| Author | Message | ||
     Jeff Economou Olson (jcolson) Username: jcolson Registered: 02-2007 |
I have a HD one thirty head running through a MM 4x12 cab. I've been the owner for about 6 years. I lived out of the country so its been sitting still in the basement half that time. In the past few months its been making a loud, consistent, crackling noise when at high volumes or when bass notes are resonating loudly. What could this be? | ||
| Mike Kaus (mm210) Username: mm210 Registered: 05-2006 |
Just a guess(but a pretty educated one!) you need to look at two things. Especially since you say it's been "sitting" for a while. First thing is to clean and re-tension the tube sockets. this requires that you "FIRST" drain the filter caps of all voltage(a 10k resistor with a wire attached and go from ground to the "+" side of the filter caps.) and then, using a small pick like a dental instrument or something similar, bend the little grabbers in a little to increase the tension on the tube pins. Then, using something like de-oxit or similar, put a little on the tube "grippers" and insert the tube in to the socket and run it in and out. This will clean the tube socket. Let it dry, insert the tube and fire it up. If noise gone-quit while you're ahead. If it's still there, I would look for bad, cracked resistors. The old carbon comps are bad about cracking and making a LOT of racket. You minght have to do a little probing with tha amp ON with a plastic or wooden(NOT A PENCIL) probe. Remember, this amp has 700v running around in there so it WILL kill you if you're not careful. If ANY of this sounds scary to you or you are not comfortable with it, have a person who is a professional do it. It can be done but it IS dangerous. | ||
| William Michel (bill) Username: bill Registered: 12-2006 |
Why not a pencil? Does the graphite conduct electricity? I had same problem with a 150 combo. One amp tech. later and small board resoldered, charged 100 for crappy sovteks I didn't need, and a brisk whisk out of the door, and problem still there. Not worth fixing because I need the parts more than I liked the sound. Still, some small voice in me says 'fix it'. | ||
| Mel Hadden (merkle) Username: merkle Registered: 01-2007 |
Yes, graphite does conduct electricity. Not as well as copper or gold but with the high voltages why risk it? Try a dry popsicle stick or a plastic stick. | ||
| William Michel (bill) Username: bill Registered: 12-2006 |
Thanks. Been using a rosewwod chopstick. Funny thing is, all you have to do is to touch the PI board ANYWHERE, even very lightly, and sound drops out, big loss of volume. I know Terry could fix it, just fearful I'd weary anyone with desire to know why it happens. Found a mint equivalent made a few days apart...maybe too clean for my style. I never plug in, preferring the older trem models. BIG crackles, even took out a speaker with the jolts it put out. Finally I ruined the 8 pronged chip by inserting two legs into one hole in socket, my bad. Now it makes no sound at all. Problem solved. Cab is slated to take supposedly clean 130 chassis....maybe a mod is in order for unused 150 chassis. I am REALLY unhappy with what a local tech did, at the last minute, to the PI board. Sad. No respect for printed boards, momma told me not to go... |