Jerry's "Gonna Rebuild me PLWO 1000" thread

[speakerman1]

You probably thought I was stupid to ask what size washers. Is it a reg. washer or a large area washer. That is what I meant by size.

Larry

 

[jbeckva]

Not at all.. I just premounted the trannies this time... worked a lot better. We don't need to steenkin wachers, mon... heheh

Got the other side in with the collector buss attached. Still a pluggin...

 

[laatsch55]

Can achieve even better results with the proper ground plane return associated with the signal or voltage plane. It can be worked out. The biggest challenge quite frankly is mechanical. Not sure that Phase Linear adhered to exactly the same layout in every amp vintage.

So if I run the 4218's in the monster, can they be mounted to a PCB that would also tie to the heatsinks??

 

[jbeckva]

Ok, right channel is done...

A few learnt-lessons.. superglue the sockets with just a lil tiny smear first, then everything is guaranteed to line up. Don't overdo the solder on the base and emitter pins, or it could go down and close the pins themselves. Measure off one leg of any buss, then cut the rest to size and preposition all before soldering. Some socket screws are shorter than the others... heheh.

Anywhoo.. time to start tearing down the left channel. Also.. on the AC plug.. was it Joe saying it's not a good idea to do a three prong/grounded plug? Why isn't it? The transformer primary is isolated, and the main ground is all based on the center tap off the secondary. Shouldn't it all be at the same voltage potential, or no?

 

[laatsch55]

Lot of work ain't it Jer. Ed Blackwood tells me the gals that did most of the amp building could do 2 a day. I'll see if I can find that post of Joe's.

 

[jbeckva]

Two a day?? Whoa...

Well, I think I got better already... since the last post, here's the progress.. Left side's ready to re-populate!

I'm getting me groove, I think... hehe.

 

[jbeckva]

"Wired by Dart" ??... now it will be "Wired by Dude"...

 

[laatsch55]

LMAO!!!!

 

[wattsabundant]

It looks like the relay board has been mounted to the chassis. The board has the Zobel network on it. So if I interpret the picture right the parallel resistors should be removed. If the chassis hasn't been drilled out switching back to the original binding posts would make this a lot easier. Think long and hard before drilling out the holes on the board as they're plated through and spacing of tracks near the binding posts assumes the 4-40 post are used.

 

[mlucitt]

I'll let Lee chime in here but yes, you can remove the parallel resistors. I used the nuts on the binding posts to hold the board in place and the fit was good. I could have soldered the board in place, but removing it later would be a real PITA.

 

[laatsch55]

Jer and I had discussed the duplicate "Zoebel" before. It goes. This amp got new aftermarket binding posts so the board would not quite line up. Maybe with some offset standoffs it could happen. That's why you see the board mounted to the side. This was White Oaked before Don came out with his DC board. This is the one with the AmpsLabs Dc board.

 

[jbeckva]

What about that 3 prong AC main idear? Not yet "there" but I'd like to get some feedback on why or why it aint a good thing.

Almost done with the positive rail on the left channel.. we're truckin' still..

 

[jbeckva]

One more for you guys... this Z network... I'd assume that it's a type of low pass RC circuit that would catch high frequency stuff and shunt it to ground, right? So with 2 10 ohm resistors in parallel (5 ohms eh?) and .1uf's of capacitance in series, what would the slope and -3db/-6db points look like?

I should probably know this, but it's been like ... 23 years since. Never had the need to know it either, but now I'm just curious and filling in the blanks..

 

[laatsch55]

It protects the amp if it gets connected to a highly reactive or inductive load, think current sink and shunt.

 

[jbeckva]

Ahh ok.. but still if it was used in a xover and with the resistance and capacitance presented in parallel with the load, what might the frequency points be?

(brains fried tonight.. done with the positive rail, but too tired to go into the "she-bear" cave and get the camera... hehe)

 

[laatsch55]

Don't know Jer. Not a crossover man.

 

[jbeckva]

You're going to make me go look it up, aren't you?

naaaah.. tomorrow.. toob n vegout time...

 

[laatsch55]

No tunes and rework??????????????????????????????????

 

[mlucitt]

Found this:
A boucherot cell (or Zobel network) is an electronic filter, used in audio amplifiers to damp high frequency oscillations that might occur in the absence of loads at high frequencies. Named after Paul Boucherot a boucherot cell typically consists of a resistor and capacitor in series, that is usually placed across a load, for stability.

It is commonly seen in analog power amplifiers at the output of the driver stage, just before the output inductor. The speaker coil inductance of a loudspeaker generates a rising impedance which is worsened by the output inductor generally found in analog power amplifiers; the cell is used to limit this impedance.

The documentation for some power operation amplifiers suggests the use of a "boucherot cell between outputs and ground or across the load"

It would be a first order RC network so approx 6db is close enough and the cuttoff frequency is 318 Khz for the parallel 10 Ohm resistors (total resistance 5 Ohms at 4W) and a .1 uF capacitor.

 

[jbeckva]

And, here we have both channels done. Prolly downhill going from here. Whew... Hey Lee.. ya gots another one ya need refurbbied?? (or do you wanna see me power this up first without losing any magic blue smoke??)