to the brass plate except the CT leads from the power transformer.

You can do a star or buss ground, but the trick is to move the filter grounds well away from the preamps and star-washer-ground the inputs (or isolate them from the chassis).

[passfan]

That's right...everything went to the brass plate except the CT leads from the power transformer.

You can do a star or buss ground, but the trick is to move the filter grounds well away from the preamps and star-washer-ground the inputs (or isolate them from the chassis).

So you tie the filter grounds to the brass plate , just well away from the preamp grounds. Does the plate tie to anything ? Sorry to pick your brain but after hearing this amp I have to have it. Ordered a chassis from Uncle Ned in Chicago earlier. Thanks

[ziess]

The original 5E3 layout is really the simplest thing in the world.

http://www.recproaudio.com/diy_pro_a...5e3_layout.gif

The -Ve end of all the caps ground onto the plate where they meet it, the jacks just screw right on and don't require a soldered ground and the pots are grounded through their bodies.
The plate is sandwiched against the chassis by the pots and jacks and grounds through contact alone. Put a bit of solder on the plate where you will be putting ground wires before you install it as it's hard to get at later (you can solder the wires to the plate outwith the chassis and solder to the board post-installation if you think it'll be easier). You'll need a decent powerful (80W or so) iron for the plate.
I really do think the simplest way is the best way to do these amps, they really were done right the first time round.

Tommy.

[passfan]

The original 5E3 layout is really the simplest thing in the world.

http://www.recproaudio.com/diy_pro_a...5e3_layout.gif

The -Ve end of all the caps ground onto the plate where they meet it, the jacks just screw right on and don't require a soldered ground and the pots are grounded through their bodies.
The plate is sandwiched against the chassis by the pots and jacks and grounds through contact alone. Put a bit of solder on the plate where you will be putting ground wires before you install it as it's hard to get at later (you can solder the wires to the plate outwith the chassis and solder to the board post-installation if you think it'll be easier). You'll need a decent powerful (80W or so) iron for the plate.
I really do think the simplest way is the best way to do these amps, they really were done right the first time round.

Tommy.

I guarantee it's better than my way. Thanks for the help Ziess.

[ziess]

No problem, happy to help. I've done quite a few tweeds so feel free to email me if you need any more advice.
What are you using for the transformers and speaker?

Tommy.

[passfan]

No problem, happy to help. I've done quite a few tweeds so feel free to email me if you need any more advice.
What are you using for the transformers and speaker?

Tommy.

My power tranny is from Weber my ouput is from here http://www.musicalpowersupplies.com/3.html
It's the OT40PP Supposed to be the one Richter is using.

Speaker is a 10" Eminence Legend which sounded great right out of the box hooked up to my 20 watt SE from the AX84 site. I can't wait to break it in good.

[passfan]

Well I got it back together and it's a lot quieter. I still have an off again on again issue with an input jack but I rocked it hard for about 3 hrs tonight and it kicked butt. I got it back home and opened it up and my bypass cap on the output tubes went pop??? I noticed while I was playing my tubes had a blue glow but when I checked my bias voltage beforehand is was around 15.5 volts with a 300 ohm resistor. How could 15 volts pop a hundred volt cap?

[NTBluesGuitar]

It could pop it if it was wired with the polarity wrong. It's easy to do.

[passfan]

It could pop it if it was wired with the polarity wrong. It's easy to do.

Wow... I can't believe I installed it that way and when I found it last night , looked right at it , and still didn't see it. It's strange when I wired it the first time I was getting 412 volts on the B+ and this time I'm getting 360 volts. Even still when I max the volume I get a buzz ; not loud but annoying . I will post some shots later.

[passfan]

Well my B+ is back up to 391 volts , down to 369 volts at the next filter and down to 274 volts at the last stage. At the input tube it's down to 117 volts ??? is this right ? Yesterday when I checked bias it was at 15.5 volts for a 300 ohm resistor which would be 51 ma. Today it's at 26.6 volts for a 250 ohm resistor for a 102 ma. Since I have two output tubes I divide this number by two right. If that's right then holy cow... I had it so cold biased the first time no wonder my tubes had a blue halo to them.

Everytime I try to get loud the cabinet is rattling the chassis and it makes a noise that sounds like carton full of empty coke bottles clanging around (for those here who are old enough to remember that sound). Last night when I had it in the studio I plugged a 4-12 Marshall cabinet into it and sat it next to it and the noise disappeared. Has anyone else experienced this ?

[passfan]

Here is some amp porn for those who like to look.
http://i705.photobucket.com/albums/w...o/DSC03628.jpg

http://i705.photobucket.com/albums/w...o/DSC03627.jpg

http://i705.photobucket.com/albums/w...o/DSC03626.jpg

http://i705.photobucket.com/albums/w...o/DSC03629.jpg

http://i705.photobucket.com/albums/w...o/DSC03630.jpg

http://i705.photobucket.com/albums/w...o/DSC03631.jpg

[Don]

These amps can be a bugger to get all the rattles out of.

Tweaking the location of the chassis in the cabinet helps.

I also put strips of 1/4" wide foam backed tape on my back cover just where it contacts the chassis. It worked wonderfully.

It sounds more like you have a microphonic tube or two. Tap on them with a pencil eraser while the amp is turned on and cranked up.

[NTBluesGuitar]

Tidy wiring! Nice work. And I see that you did wire the cathode bypass caps backwards in the preamp. Can't see if you did the same with the power tubes' cathode bias cap.

And the grillcloth is going the 'wrong way'. Of course, that's all in the eye of the beholder.

Still...it looks pretty good! If you could get more shots like the second one of different sections of the amp, I could possibly help more with the other issues.

*edit* Don's point about the tubes is a good one. If you have any, try the amp with another set of tubes to see if the issues are recreated.

[Don]

Very nice looking amp!

Ampeg mounts the grill cloth on the Jet II amp that way. I like it. It differentiates it from a Fender.

[passfan]

Thanks guys, I've swapped out different sets of tubes to no avail. The output tube cap is the one that cooked. I didn't even notice the preamp caps in backwards, thanks NT. As I repair the mistakes it keeps getting quieter. I will have to try the foam trick as well, right now I'm playing it through a 2-12 cabinet to isolate the chassis. I will post some more pics later on, thanks.

[yankeerob]

I still have an off again on again issue with an input jack but I rocked it hard for about 3 hrs tonight and it kicked butt.

We've had a hell of a time with Switchcraft L11's - so much so that we're considering going to Cliff types - I have had - on another amp - not a 5E3 but it doesn't matter as we're talking about the input here - a situation where I could remove the screened wire from the Switchcraft jack and inject a 1Khz straight down the wire into the first triode and the amp worked fine - reconnect it to the jack and the damned thing just buzzed like mad - filed the plating off the terminals of a fresh jack, tinned it up real good, re-assembled and buzzzzzzz... took the wire back off and inject signal - no probs - figure that one out... especially as it's wired identical to two other siblings on the shelf that work fine...

BTW - if you use a 68K grid stopper in series to your input to the first triode on a 5E3 and loop a 10K from that to the second you have a very simple way of linking both 'channels' with a single input that works a treat. Don't worry about losing any input gain - it makes so little difference it's not worth worrying about and will be happy as Larry with anything you stuff in front of it ie any pedals with a boisterous output...

Hope you get it going steady