2000 DSL 401 hum static noise, Ground issue??

ksnyder

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New to the site. Bought 2000 DSL 401 for my son one year ago and it worked fine. About a month ago it began humming and static type noise. Found this site and tubes were listed as a common problem. pulled tubes and found corroded pins. Replaced all tubes with a set a JJ tubes. I could see a terrible solder job on tube sockets and hoped it would be ok. Seemed to clear up the problem for abut a week then the static sound returned. I pulled the circuit board and found a mess. Santa delivered a Hakko solder station to enable a proper repair. Old soldering iron retired. The Hakko is great. The right tool for the job makes a difference. Repaired many cold joints all around the board. one resistor wasn't even soldered, it was hot glued. Assembled the amp and sounded better than it ever had. After several days my son noticed the speaker was breaking up only on the low e string. I figured a bad speaker so I removed the 20 year old speaker and installed a Eminence V1216. Sound great for a few minutes then the volume double or drop by half or cut out. I discovered that touching the faceplate would change the volume and create or remove hum. I pulled the amp think there might be a ground issue. I haven't found anything yet. I made a cradle for the amp to simplify service. With the amp on I could touch the chassis with my finger and it sounds like I'm scratching the speaker. If I tap the chassis I hear it in the speaker. I checked the ground from the plug to to the chassis and have continuity. The volume pot works but sometimes the volume will cut out or hum. I ran a jumper from the ground terminal at the plug to the chassis but it made no difference. I don't know what to look at next. The volume pot might be going but the noises from touching the faceplate and chassis has me puzzled since the ground jumper doesn't change the issue. I'm a little rusty on electronics. I left mechanical engineering 35 years ago. I built a Heathkit stereo 50 years ago, yea I'm old. Any ideas or helpful hints would be greatly appreciated.

Kurt
Northfield VT
 

South Park

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Greetings . Check your earth ground on the plug
 

JohnH

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I like this amp, I still have mine after 14years since new. But its quirky and complicated, and the board and solder joints get stressed by heat from all the tubes underneath.

A complete carefull and systematic reflow of all solder joints can fix problems that you aren't aware of. Lubricated contact cleaner can help the tired switches and pots
 

ksnyder

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Thanks for the responses. Checking the ground connection was the first thing I did and it is good, which contributed to my puzzlement. I have a volume pot ordered as the shaft has a bit of wobble. I am in the process of reflowing every solder joint now. The PCB had been overheated in the past which lifted a few areas, which have crappy looking repairs but they have continuity. I've never repaired pads on a PCB so I'm hesitant to mess with an old repair that is functional.
I have DeoxIT D5 and CRC Electronic Cleaner. Neither one mentions lubrication properties.
Is there a recommended lubricated contact cleaner?
Full disclosure. I don't play guitar, I'm supporting my 15 year old son.
 

ksnyder

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Success. Reflowed or desolder/resoldered every point on the PCB. The amp sounds great while playing and quiet between songs. My son is happy, I'm happy. Thanks for the help.
 


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