5e3 crackling and popping

[Tubed]

Just finished a 5e3 using Hoffman layout. It sounds great, but i am getting a crackling noise out of the speaker. I replaced all the tubes and
it did not help. I found that I have dc volts on all three lugs of the volume and tone pots, so I replaced the coupling caps and that did not work. Then I removed all the wires from the board to the volume and tone pots, and still that did not stop it. With my limited knowledge, it seems like the dc current is coming from the ground? I am using a Hoffman ground buss connecting the pots, jacks "isolated" and the preamp all bolted to the chassis. The pot housing, jacks and the ground bolt all have dc volts on them- "they are all connected together". Any help would be greatly appreciated.

[tubenit]

Try "chopsticking" the amp carefully to see if you find a solder joint that needs to be reflowed. If you're not sure what chopsticking is then do a "search" on the forum.

Also I'd try a different speaker. Make sure the speaker wire is good. Make sure the guitar cord to the amp is good.

Make sure the pots and the input jack are bolted down tightly enough to make good contact with the chassis.

With respect, Tubenit

[jojokeo]

What type of load resistors are you using? Carbon comp, metal film, etc.?
Are you using any old parts or is everything new in the build?

[Tubed]

I chopstick-ed every connection and went ahead and re-soldered many of the of the joints to no avail. Tried a different speaker and cable, checked the input jacks,pots and ground lugs for tightness still no change. Jojokeo, this amp has all new parts and i used metal film resistors. The amp works fine other than the crackling and it crackles without the guitar plugged in and I still get dc on the pots with all the tubes removed except the rectifier. What could cause dc to get on the pots and input? my other build is identical and work fine.
Thank you, Tubed

[plexi50]

Best thing to do is carefully one at a time verify all your under board connections (If Any) Plate resistors and coulping cap from V1 on down the line. It's easy to make a simple mistake even after years of doing this. Human error is my friend

[stingray_65]

Best thing to do is carefully one at a time verify all your under board connections (If Any) Plate resistors and coulping cap from V1 on down the line. It's easy to make a simple mistake even after years of doing this. Human error is my friend

On that same note check to see if a lead is poking through one of the eyelets a bit far and making contact with the chassis.

OH! and check the the contacts on the tube sockets. With ceramic sockets you can wiggle the solder lug and tell if a contact is loose if you have a tube in it, (and amp off, caps drained etc.)

you can tighten a contact with a small pick pretty easily.

Ray

[jeff]

What are you getting for DC on the pots and where are you measuring from?(spot on the chassis?)

[sluckey]

I found that I have dc volts on all three lugs of the volume and tone pots........ I am using a Hoffman ground buss connecting the pots, jacks "isolated" and the preamp all bolted to the chassis. The pot housing, jacks and the ground bolt all have dc volts on them- "they are all connected together". Any help would be greatly appreciated.

You have a grounding problem, most likely in the power supply area, maybe the power transformer HT center tap. Or filter caps ground. There are 3 jumpers on the back side of the board and they are all ground connections. Verify these are correct.

Do this... With amp off, connect the black lead of an ohm meter to the HT center tap (hopefully it's bolted to the chassis). Now connect the red lead to the volume pot ground lug. Resistance must be zero ohms. If not, find out why. Repeat the above resistance check but move the red lead to the negative end of each filter cap. Again, all these readings should be zero ohms.

[sluckey]

Which Hoffman 5E3 layout did you follow? There's and old version that is correct, but the new version is missing a ground jumper on the back of the board. Here's the old...


And here's the new...


The new is missing the jumper between the bottom of the two 220K resistors and the negative side of the 16µF cap to the right of the resistors. I have not looked for other errors on the new layout pic. Just be sure your board follows the old pic and you'll be right.

[jojokeo]

My humble disclaimer... this is my personal thing, hang-up, or what ever you want to call it. This being said....I've seen countless mistakes w/ circuits. layouts, circuit boards, whatever all across their various forms in books, websites, etc... Maybe it's Murphy's Law? But, I seem to come across or notice many bad ones or maybe I've missed updated versions somewhere? 

I do not follow anyone's layout or circuit board or other way of making a circuit for this very reason unless I go through every single component and connection myself. I've said this before and took criticism for it, but I continually witness this time and again in many various forms.

I don't mean this to sound harsh in tone or heavily criticize anybody, but it is what it is. We all make mistakes. There's a lot of frustration when things like this occur by the innocent builder due to none of their own doing. Chalk it up to lessons learned by the best school there is - the highly regarded and esteemed "School of Hard Knocks". 

I apologize for the interruption in the thread.

[Tubed]

PROBLEM SOLVED !
 
The problem was the ground at the chassis. It was bolted down tight with a star washer underneath but that was not sufficient. The fix was to scrape off the paint under the washer. I have never had to do this in past builds before but it is a practice that I will have to start.
Thanks for showing me how to put my ohm meter to good use.
Thank you all, yet again, for your help.

Tubed

[Willabe]

Great, now how's she sound?   

5E3 was my 1'st build and I like it very much to this day.


              Brad       

[stingray_65]

PROBLEM SOLVED !
 
The problem was the ground at the chassis. It was bolted down tight with a star washer underneath but that was not sufficient. The fix was to scrape off the paint under the washer. I have never had to do this in past builds before but it is a practice that I will have to start.
Thanks for showing me how to put my ohm meter to good use.
Thank you all, yet again, for your help.

Tubed

Funny how simple things are in retrospect!

[Tubed]

Sounds great, a little heavy in the bass but that's why I built it. Low output single coils is a good fit and being only 12 watts I can turn this baby up! and it's not to loud.

Tubed