Reduction Hum and No Playback [resolved]

[Paul Birkeland]

What AC voltage ranges does your meter have?

 

[OverAnalyst]

600V

 

[Paul Birkeland]

That's as low as it will go?

 

[OverAnalyst]

ahhh, it does measure mV, but will need to dig that up. Fluke 107

 

[Paul Birkeland]

You need to set the meter to MV with the ~, then use an 1/8 to RCA cable to connect your phone to the Reduction.  On your phone, download one of the many free signal generator apps and use it to make a sine wave at 60Hz.  With the volume all the way up, you should see 300mV to 500mV at the ends of the RCA plugs with the 1/8" end plugged into your phone. 

Let me know when you're there and we can proceed with tracing some signal in your amp.

 

[OverAnalyst]

confirmed. I get get 400mV

 

[Paul Birkeland]

Groovy!

Plug those RCA cables into the Reduction, leave the Reduction off, then measure the AC voltage across the RCA jacks.

 

[OverAnalyst]

so I took measurements from the nut and the center of the plug. On the both A and B sides, I read 400mV.

 

[Paul Birkeland]

OK, now you'll want to turn your phone down till you see about 10mV coming into the RCA jacks, turn the amp on, then read mV between ground and terminal 6 as well as ground and terminal 27. 

 

[OverAnalyst]

6 - Around 130mV and fluctuating
27 - Around 140mV and fluctuating

 

[OverAnalyst]

On a side note, I take a resistance reading from the ground tab on the RCA to the nut. They should essentially have zero resistance, correct? I get about 23kOhms for both A and B side.

 

[Paul Birkeland]

I would double check that the ground tab is installed just under the nut, not under the plastic washer.  In your photos it was hard to see the buss wire going to the ground lugs on the ground post, but I saw two wires folded over each, so it looks as though they are there.

 

[OverAnalyst]

Yeah, that's what I was trying to explain back on reply #19, but poorly. I have the plastic washer between the ground tab and the nut. ARRGGGG. I'll spend this evening fixing.

 

[Paul Birkeland]

You aren't the first person to do that, don't worry! 

 

[OverAnalyst]

So that RCA ground tab/washer was the issue. It amazes me how one "little" thing can cause quite a showstopper. Just spent the last few hours listening to some records. I'm definitely pleased. I purchased the upgrade kit as well, but will wait till I'm ready.

Gotta say, it was pretty cool learning about that trace signaling. I've heard it before, but never knew what it was.
Thanks for your help and patience PB. Much appreciated.

 

[Paul Birkeland]

I'm glad you got it all sorted!