So I picked up an MX 112 tuner preamp that had no audio out on one channel and extremely distorted audio/static/popping out if the other channel. There was obvious physical damage to the internals of the bass attenuator so that pot was replaced. That gave me audio in both channel, one still being very distorted. After tracing the signal I came to find the volume pot had an issue as well, one of the "gangs" on it was introducing a lot of garbage into the one distorted channel. So it went as well. I went ahead and hooked it up to a small amp and some speakers (both expendable) to see where I was at. Upon power up I would get about 7-10 seconds of somewhat loud crackling/rushing water sound and the same after I would power the preamp off. I got no audio until I hit about 9 o'clock on the volume with one channel still a bit distorted and quite a bit lower in volume then the other channel. As soon as I hit around 12-1 on the volume both channels came in clear and somewhat equal in loudness. I could turn it back down to 9 and both channels still coming in clear, but still no sound below 9. I let it play for a couple of hours and it sounded great the whole time. I powered it down and no crackle. Powered it on a couple of hours later and no crackle, but a little uneven in volume some distortion when turning volume up and down. By this point every potentiometer had a couple good deoxit sessions.
I unplugged the preamp for the night and powered it up the next morning and got the turn on crackling and water rushing sound along with uneven volume. I know this series had many issues with the pots so I took another look at the volume pot. Signal going into both channels are identical. Signal coming out is quite distorted, one trace is quite a bit lower than the other and catches up as you go up in volume.
Last night I decided that my next step was to do a full recap as I've read that's usually the remedy to eliminate the power on crackling and I thought may contribute to the other issues I'm having as well. The reason I went with this thought is that I thought it was weird that I was getting almost no sound out of one channel until I turned it up to 12 and still had audio after turning it down. So my thought was the carbon trace wasn't open. This morning I woke up and saw a person I subscribe to on youtube was having an issue with his MX 113 volume pot and it was a video on replacing it (ElPaso TubeAmps if you're curious). Now that I know the power/volume pot isn't impossible to get it's an option, a $100 option, but still an option.
If I replace the pot and it works I'll skip the recap right now, if I recap and that works then I'll skip the pot. Just trying to get an idea of what my next step should be. I appreciate any help I can get!
Thanks,
Dan
I unplugged the preamp for the night and powered it up the next morning and got the turn on crackling and water rushing sound along with uneven volume. I know this series had many issues with the pots so I took another look at the volume pot. Signal going into both channels are identical. Signal coming out is quite distorted, one trace is quite a bit lower than the other and catches up as you go up in volume.
Last night I decided that my next step was to do a full recap as I've read that's usually the remedy to eliminate the power on crackling and I thought may contribute to the other issues I'm having as well. The reason I went with this thought is that I thought it was weird that I was getting almost no sound out of one channel until I turned it up to 12 and still had audio after turning it down. So my thought was the carbon trace wasn't open. This morning I woke up and saw a person I subscribe to on youtube was having an issue with his MX 113 volume pot and it was a video on replacing it (ElPaso TubeAmps if you're curious). Now that I know the power/volume pot isn't impossible to get it's an option, a $100 option, but still an option.
If I replace the pot and it works I'll skip the recap right now, if I recap and that works then I'll skip the pot. Just trying to get an idea of what my next step should be. I appreciate any help I can get!
Thanks,
Dan
