F-1X crackling sound

[0vid]

Hi


Fired up the F-1X, not used it for a while. It works but there is a crackling sound like a fireplace with wood burning. It is not hiss or white noise, but crackle. The preamp works, the crackling seems to be the same level if the volume is up or down - it is audible enough to be unprofessional. With nothing plugged in the crackling sound is there too.....


Changed at least 6 different tubes, all with the same result of no effect, anyway the amp works - the tone is fine, the EQ works, but the crackling is there. It wasn't before. It is not dust in the pots, the pots are fine.


Any ideas?

[BeenDown139]

well if it was me, i'd break out the tone generator, scope and schematic and start from the output and work backwards to the input.  sounds like you've eliminated the easy fixes.  ya might try a shorting plug across the input, see if that makes it go away.  a detailed examination of all the solder joints might be in order.  kinda depends upon your level of technical expertise.  i've done a lot of analog circuit design and repair so that's the lens i look at stuff like this through.

good luck, happy hunting and don't blow anything up.

[adriaan]

Not sure, but exercising the efx loop jacks is good for solving similar problems.

[0vid]

Fixed, quiet now. Changed the sockets for fx loop, and output. Used generic sockets, what I have to hand in my parts bin, not switchcraft so had to solder a ground wire to connect. Fit a Mesa boogie 12ax7, tried several. Checked power supply, the cable feeding the preamp and the source were changed. Haven’t determined if it is power source or cable - but the noise is gone. I’ll check the true source of the issue in the morning.