Fucking hum

I have no hum but then I don’t cling to antiquated means of music reproduction.:smiling_imp:

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You have my sympathies.

Yeah, but your post stinks

:smiling_imp:

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OK, so it is an earthing issue then. If there’s no fault in any of the kit then hum is almost always an earthing issue.

I was able to find the schematics of the amp online but I suspect diagnosing the phono stage and TT (including arm) earthing would be more of a challenge, not least because people swap the wiring around inside TTs in an effort to eliminate, um, hum.

If the kit was mine then I’d be opening it up and tracing the earth paths. The alternative is essentially a trial and error routine of attaching earths here and there. Both approaches can lead to a solution and there’s no guarantee that earth tracing will be quickest.

When you connected the TT to the amp’s phono input and found you got hum from the R channel only was the amp still jumper-wired to mains earth ?

VB

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Yes.

The only approach I have ever tried that actually worked. Eventually.

The amp appears to be symmetrically earthed, so unless it’s been modded any difference between the two channels must be due to a difference between the L and R wiring inside the TT/arm.

I wonder if when you only had hum on one channel it was caused by one thing in the case of the external PS (say the L channel cable screen then not being earthed and the R channel one being earthed via the arm lead earth) and by a different thing in the case of the amp’s internal PS (say the L channel screen then being earthed but the R channel screen now carrying some kind of ground loop hum involving the arm earth) ? If you earth the amp, use its internal PS and don’t connect the arm earth to the amp what happens ?

VB

This just gets more strangerer, I have put the Luxman back in, which worked faultlessly before; hums like buggery with the TT selected. Tried all the same combinations with earthing, connect direct to amp, connect via PS, hum. I had all but had enough and pushed the amp back into the rack, hum stops, play a record, no hum but only one channel. Check connections, right hand speaker had become disconnected, push banana plug back in 2 channels but hum. Disconnect one of the left speaker plus, one channel and hum :hot_face:

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Have you tried it without the earth lead

Yup, very loud hum :drooling_face:

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Can you continuity test the earth leads to see if one has failed in the unplugging plugging in process.

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Not sure if it’s relevant, but the arm lead is microphonic.

I’ve had microphonic arm leads before, I don’t think that will have anything to do with the hum problem, I don’t know what else to suggest.

Anyone local to you that could pop round to take a look?

Change all the interconnects. A dodgy connection can cause hum. Unplug them all and gradually reintroduce.

It does it with just the TT plugged in, so could be the arm lead. I need to get it tested.

No arm in that.

:flushed:

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FIXED!!! Took the base board off, earth wire from plinth to motor unit had become detached :angry: I am the man :face_with_raised_eyebrow:

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‘Become detached’ all on its own?

You expanding your skill set from just killing cartridges to whole decks now?

:rofl:

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image
High precision tools used.

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Reattached using ‘Old Faithful’?

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