I got a redhead in. It has a preamp noise issue. It's present in the headphone output. Someone has taken it apart. And I put it back together to get an idea of any issues. Tweeter was disconnected. One speaker dangled. It has one Eminence and one PAS. So that's strange.
It has a new preamp tube. So it seems. I took the amplifier out of it's chassis. And everything looks nice. It plays. Only that hum is present.
The current preamp tube is a SOVTEK 7025.
I expected a loose wire or something stupid. But when I checked all leads everything seems fine.... But... That hum is there... The hum you have when one wire is disconnected.... That kind of noise...
It has a new preamp tube. So it seems. I took the amplifier out of it's chassis. And everything looks nice. It plays. Only that hum is present.
The current preamp tube is a SOVTEK 7025.
I expected a loose wire or something stupid. But when I checked all leads everything seems fine.... But... That hum is there... The hum you have when one wire is disconnected.... That kind of noise...
OK, you have hum. Hum is a pretty common complaint in audio gear.
You mention speakers, so I assume this is not a preamp only unit. Does turning down the volume controls turn the hum down? Do the tone controls change the tone of the hum?
Is this an SWR Redhead? Or is it a Fender era SWR Redhead?
Start with power supply. Are the main rails even and free of ripple? And the tube plate power, is that clean and up to voltage? And finally, the 15v supplies for the op amps, are those both up to voltage and free of ripple?
You mention speakers, so I assume this is not a preamp only unit. Does turning down the volume controls turn the hum down? Do the tone controls change the tone of the hum?
Is this an SWR Redhead? Or is it a Fender era SWR Redhead?
Start with power supply. Are the main rails even and free of ripple? And the tube plate power, is that clean and up to voltage? And finally, the 15v supplies for the op amps, are those both up to voltage and free of ripple?
It's present in the headphones out. I traced it down to the jack input. But can a jack break internally? Cause if I earth the jack to earth it's quiet. I resoldered all leads. Looks like the jack chassis itself is at faulth. But it's tight and looks great.
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