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4230 hum on phono

T

Tom Modica

New Member
I have just replaced the caps on the 400 board (phono pre-amp). the hum has quieted but there is hum still there.

The ground wire is connected. when removed, the hum is MUCH louder. No other modes have any hum (tape, CD, radio). I run volume at 1/4 to 1/3

new patch cords and Doxit used on head shell on TT

what is my next step?
 
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Do you have the bottom cover on? Do you have any hum without the turntable connected and selector switch at the phono position?
 
yes to both, top & bottom covers are on; I just pulled all of the cables, power cord & ground strap...no hum

That means it is in the TT. There are no electronics in the TT. what would be causing it?

It is an ELAC 770H TT

sanjib, thanks for your response
 
A common source of hum coming from turntables, in those with removable headshells, is poor contact between headshell contacts and tonearm contacts. If contacts are spring loaded, make sure they aren’t partially collapsed - spring them out if necessary. Clean the contacts with Deoxit. Try removing headshell/cartridge and see if most hum goes away.
 
I have removed the shell, more Doxit and stretched the contacts. no help with head removed, still hums

I have plugged the TT into the back of the amp and reversed the plug, no help

I removed the RCA cables, the right (red) channel removed, the hum is gone, with the left (white) channel plugged in no hum

I replaced the female RCA jacks under the TT, so they are not carroded. I will switch cables next. White cable good both channels; red cable has hum either channel
 
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