PL400 Series II WOPL Quasi Control Board

Gepetto

Gepetto

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Sunnbobb said:
Joe, the first picture in the thread is this board.
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Please unlace your ty wraps going into the control board and post new pics so we can see what you have going on. I am unsure what you are doing with that white ground wire...
 
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First thing, the long white wire that you have running directly from the bulk capacitor bus bar lug to the copper plate under the input jacks. cut it somewhere around the middle of the control board, strip the end attached to the bulk capacitor lug and terminate this stripped end into the LEFT channel terminal position #5. This will establish a ground reference for the control board. Remove the white wire that you have going into the RIGHT channel terminal block position 5. leave this terminal block position blank, no connection. Then with NO inputs connected to either the left or right channel positions 1 and 2, measure the output offset and see if it now hovers very close to 0 volts. We can deal with the input wiring after you get this settled down.
 
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Wow, I'm not worthy! That fixed the output voltage and output relay issue. Output voltage is pretty much zero. thankyou thankyou. Now my ears are open with the input arrangement.
 

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This diagram should help, it is for a 700B but the wiring is similar. Remove that white wire going to the RIGHT channel terminal position 5. That should be OPEN. The input signals only interact with terminal block 1 and 2 positions.

Ignore the input switch shown in this diagram, the 700B has this switch but the 400 S2 does not.
 

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Gepetto said:
This diagram should help, it is for a 700B but the wiring is similar. Remove that white wire going to the RIGHT channel terminal position 5. That should be OPEN. The input signals only interact with terminal block 1 and 2 positions.

Ignore the input switch shown in this diagram, the 700B has this switch but the 400 S2 does not.
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Should I be running a new wire between the copper plate and the bus, or will the inputs get their ground through 2l and 2r connections?
 
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Sunnbobb said:
Should I be running a new wire between the copper plate and the bus, or will the inputs get their ground through 2l and 2r connections?
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NO wire between the input jack copper plate and the bus. That creates a ground loop.

The input jacks receive their ground connection from 2L and 2R as you have stated.
 
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One last question. Can i run r2 and l2 from the copper bar, rather than all the way back to the pots, since pot post 3 (ground) already runs to the copper bar?
 
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Sunnbobb said:
One last question. Can i run r2 and l2 from the copper bar, rather than all the way back to the pots, since pot post 3 (ground) already runs to the copper bar?
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No. Not all grounds are created equal, it is important to follow the diagram or you will create a ground loop with its associated noise and hum.

I know that this is not that intuitive but it is important.
 
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Gepetto said:
No. Not all grounds are created equal, it is important to follow the diagram or you will create a ground loop with its associated noise and hum.

I know that this is not that intuitive but it is important.
Click to expand...
"Not all grounds are created equal" Boy, that sounds like you have been hanging out in my shop working on Italian Motorcycle wiring!

Thanks for the tips boss. I really appreciate it.
 
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Hi Joe, sorry I had to take a break for other things, and I just finished buttoning it up. Onward to real speaker testing. No fires or booms so far! Thanks so much for the guidance.
 
Artied2

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Hi all. I'm following these threads closely. (Trying to make a decision on my 400 II.)

I notice that the "white wire" ground problem, identified in posts #24 & #25, is precisely what is described in the WattsAbundant relay installation procedure. I take it, that instruction is wrong.

As shown here: 400 Relay Installation Procedure

You have to scroll to the bottom to open the PDF.
 
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Artied2 said:
Hi all. I'm following these threads closely. (Trying to make a decision on my 400 II.)

I notice that the "white wire" ground problem, identified in posts #24 & #25, is precisely what is described in the WattsAbundant relay installation procedure. I take it, that instruction is wrong.

As shown here: 400 Relay Installation Procedure

You have to scroll to the bottom to open the PDF.
Click to expand...
Sorry, it is somewhat complicated.

There is the guy who wants to install the quasi comp board quickly with minimum alteration to the internal wiring. He gets one set of instructions.

Then there is the guy who wants to max out the quasi comp board performance and is willing to make some key alterations to the internal wiring. He gets the more advanced set of instructions.

In those posts you referenced, I was giving Richard the more advanced wiring tips.

Then there is the go for the full monte approach, bare metal upgrade. That follows the complete teardown, backplane installation along with control board. And after gutting it following the very detailed rewiring upgrade to make it into a full comp amplifier. That nets the best possible performance.
 
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Excellent. "Advanced" is what I prefer. So, the WA relay will still work if wired using the preferred grounding technique described in this thread?
 
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