New Construction. Some issues solved. Some not. Need advice.

[harv-e]

Decided to ressurect my turntable and record collection.  I took great care of them and they sound great (for the most part).  So then, time to upgrade my preamp, wandered across the Bottlehead site, was impressed, and here I am with my completed EROS.  No difficulty with construction, though I have some difficulty stripping wires, even though I bought a new wire stripper just for this project.  I followed the testing procedures throughout.  First problem was with ground to one of the tube sockets.  Close inspection showed that I had soldered the insulation covering the wire, actually missing the wire completely!  After final completion, all voltages/resistances checked.  Fired it up - horrendous noise in left channel only when attached to the turntable.  Switched plugs.  No effect.  Took it all apart, including circuit boards, and resoldered everything I could see.  No luck.  Somehow I moved the input wire from the phone IN jack with my finger as I was becoming frustrated........and the noise stopped.  Close inspection showed that the ground wire was broken inside the insulation from the ground lug on the jack!  UGH.

OK.  Now it's working!  Next two issues.  There is a distinct hum when I turn up the amp.  But I am reading that I need to burn things in a bit more, so I am not too concerned about it.  However, there is a definite "motorboating" sound that I cannot isolate by changing tubes or inputs, that seems to be coming from both channels.  Power supply issues?  I cannot find anything in the forum searching for "motorboating," but I don't know what else to look for. 

So any help would be appreciated!

Thanks from the newbie!

Harvey

[Paul Joppa]

First thing is to get or make some shorting plugs - RCA plugs that are internally shorted, either with wire or a low-value resistor (100 to 1000 ohms?). Cheap plugs from Rat Shak will do, and they will come in handy for years to come. Plug them into the input, thus removing the turntable and its wiring from the equation. If the hum goes away, then you've found the problem; otherwise you've at least eliminated one possibility.

Checking the connection between Eros and the preamp is more difficult, depending on what the preamp is and how it's powered (2- or 3-prong plug? Can it be reversed? Are they on the same power circuit?)