nelsress begins his WOPL 400 project

wattsabundant · Mar 12, 2015

And therefore the Zoebel networks on Don's board need to go. The two blue resistors tied together and the two small blue caps..

R1, R2, C8 and C9..I'll have some recommendations on you wires here in a bit....still studying..[/QUOTE

If you cut off the resistors the capacitors serve no purpose. Cutting the resistors avoids the desoldering iron and the potential for board damage.

laatsch55 · Mar 12, 2015

True dat....

Gepetto · Mar 12, 2015

nelsress said:

Looks like you are making good progress Nelson. Lee already told you about the white wire from the RCA copper plate that has to be removed. The ground for that floating plate and the RCA jack shells comes from the connection to pin 2L and 2R of the control board and that is it.

nelsress · Mar 13, 2015

wattsabundant said:

laatsch55 said:

Thanks Don, that makes it even easier! I'll do it that way, after I have a cup of coffee to wind down a little after a busy night at the pub!

nelsress · Mar 13, 2015

Gepetto said:

Thanks Joe, yes, it seems to be coming along well. Yes, that wire has been has been removed from the copper plate and relocated to the J3-2 on Don's board, providing a ground path to the cap bus bar to the DC protect board. Yes, that makes sense that 2L and 2R provide the ground necessary for the RCA jacks. Seems like PL went nuts with grounding the RCA jacks, between the two ground wires to each of them, then the large guage bare copper wire soldered to the copper plate, plus I assume that small white wire that was intertwined with the blue/black and green/black twisted pair was also a ground as it too was landed in the solder "blob" on the copper plate. Yikes!!

nelsress · Mar 13, 2015

They're outta here!

The Zoebell network has been removed from the DC protect board. I ended up cutting the resistors off first, which were almost against the board and when I looked, the caps were sitting up off the board with plenty of room for my cutters so I just cut them off too while I was at it.

nelsress · Mar 13, 2015

That too Lee!!

laatsch55 said:

Almost forgot that, most important part-state of the art sound!!

nelsress · Mar 14, 2015

Biasing the PL14_20 control board

Tonight I decided to bias the PL14_20 control board. I was going to do that before I installed the DC protect circuit but changed my mind. The instructions were very clear and it was an extremely easy procedure. After attaching my positive lead to the left channel bias test point on the PL14_20 board and the negative lead onto the left channel white binding post I slowly powering the amp up using a variac. I did this very slowly keeping a keen eye, nose and ear (at around 80+or- V I heard the relay kick in) focused on the amplifier's innerds for any abnormalities. That went without a hitch so I then let the amp warm up and when the voltage stopped creeping up (around 0.108 V) I waited another minute and adjusted the trim pot until I achieved 0.355 V. Carefully removing the (+) lead and moving it to the right test point, then the (-) lead to the right channel red binding post, I repeated the process setting it to 0.355 V on the right channel.

Worked like a charm! Now I'm ready for the next step(s). Lee, Joe or anyone looking who knows, do you think I might be able to insert this amp in a system this weekend yet? Brenda's working this weekend and all I've got planned so far is picking up the Ohm Walsh 2's Saturday just after noon. I'm sure I'll stop at one of my favorite haunts for a celebratory slice and a brew for lunch but then I'll be back home again before 2 PM, or thereabouts.

laatsch55 · Mar 14, 2015

EXCELLENT NELSON!!!! No reason not to use it now. With nothing between the amp and the wall plug what do you get?

Gepetto · Mar 14, 2015

nelsress said:

Tonight I decided to bias the PL14_20 control board. I was going to do that before I installed the DC protect circuit but changed my mind. The instructions were very clear and it was an extremely easy procedure. After attaching my positive lead to the left channel bias test point on the PL14_20 board and the negative lead onto the left channel white binding post I slowly powering the amp up using a variac. I did this very slowly keeping a keen eye, nose and ear (at around 80+or- V I heard the relay kick in) focused on the amplifier's innerds for any abnormalities. That went without a hitch so I then let the amp warm up and when the voltage stopped creeping up (around 0.108 V) I waited another minute and adjusted the trim pot until I achieved 0.355 V. Carefully removing the (+) lead and moving it to the right test point, then the (-) lead to the right channel red binding post, I repeated the process setting it to 0.355 V on the right channel.

Worked like a charm! Now I'm ready for the next step(s). Lee, Joe or anyone looking who knows, do you think I might be able to insert this amp in a system this weekend yet? Brenda's working this weekend and all I've got planned so far is picking up the Ohm Walsh 2's Saturday just after noon. I'm sure I'll stop at one of my favorite haunts for a celebratory slice and a brew for lunch but then I'll be back home again before 2 PM, or thereabouts.

Nice job Nelson. It pays off to do the interim checks along the way to ensure the success you just witnessed. Although the relay clicked in you should also measure the DC offset for each channel.

nelsress · Mar 14, 2015

Didn't catch that. Over...

laatsch55 said:

Thanks Lee, Okay I was up late and just woke up, I'm not sure what you're asking? With nothing between the amp and the wall plug...air heavy with anticipation?

nelsress · Mar 14, 2015

Thanks Joe.

Gepetto said:

Could not have done it without you guys! Okay, I'm guessing that won't take long, and if those readings are good, I should be good to go with the LED light panel and meter adjustments, correct?

nelsress · Mar 14, 2015

Just a few things...

A few more questions if I might please:

1. Which document has the instructions for testing DC offset?

2. Are there photos showing the LED light board connections to a full comp WOPL 400?

3. Should I have had the 5 AGX fuses in to adjust the bias or didn't that make a difference. I assume I should install them now, correct? I still have the 3 AGC fuses in that I used for testing.

Thanks guys.

Gepetto · Mar 14, 2015

nelsress said:

Hi Nelson
No procedure really has that, it is just a quick voltage check with your DMM on the output plus and minus binding post terminals. Typically you will see approximately minus 0.010V (minus 10mV) at each output

You can put the 5AGX fuses in if all came up properly. That should not have any effect on the bias setting.

The LED light board connects exactly the same way it did originally.

laatsch55 · Mar 14, 2015

When plugged directly into the wall..what's the bias?

nelsress · Mar 14, 2015

Missing one...

Thanks Joe. I must have missed a wire then somewhere along the line. The only wires I have left are the two white ones coming from OutL and OutR on the backplane boards and the two wires coming from the transformer. Where does the 5th wire come from?

Gepetto · Mar 14, 2015

nelsress said:

Ground at the bus bar

nelsress · Mar 14, 2015

Simple enough

Gepetto said:

Can I tie into the lug on the left heatsink ground as it's connected to the bus bar or does it have to go directly to it without the "step"? Thanks a bunch Joe.

nelsress · Mar 14, 2015

I'm a bit of a dummy

so, of the three, PAD 1, PAD 2, and PAD 3, is the red one right, the left one white and the black one to the ground, in the photo in your instructions? Sorry, I stripped the amp down months ago, guess I should have cut the wires in stead of de-soldering them!!!

Gepetto · Mar 14, 2015

nelsress said:

Sure, not a problem with this Nelson.

nelsress begins his WOPL 400 project

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