Electro Stimulation Ward > Signals and Noise

Tracking down noise

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S Clark:
I had a low level noise in my main system for a good while... couple of years.  I thought it was an issue with a tonearm.  Looked at finding someone to polish or replace bearings.  Over time, the low level noise became more intrusive and sounded like a dirty volume pot in my Dodd pre... only randomly and without the volume being touched.  But finally I desoldered and put in a new Alps.  It was a pain in the ass, and fortunately Rich H was available to guide me to the correct replacement.  But that wasn't it.  And then  :duh, I decided to replace the 6H30DR tube... success!!!  For a day or two.   
Time to call the pros.  I talked with Charlie Cocci, who has most of the schematics for Dodd gear.  We decided to replace a board, and Charlie had an extra on hand to send me.  A week later it arrives.  The unit is plugged in but the case is off and I start to look at the board.  It's got a pin connection that I touch... and the noise appears.  I wiggle it again, and the noise appears.  I wiggle another pin connection, and the noise appears.  I call Charlie, and after a liberal spray of Caig De Oxit and a good scrubbing with a set of brushes for tube sockets, the noise is gone. 
A year or two has gone by, and all it really needed was to take the internal connectors loose, clean them, and put them back on. 
This has been a hard lesson learned.  Corrosion is insidious.  Take the case off your gear occasionally and clean all contacts.  It will be on my list of annual things to do. 

Nick B:
That’s quite an adventure/ordeal and over quite a long period. Glad you had the persistence to get it resolved. How long have you had the Dodd?

S Clark:

--- Quote from: Nick B on September 20, 2021, 07:39:06 PM ---How long have you had the Dodd?

--- End quote ---
Probably 6-7 years. I've got one of his first battery preamps in my other system that I've had since around 2006.   They are excellent gear. 

malloy:
So, it was dirty and loose pins in the tube sockets?

The amount of troubleshooting you performed is indeed something. To summarize the list of suspects: Tonearm bearings > Volume Pot > noisy tube > new board > pins

This would have made me go mad, but of course, things like these you just cannot 'let go', that is why you are in the hobby.

Reminds me of a smaller ordeal I had after having my amp serviced. One channel would go dead, but of course the fault only showed itself when I was listening and never at the repair shop!

BobM:
I agree that your diligence is commendable. The first, very first thing to do with any troubleshooting problem is to isolate the true source of the noise. To go from a turntable to an amp as the source means you didn't successfully perform that first exercise. Something as simple as identifying that the noise happened on both a turntable and a CD player would confirm that the noise was indeed somewhere after the source component in the chain.

I'm glad you finally found the problem without having to fully replace your amp. I don't know if I would be as successful a sleuth to open it up and check the pins and connections, but that was indeed a stroke of genius. Clean connections ... who would have thought they mattered (sic)?  :duh

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