The ultimate dual 500 "rising from the ashes" build

[Steve crane]

First step is take it apart. If any one knows how Phase linear Serial numbers work please pipe in

This unit is 1002. I am making up that it is #2 built. She is named Val

That's are many parts with date codes from 1977. The control boards are consecutive part numbers.

Here is some history on the 500

http://www.phaselinearhistory.stereomanuals.com/d500amp.htm

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[Steve crane]

Serial numbers start at 1000 but the first dual 500 I own, bought it at the factory still have it today is numbered 1501,it was the amp that debut the dual 500 at stereo show in las Vegas, there were three of these original amps the other ones debuted did Detroit show and the Europe show and the one in the Europe show never came back to be numbered, the first 500 amps went out the door before they actually came back from the show so they were numbered 1501 and 1502

 

[Steve crane]

So i guess yours is really number 5 or 6 if you want to count the one they used inside the factory never numbered either

 

[Steve crane]

Today update
replaced power caps with matched 15,000 uf ones
replaced Zobel resistors both channels

After about 10-15 minuets under light load ( warming things up)

left channel running only 5 volts output

.132 mv at 1.2k input

N+THD .08%

initial warm Bias .3mv at 75volt both channels

8ohm load connected on driven left channel only (the problem child )

rail at 75v with 150v across caps ( low z setting)

no heat in heatsinks (80-90'F)

sitting and sipping a cup of tea and as I watch the unit do the following observation

Slight voltage drop in room ( slight loading sound)

Suddenly both vu meters rise( only one driven) to about -10 db on meters then driven left chann neg Rail fuse blows (only have 4 amp at this time as s little caution and last time the positive fuse blew)

rail voltage steady at 150v

blown driven Chan had minimal bias mv on left chann with right channel still at .310mv after fuse blew

turned off and now scratching my head

question what caused both channels to show high output on meters

did not have scope in sight when happened.

Something suddenly drove both channel with only one input connected
left channel is one blowing fuses wether under load or not.
Rise in output to excead the 4 amp fuse on loaded channel is obviously the case for fuse going out this time

unloaded channel into no load did not pass enough current to blow fuses yet this channel was suddenly driven

the indecent was not fast as it took about one second to rise and blow

are we any wiser ??

ideas anyone

Sounds like something mine just did even the gains were all down,blew me out,dove for the power button,turned back on did it again turned off the high frequency light stayed on turned on few mins later seems fine i idk

 

[Steve crane]

Sounds like something mine just did even the gains were all down,blew me out,dove for the power button,turned back on did it again turned off the high frequency light stayed on turned on few mins later seems fine i idk

So what was the exact problem causing the distortion,was it a bad solder job back by the RCA jacks?