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previous: Jeff Lynch I just finished my 5e3 project and ... -- 8/18/2003 12:50 PM view thread

Re: Crackling intermittently on Mission 5e3

8/19/2003 1:19 PM
Jeff Lynch
Re: Crackling intermittently on Mission 5e3
The problem has been found. Here is what happened. I tried replacing a known good tube for each of the preamp tubes. The problem persisted. I pulled each preamp tube one at a time then turned the amp on. When I got to V2 (12ax7) the crackling stopped. So, with V2 out of the circuit, no crackling. By the way, when I tapped on the chassis with a plastic prod, I got all sorts of strange sounds, even a radio station at one time. That made me think of a spark gap which was an old way of receiving am radio (right Bruce?). A spark gap meant a bad solder joint. One of the suggestions was to touch up solder joints.  
I focused on V2 since it was the one that quieted the amp when it was pulled. I re-soldered all of the pins on the tube socket then put the tubes back in and fired it up . . . no crackling! No am radio, no obnoxious noises. Excellent!  
I think the problem was the jumper that I used between two adjacent pins on the socket. I found it very difficult to solder a jumper because when I soldered one end it made the jumper hot enough to melt the other end and it would fall off. Any suggestions?  
So the conclusion of this crackling problem was a bad solder joint. I learned a bit about troubleshooting; substituting known good tubes, pulling tubes to isolate the problem. Even the AM radio spark gap clue! Good luck to the others who are searching for their answer. Jeff

Aaron try using a heat sink clamp on the ... -- 8/19/2003 2:01 PM
Novetti Congratulations man!... -- 8/19/2003 3:36 PM