School me on the PL Pro 700

I guess the guys a PL thought so too. The original caps are 0.047uf ceramic. Perfect.
 
If yuou have polypro and Mica to sub out the ceramics, that helps too...
 
So there is this post

By the way, there is a simple modification Dean showed me a few years ago that dramatically reduces the total harmonic distortion to levels as low as that of the 300 II. If my memory serves me correct it is in relocating C106 and C206. If you compare the Phase Linear 300II schematic with the 400II and 700II PL-36 pc board schematic you may be able to figure out where the capacitor locations are different. The (rare) PRO700 schematic I believe has this illustrated. The PRO 700 pc boards I have seen were drilled with an extra set of holes next to the 40412V1 transistor for relocating this capacitor.
Click to expand...

With respect to Ed's suggestion on the feedback cap, remove C 106 and tack a 56pf cap in parallel with R119 (12k, 1/2W). The 120pf C106 could be used but it may affect high frequency response.
Click to expand...


On my 700 Pro, the C106 as illustrated on the schematic does not exist. It is already installed in a set of holes that are parallel to R119. Its a 120pf capacitor.
 
Thats the one with the big square heat sink? If so, yes. Both sets of holes are there actually. The one in use is parallel to the resistor, the one not in use matches up with the schematic. They are physically on opposite sides of the resistor. With the cap in parallel, it is closer to the heat sink. To match the schematic, its away from the heat sink.
 
Are the pads on the foil side going to different places?
 
Yes. The side closer to the heat sink parallels R119. The side away from the heat sink connects one leg of R119 to the bias pot. I'll see if I can get clear pics of it tomorrow. I shut it for the night and was listening to some Deep Purple.
 
The connection Ed was referring to IIRC, cause Ed and I have talked about it a couple times, the cap went to the base, collector points...
 
P.L.F. said:
The redrawn ones, most updated that I sent you, illustrate already the C106 @ 120pf...
Click to expand...

They do, however they do not show the capacitor where it is installed on my unit. The location shown in the updated schematic is the same as the stock original PL36 board, and the PL36 board set up for complimentary operation. My Pro board has the capacitor across R119. The holes do exist to put the capacitor in the location drawn on the schematic as well, however there were no signs that it was ever there.
 
laatsch55 said:
Not uncommon in production runs..
Click to expand...

Some pics of the caps in question. I changed it out to a silver mica, but it is re-installed into the hole it came from. The yellow jobbers are 0.047uf to replace the ceramics. Vastly overkill at 630v, but its what I had around. The 500v SM caps are there for the same reason. This low voltage stuff is strange stuff indeed.



resized_PL36_pro_topview.jpgresized_PL36_pro_C206_topview.jpgresized_PL36_pro_C206_botview.jpgresized_PL36_pro_C106_location.jpgresized_PL36_pro_C106_botview.jpg


Also set the bias while I was in there. One side was running about 200mv, the other read nothing until I bumped the pot, then it came up to 180mv. Sounds happier at 360mv.
 
380-385 is ideal... good job of shoehornin' em in there...
 
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