First Build, 5E3, strange problem, help please

[cfidave]

dai,

I think you hit the nail on the head. As a first time kit builder, I was simply copying a layout that came with the kit. When that did not work, I was clueless on how to fix it. I did not understand the theory behind what I was trying to do. Most of the grounding layouts I looked at were not specific enough for me follow correctly. A prime example of this is from the Hoffman site:
"Make sure all Jacks and pots are bolted down firmly to the metal chassis. If you use plastic jacks, make sure all jacks are grounded to the pot buss wire".

Since I used metal jacks, I simply did what the site said not knowing I was setting up a potential ground loop, by not grounding all jacks to the buss wire. I have learned a lot from this thread, thanks to all the advice. It would have been much better to have had at least a basic understanding, of what grounding is all about, before starting the build. Lesson Learned.

[hasserl]

Well let's be clear about two things my friend. This grounding scheme was not a Hoffman but an incomplete Hoffman. Big big difference. Secondly, a Hoffman grounding scheme is not a star ground scheme and Mr. Hoffman hates star ground schemes. you obviously need to do a little more research on the subject. And I'll say one more thing, I'll put my Hoffman layout and grounding scheme up against any brass plate Fender layout for quiet operation and kick The Fender's tail. I have a strange feeling you've never built a Hoffman layout/ground scheme amp. I've built 40 plus and every owner is amazed by how quiet they are. You should give it a try. No offense intended, just telling it like it is.

I never said the Hoffman ground system was a star ground, you read that into what I wrote. You're right that I've never used the Hoffman ground, I've never even checked into it or know the layout is. What I do know is there have been several threads over the years here with people grounding their amps with what they picked up off the Hoffman website and they've had noise issues. Whether they followed the layout correctly or not I really don't know or care.

Like I said, it's a simple circuit and it works fine just as Leo did it. There's no need to reinvent the wheel, IMO. If you just layout it out like a Fender and use the brass grounding plate you won't have ground related noise problems. Simple circuit, simple layout, don't complicate something that doesn't need to be complicated. Save your time and creativity for something that will make a real difference.

[bnwitt]

I never said the Hoffman ground system was a star ground, you read that into what I wrote.

Maybe not but you insinuated that it was like a star ground in the fact that it too had noise complaints associated with it.

You're right that I've never used the Hoffman ground, I've never even checked into it or know the layout is.

And yet you completely dismiss its potential improvement in noise floor reduction over the standard Fender 5E3 layout.

Whether they followed the layout correctly or not I really don't know or care.

Not interested in factual comparisons I guess.

Like I said, it's a simple circuit and it works fine just as Leo did it. There's no need to reinvent the wheel, IMO. If you just layout it out like a Fender and use the brass grounding plate you won't have ground related noise problems. Simple circuit, simple layout, don't complicate something that doesn't need to be complicated. Save your time and creativity for something that will make a real difference.

Well my experience is somewhat different. I have had my hands on numerous original Fender deluxe and other tweed era amplifiers and they all have had some amount of hum present at zero signal. I have also built at least 9 or 10 5E3's with the Fender layout and the brass plate grounding and they too had some hum at zero signal. Once I tried the Hoffman layout on my first 5E3 there was no turning back. Now I will admit that I have added a few changes to the current Hoffman scheme like running a ground to each input jack and then wiring the whole preamp section to a chassis ground bolt, plus I never use a PT bolt for power section or center tap grounding. The result is a 5E3 with no hum at any volume level period. Sometimes a little tube hiss on full volume but that has nothing to do with grounding. I have had so many customers tell me that they thought some hum was just part of tube amp life and are really surprised that it doesn't have to be.


I really think you should try a Hoffman ground scheme before you summarily dismiss its value. Remember, it took a long time for folks to except that the world was round and not flat. Experimentation is a great thing. Saying the way its always been done is just fine prevents new discovery.

[hasserl]

Maybe not but you insinuated that it was like a star ground in the fact that it too had noise complaints associated with it.

Yes, in that people have come here looking for help with a noisy amp after having tried both of those schemes'.

And yet you completely dismiss its potential improvement in noise floor reduction over the standard Fender 5E3 layout.

Again, you're adding to what I said. I didn't completely (or summarily) dismiss it, I said this isn't the first time someone used the scheme then came here looking for help with noise, and I posted that the stock arrangement works fine and IMO is what a builder should use, in particular a new builder that will typically have plenty of other things to occupy their attention.

If you've built 40 5E3's, I don't blame you for moving past the stock layout, or circuit for that matter. But if it's your first amp, the smart thing is to stick to the tried and true circuit/layout. IMHO of course.

You seem rather defensive, no need to insult or assume things about me. Where are you at in Southern Cal? I'm local, in Orange Co, perhaps this would be better discussed over a beer.

[cminor9]

I'm local, in Orange Co, perhaps this would be better discussed over a beer.

Discussing religion (grounding schemes, same diff) over a beer?!? What, are you trying to start a barroom brawl?



I kid! I kid!

[cfidave]

I wanted to give a final update, and also thank those who took the time to try and help out.

After trying several grounding schemes, with no change in the problem, it became obvious that grounding was not the issue. I pulled the board and re-soldered any joint that looked less then stellar, also replaced most of the preamp components. Still no change. As a last resort I installed two new preamp sockets and was very carefull on the quality of my soldering on the preamp pins. Previously, they looked a little sloppy. The hum problem with guitar plugged in, is gone! Not sure if I had a bad sockett, or a cold solder joint, but the problem was in one or both of the preamp sockets.

The final grounding layout I used is the one Bruce Collins, from Mission Amps,
suggested. He was kind enough to spend considerable time on the phone with me, even though my 5e3 was not his kit. With this layout there is absolutely zero hum with no signal, and controls turned full up. Special thanks to him.

This is a great forum, and I am looking forward to contributing, as my knowledge grows.

[bnwitt]

You seem rather defensive, no need to insult or assume things about me. Where are you at in Southern Cal? I'm local, in Orange Co, perhaps this would be better discussed over a beer.

Now you're reading things into my posts. Really, I'm not being defensive nor did I intend to insult you. I just happen to be an extremely right brain matter of fact communicator and sometimes I am perceived to be less than cordial in forums as my face is not visible. I have built well over 40 5E3 amplifiers in the last 12 years and know the Fender and Hoffman layouts very well. I will say that the difference between the noise floors of the two amps is audible but both amp schemes can be pretty quiet. I am in the middle of no where out here in Temecula/Murrieta.

[bnwitt]

I wanted to give a final update, and also thank those who took the time to try and help out.
Not sure if I had a bad socket, or a cold solder joint, but the problem was in one or both of the preamp sockets.

I would almost guarantee it was a bad solder joint on one of the grid pins of V1 or V2 most likely V1. I have had this problem before. You can wrap your fist around the wire of the offending connection and reduce the hum when this is the problem.

The final grounding layout I used is the one Bruce Collins, from Mission Amps,
suggested. He was kind enough to spend considerable time on the phone with me, even though my 5e3 was not his kit. With this layout there is absolutely zero hum with no signal, and controls turned full up. Special thanks to him..

Bruce is one heck of a gentleman.