Crackling and popping noise from JTM45 build

[kanderson70]

So I built a JTM45 and used the Metro spec PT and OT. I also added the PPIMV on the back. The amp does work but there is an awful crackling and popping that happens with or without a guitar plugged in. I've scoured the interwebs for clues and came to two possible conclusions. 1. Bad preamp tubes 2. Bad solder joint. Well I've gone through and changed the tubes, crackling still there. I've gone through and re-flowed all the solder joints on the tube sockets and board, crackling still there. I read somewhere that a 250pf cap could be bad. I changed that one and still crackling and popping. This is getting very frustrating. Any help on this little bit of information would be greatly appreciated. What to check next?

This is only my 3rd build so I'm sure it's something silly I screwed up on.

[pompeiisneaks]

One of the best things to try after what you've tried, is to get a wooden chopstick (NO METAL) and probe around the amp. Touch every component and solder joint to see if the noise gets worse or dissapears. That helps narrow down where it's orginiating from. You could also try taking one tube out at a time starting with the first preamp tube, and see if the sound dissappears. That helps you localize where the sound is coming from. It should be around that tube when the noise is gone. Starting with the first tube and moving towards the power side allows the signal to still travel through the rest of the amp if it's not originating in one of the earlier stages.

~Phil

[romberg]

My guess would also be a solder joint or bad pot. Try and narrow down where in the circuit it originates from. Pulling tubes can be effective here.

Pull v1. If the crackling goes away then you know the culprit is associated with the the stages that use V1. If the crackling does not go away then the problem lies down stream. Pull v2 next and so on. Find the point where pulling a tube out (do this when the amp is off of course) makes the noise go away.

Mike

[kanderson70]

One of the best things to try after what you've tried, is to get a wooden chopstick (NO METAL) and probe around the amp. Touch every component and solder joint to see if the noise gets worse or dissapears. That helps narrow down where it's orginiating from. You could also try taking one tube out at a time starting with the first preamp tube, and see if the sound dissappears. That helps you localize where the sound is coming from. It should be around that tube when the noise is gone. Starting with the first tube and moving towards the power side allows the signal to still travel through the rest of the amp if it's not originating in one of the earlier stages.

~Phil

Thanks so much Phil I will give this a shot this evening!

[kanderson70]

My guess would also be a solder joint or bad pot. Try and narrow down where in the circuit it originates from. Pulling tubes can be effective here.

Pull v1. If the crackling goes away then you know the culprit is associated with the the stages that use V1. If the crackling does not go away then the problem lies down stream. Pull v2 next and so on. Find the point where pulling a tube out (do this when the amp is off of course) makes the noise go away.

Mike

Excellent info! Thanks I'll give it a go tonight.

[kanderson70]

Well didn't get around to trouble shooting but I did build Slucky's amp cradle. This will be handy

[pompeiisneaks]

Cool, if you can get a bit more light and a clearer photo, people may be able to see something obvious as well, I can't make out much on taht one due to it being pretty blurred. I've got a hacked up cradle similar to that as well

~Phil

[kanderson70]

Here you go. I'm a little embarrassed as my builds seem to look like dog vomit after he ate a VCR. I'll use the removing tubes and chop stick method tonight...for real this time.

[pompeiisneaks]

I don't have a ton of time at work to pore over it, but also I think you doing the testing first may help us to know where to look. I too get annoyed that my builds don't look like works of art, at quick glance I see a few joints that may need a bit of touch up but nothing that looks dangerous or wrong, I didn't stare at everything though.

~Phil

[kanderson70]

No worries Phil! Thanks to you guys I found the issue using the two methods you and Romberg showed me. It was a bad solder joint underneath the board. A wire from the 2 100k resistors to the 10k resistor was reaking havok on me. Since it would have taken a bunch of time to unsolder everything and turn the board over I ran another wire from the top and off the side of the board. Not the prettiest fix but it worked. Thank you guys so much for helping me figure this out! You guys rock! \m/..\m/
Thanks,
~ Kelly

[pompeiisneaks]

Excellent, glad you figured it out!

Phil

Sent from my LG-H932 using Tapatalk

[M Fowler]

Going over your photo I noticed a bunch of questionable solder joints but it's only a photo not in person inspection by me.

Another thing I noticed was long wires extending through the pot connection holes which from a photo view looked very long and might be touching pot case.
I would go through the build and trim off any long wire leads on your solder joints.

Mark

[kanderson70]

Thought I'd follow up on this thread with the finished result. This amp is a fantastic sounding addition to my amp herd. It will endure some gigging duties next Spring. I don't make amps for other people so I tuned it to my liking. It may not win a bueaty contest for the wiring but it's quiet as a mouse and solid as a rock. I built the head cab and covered it with tolex (my tolex skills are lacking). Then found a cool Pontiac emblem that fit perfect on the front. The ppimv works great on this and was really impressed by the Chinese kt66s (also I've gone back to the tube rectifier instead of the solid state plug I have in the photo). I've put black powder coated corners on since this photo. Anyways thanks to all the wonderful help you guys offer. Oh and BTW... crackling and popping has been fixed in case you didn'tread the whole thread.

IMG_20181014_172343_425.jpg

20181014_163314.jpg

[Reeltarded]

Looks like a proper amp! Love the logo too!

Bad!! Bad!! Ditch the tube rectifier! It's a primary failure point and silicon is almost unkillable if you triple up... and they cost almost 20 cents for the 6.

[FourT6and2]

I know you fixed the issue (what was it?). But from the looks of it, you've got a bunch of ground loops. For example you've got a nice bus wire between the pots and board to which you've grounded some things. But then you've got one of the pots grounded right to the chassis instead of the ground bus? And the ground bus is grounded to the chassis in two different places. You really should only have one connection to chassis ground, not like 5 on the same ground plane. I know you say the amp sounds good, but I'm willing to bet if you address your grounding issues, it will sound even better and lower the noise floor.