Gibsonian's Cherry Pl 700 Ser I, soon to be a PLWO-1000

[laatsch55]

Lowest bias setting of 432mv, offset was .001mv, highest bias setting of 732mv, offset was .002mv

 

[Gepetto]

Inputs hooked to the AP with the AP off.

Do you get a different offset with the RCA inputs totally open? That is how I always measure offset. I think you will see a difference, the AP has an output resistor to ground inside it which swamps the 39K to ground on the PL board.

 

[Gepetto]

Lowest bias setting of 432mv, offset was .001mv, highest bias setting of 732mv, offset was .002mv

This is the right channel? If so then the amp is behaving as it should, at least in this regard.

 

[laatsch55]

I have some connectivity problems with this bias tranny. Wiggling the leads it drops to 325 on the lowest with 2.5 mv offset. 700 mv on the highest setting with 3mv offset. I'm changing out the bias tranny.

 

[Gepetto]

I use all 75 ohm cables Lee, RG59/U

 

[laatsch55]

Yes Joe, this is the right channel. Behaving as it should?? Did you see the THD & N figures for this channel??

 

[laatsch55]

I use all 75 ohm cables Lee, RG59/U

Naturally.....

 

[laatsch55]

With no inputs or outputs plugged in offset goes to 12mv.

 

[Gepetto]

Yes Joe, this is the right channel. Behaving as it should?? Did you see the THD & N figures for this channel??

Hi Lee
You will note I said "at least in this regard"

Yes I saw the hump in the THD that climbs to ~20%

 

[Gepetto]

With no inputs or outputs plugged in offset goes to 12mv.

Negative 12mV? It should be negative (NPN input stage). I typically see -0.010V

 

[Gepetto]

Naturally.....

RG59/U is very common for BNC connected cables.

 

[laatsch55]

Negative 12mV? It should be negative (NPN input stage). I typically see -0.010V

Yes-12 Joe, sorry, I'll start noting that. Bias tranny changed out. Still not the range I would like to see..460 as the lowest.

 

[laatsch55]

RG59/U is very common for BNC connected cables.

Front panel on the AP has XLR or banana.

 

[laatsch55]

Joe, be back in 30 min. Gotta run down to the shop and load some shit out for an early morning pumping unit fix...

 

[laatsch55]

The .33's are metal oxide

 

[Gepetto]

Thats a good thing Lee. Great for this application.

 

[laatsch55]

Those are the ones that are in there. Had to check my order history at Mouser and check for sure. Iwas pretty certain I had bought MO's.

 

[Gepetto]

Did you get the right channel settled down yet Lee?

 

[laatsch55]

No Joe I haven't. Took a break. Ken nelson's 400 did not arrive in good shape. The meter holddown allen head 6-32 machine screws came loose and fell against various locations on the backwall and he plugged it in.

So Lickety Split got back here 2 days ago and I finally opened her up last night-------you would not believe the damage that resulted....

 

[laatsch55]

The lightboard powered up, but nothing else........then the biggie....