Leroy's 700B

[laatsch55]

Yes it is.
PB 2020

 

[Gepetto]

Yes it is.
PB 2020

The new pinup at PL

 

[laatsch55]

Time to test...

 

[NeverSatisfied]

Hey Lee, what is the PL until under the Oscope ?

 

[laatsch55]

That is Phase Linears factory RIAA curve tracer. I also have the engineering departments 2,000 watt load cell..even has a pl property sticker on it .

 

[NeverSatisfied]

That is Phase Linears factory RIAA curve tracer. I also have the engineering departments 2,000 watt load cell..even has a pl property sticker on it .

Now that is cool…..the stuff that built the stuff.

 

[laatsch55]

Yep...

 

[Turboj5525]

Man what I would do for this 700... such excellent work. Absolutely gorgeous.

 

[laatsch55]

Residual noise....not good..

 

[laatsch55]

Pot movement has an effect. 5mv, pot attenuated, 10 mv, not

 

[laatsch55]

Ran a sweep from 9.5 hz to 80Khz...same through out frequency range. Small variations only..

 

[laatsch55]

Sweep...

 

[J!m]

Maybe useless and unrelated but when I went from a conductive plastic pot to the stepped attenuator my headphone amp came alive.

I’m sure the old wiring has a part in it but it cleaned up SO MUCH after that change. If you going full-retard on it, it might be worth the effort and expense. (And maybe not?)

 

[laatsch55]

This is all new wiring Jim...

 

[J!m]

But were you saying using the pot was adding some noise?

That’s what I was referring to. Changing the pot to a resistor ladder.

And on my headphone amp, it was all new- wiring, pot, board, enclosure and every component on the boards

Huge difference.

I will use them whenever I can now. I’m a changed man.

EDIT- by “old wiring” (which I now understand the confusion), I meant the way I had originally implemented the pot wiring to the board. Signal entered the board and then immediately jumped out to the pot and back. New wiring goes from input jacks direct to the attenuator which runs directly into the board; no more in/out and added wire running over the output buffer…

 

[laatsch55]

Ahhh.....

 

[laatsch55]

Diagnosing the noise monster...

Knowing Perry would not have let a 10mv residual noise amp out of his sight I have been backtracking what I've done.
1`----Replaced the #18 speaker out wires with #16 from the backplanes to the DCP
2----Replaced a malfunctioning "Trojan Man" DCP with one of Don's. DCP was shorting Speaker + to Speaker - , would not pass DBT.
3----Did away with the Ser II faceplate with the 400 meters in it.
4----Added 2 --700 meters in a Joe faceplate with a NOS PL Power switch, and a barrel type PL meter range switch.
5--- Added a Joe light board
What I've done to diagnose the problem.
1----unhooked and taped off meter feed wires from the light board to meters------ No change
2---desoldered the meter range switch-----No change
3---desoldered 12 volt board feed-------No change
4---desoldered meter feeds from "out" trace on backplanes to light board----No Change
5---Dismounted faceplate------No change
6---Unhooked Speaker out wires from backplanes to DCP----No change

 

[Skratch]

I don't know if it makes a difference but the VU meter board is 6 volt

 

[laatsch55]

Not this one, custom build for a Ser II transformer...

 

[Gepetto]

Not this one, custom build for a Ser II transformer...

Lee twisted my arm many years back...