Russ' Phase Linear 700B Going Fully Comp!!!!!!!

[laatsch55]

81.2 volts on the rail at full rated output....

 

[NavLinear]

81.2 volts on the rail at full rated output....

That seems low - what are the rails measuring before loading? Mucho droop'o.

 

[NavLinear]

THD & N unweighted....

Something is still amiss - any ideas?

 

[laatsch55]

104.2 unloaded. THD & N is a mystery as is residual noise. From my perspective of having my ear in the horn and barely hearing anything I'm measuring 1.2 and 1.3 MV of residual. It doesn't SOUND like what it measures..

I'm going (just for shits and giggles) to drop R34 back to the eriginal value and see what effect that has, plus as soon as Joe gets his running we'll be doing some comparisons I hope.

 

[laatsch55]

Something is dragging the power supply down. I have Stephens 700 still here tha is stock. I may measure the voltage sag on that puppy as I don't remember doing that to a stocker either...

 

[jbeckva]

Something is dragging the power supply down. I have Stephens 700 still here tha is stock. I may measure the voltage sag on that puppy as I don't remember doing that to a stocker either...

Got another BR to swap in?

 

[laatsch55]

Yes I do Jer!! Why has that been naggin at the back of my mind? Well, what's left of it...

 

[laatsch55]

Can they leak and not short?

 

[laatsch55]

Factory 700....92 volts at 512 watts output...residual 789microvolts and 1.09 milivolts..

 

[laatsch55]

OK Joe, changes made, any tests you want run?

 

[Skratch]

81.2 volts on the rail at full rated output....

The 700 power transformer may be running out of gas as it is rated at 960 watts?

 

[laatsch55]

Mark, I don't know exactly what the KVA rating of the original is.But this will be the lwest testing 700 we've done at 416 before clip, and that ain't right, I think Jer may be right, I did have a short to the case on that BR, and I don't know if you can have a leaky BR that doesn't short but can drain significant current, that's my question of the day..

 

[Gepetto]

Mark, I don't know exactly what the KVA rating of the original is.But this will be the lwest testing 700 we've done at 416 before clip, and that ain't right, I think Jer may be right, I did have a short to the case on that BR, and I don't know if you can have a leaky BR that doesn't short but can drain significant current, that's my question of the day..

Or your caps aren't what you think they are. It is important to look at the minimum valley voltage on the rail when you are loading the amp. The time in between AC charging peaks that occur every 8.3msec, the B+ and B- supply voltage is held up by the energy stored in the cap during the charging peak. That is the caps responsibility. If it is decaying too much in this time duration, you will see lower average bulk voltage. This will show up on a scope shot of the rails, with the scope AC synched.

 

[laatsch55]

Hookay, how do I set up the scope?

 

[Gepetto]

Hookay, how do I set up the scope?

Scope ground to the bus bar, scope tip to either the B+ or B- supply. On your scope trigger menu you will have options like CH1, CH2, CH3, CH4, Ext, Ext/5, AC Line. Choose the last one and the scope will synch perfectly to the AC line peaks.

On the Channel menu, choose AC coupling and set your 20MHz Bandwidth limit to ON. Setting on AC will allow you to set your sensitivity at around 2V/Div to get good resolution on what you are looking at.

 

[laatsch55]

What am I looking at?

 

[Gepetto]

What am I looking at?

I will skip the smartass reply Lee

You are looking at either the B+ or B- rail voltage. You normally are citing what meter reading you are getting. This is asking you to look under the covers with the scope.

 

[Gepetto]

What am I looking at?

Should be a trace that looks something like the yellow trace in this picture.

 

[Northwinds]

Could it not just be a weaker transformer then what your accustomed to seeing in these?

 

[laatsch55]

Ok, on channel 1 I have AC coupling, 20mhz limiting ON..