Larry's Phase Linear 700B

[jbeckva]

Nav, the pot was suspect and something I hadn't isolated yet.
Jer, input impedence or DC offset??

Input impedance.. power off of course...

See if there's a diff in resistance with no rcas plugged into the suspect channel. If there is.. then it's prob in the circuit somewhere. If not, plug the rca into the suspect channel but leave the other end unplugged and then recheck.

 

[laatsch55]

OK, that makes sense, but input impedence is not a static measurement is it? I always thought it was active.

 

[laatsch55]

32K on each plugged in or not./ After turning on the amp to check some more R51 on the LED board started smoking. Joe--- WTF??

 

[laatsch55]

Each pot starts at 32k and goes up in resistance as you turn them down.

 

[jbeckva]

OK, that makes sense, but input impedence is not a static measurement is it? I always thought it was active.

Sure is, but I am usually thinking one thing and saying another.. heheh. The idear was to do a quick check first for anything "obvious" where a drastic drop in resistance from the norm would be easily isolated.

But.. hmm.. the LED board has a resistor giving up the ghost now???

Sir, you need a priest and holy water.. were you playing black sabbath backwards at Mach 10???
(just kiddin... couldn't help myself there.. hmmmmm... what could it be??)

 

[laatsch55]

R51 on the LED board will smoke if Q1 is not in circuit...JEEZ....................

 

[laatsch55]

Really snake bit on this one, self-snake-bit is always better.

 

[laatsch55]

At 200hz all the way up to 500watts per channel we have less than a 1/2 watt difference in level, loaded with 8 ohms. No, I did not try a level test without Q1 in circuit last night when i was getting the funny input readings, don't know what happened. Something loose in the pot??

 

[laatsch55]

10K up to 500 1 watt difference.

 

[orange]

WOW, That sounds cranky. Did you try a Tuck's pad on the output?

 

[laatsch55]

At 20Khz 3 watts different at 500watts output. No diff3erence when driving channel A or channel b together or alone.

 

[laatsch55]

Not yet Steve.

 

[laatsch55]

Doug---it's going on the horns for THE listening test. If it sounds as good as it looks on the AP, it's getting shipped tomorrow also. I have not relocated the AC power in. If there is no audible hum no reason to anyway. We'll see in about 20 minuts.

 

[jbeckva]

So what was the issue? Q1?

 

[laatsch55]

Doug's 700 on the horns , the Carver 2400 on the Soni's, getting physical in here!!!

 

[laatsch55]

So what was the issue? Q1?

Yep.

 

[laatsch55]

Doug, we have hum. The 60Hz kind. Gotta fix it.

 

[orange]

Ah, hell...have fun first. AUTO-TUNE it.

 

[laatsch55]

Oh we are Steve. It's getting quite a workout.

 

[fitz43]

ok, I have been following your updates. thanks.