Phase Linear 400 Amplifier Upgrade to WOPL

[NavLinear]

Know all about it, old farm kid here. Pulling calves out of heifers bred to young, 20 below, middle of the night, and no one happy about what is going on, cow, calf or calf puller.

We have cows with calves - even the middle of the night with no one happy but what does 20 below mean?



Couldn't resist.

 

[laatsch55]

We have cows with calves - even the middle of the night with no one happy but what does 20 below mean?



Couldn't resist.

Something you would find very foreign. The thermometer actually goes below zero out here. And if you resist you will spontaneously combust.

 

[NavLinear]

Ok - finally. I did not have my thumb up my a33 - really! Here are a some photos of the new controller board without the transistor heat sinks but with some wires attached. I really like the MIL-W-22759/xx wire. It can take the heat and is flexable so moving the board is not problematic. I beleive that the wire I came up with is 200 degree C wire. I didn't find a white/black/green wire in 22 AWG but I did find a white/black wire so that's what I use for the multi color wire.

I've been doing some testing on the almost unmodified PL 400 (the WO cap kit is installed) but the results are at work. I should get those posted tomorrow.

 

[NavLinear]

I had to add a new AC plug to my variac so I've included a photo of this to bore everyone along with a couple more photos of the WO controller board.

 

[NavLinear]

I'm hoping to get a reasonable baseline of the before and after but (big butt) as this will be my first audio amplifier upgrade and the HP 8903A is a new toy - my first tests will not include data from the audio analyzer. No worries though as I've been dicking with it for some time. I used my trusty HP3325A Synthesizer/Function Generator, Fluke 8840A Multimeters and Tektronix 2445 O'scope. I do have a spectrum analyzer and other test equipment at my disposal so those will be used when necessary.

More to come - damn - wish I brought home the data!

 

[NavLinear]

Oh - forgot to mention that a prototype bias transistor bracket is in the works - soon to be in the oven so to speak. I'll keep you posted.

 

[NavLinear]

So far all my testing has been with an unloaded system. Tomorrow we'll get loaded - the amp that is!

 

[laatsch55]

Dude I know where you can get more knobs for your variac.

 

[laatsch55]

200 Deg wire doesn't even melt back on soldering does it?/

 

[laatsch55]

Your board work is gorgeous Dennis, wayyyyyy nice.

 

[NavLinear]

200 Deg wire doesn't even melt back on soldering does it?/

No it doesn't. You can see some discorloration in the insulation (tends to darken) while soldering but when it cools the color is back to normal. I've used this wire type for years and it has worked well in many applications from high heat to well below -40 degrees C.

 

[laatsch55]

Where have you seen 40 below???????

 

[NavLinear]

Where have you seen 40 below???????

Not meeeeeee! Some of the hardware I work with sees way cold temperatures at way high altitudes going way fast.

 

[laatsch55]

Oh, sounded like you were watching it turn cold!!! It's been so cold here that taking a piss it was ice by the time it hit the ground.

 

[NavLinear]

In another thread there was some discussion about bleed resistors - aka cap zappers. I thought I'd share with y'all what I built as I can hook this up without fear of arcing as the fingers are well away from the cap when the switch is thrown.

I used a three position switch and installed two ten watt resistors in a small Pomona box. I also installed a couple of pin jacks so after the fact I can look at the voltage - just to be sure. I went with banana plugs on the lead ends so different clip styles can be used based on what your clipping on to.

I'll clip one lead onto the cap that I want to bleed and and the other to a ground point with the switch in the open position - get a little distance between fingers and capacitors, then flip the switch and measure the voltage after a second or three. I normally use the 50 ohm resistor. So far the Cap Zap has worked out well and it was a fun little project.

 

[NavLinear]

Something else that has been in the works for a while is a bias transistor bracket. What I wanted was something that was simple to install and would protect the legs of the transistor and provide a tie point to secure the wires that attach to the transistor legs as these wires are flexed when the controller board is moved for testing or other modifications. I incorporated the fastener (4-40 nut) in the bracket to make the assembly a little easier.

The 400 uses 4-40 screws - what about the 700? Since the fastener is part of the bracket design a larger screw would require a minor design change to accommodate the fastener.

I'll get some more photos tomorrow with wires attached to give a clearer picture of this. The first two photos are of the bracket and fastener and the last three have the transistor included.

 

[laatsch55]

700 uses the same. Dude does that mind of yours ever shut off?? That's some cool shit there Dennis, the cap zapper is great. Love the ability to use different ends, because one size does not fit all!!

 

[laatsch55]

Now I can make the connection between the 20 and 50 ohm resistors and the small Pomona boxes from 3 goody boxes ago, very devious Dude!!

 

[mlucitt]

A little neon light with a load resistor would be cool if it would light up as the cap bleeds down and then go off below say 10V.

 

[laatsch55]

It's all over in 3 seconds or less anyway.