White Oak/ Phase Linear Troubleshooting Guide

[mlucitt]

Lee, what was the indication that made you say you lost bias on one of the channels? I'm thinking that we could put together a pretty good troubleshooting guide based on our experiences. Using the military approach of 1) checking for good input, 2) verifying bad/no output, 3) selecting a point halfway through the circuit and checking for signal, 4) if found, move downstream halfway again, if not found, move back upstream halfway until found, etc. Separate section for PS issues, and bias and protection issues. Joe's boards are good enough that we could put some voltage readings at selected critical points (with Joe's approval, of course) on a known good board to make voltage checks. Then, if the voltage is low/high go "here" or replace "part" and we could have a consistent set-up (maybe using your ATS-1 parameters) like 1kHz .5V sine wave input, 8 Ohm load on output, etc.

Maybe that is a new thread?

Mark

 

[NavLinear]

Lee, what was the indication that made you say you lost bias on one of the channels? I'm thinking that we could put together a pretty good troubleshooting guide based on our experiences. Using the military approach of 1) checking for good input, 2) verifying bad/no output, 3) selecting a point halfway through the circuit and checking for signal, 4) if found, move downstream halfway again, if not found, move back upstream halfway until found, etc. Separate section for PS issues, and bias and protection issues. Joe's boards are good enough that we could put some voltage readings at selected critical points (with Joe's approval, of course) on a known good board to make voltage checks. Then, if the voltage is low/high go "here" or replace "part" and we could have a consistent set-up (maybe using your ATS-1 parameters) like 1kHz .5V sine wave input, 8 Ohm load on output, etc.

Maybe that is a new thread?

Mark

This is a great idea Mark. Were you thinking of doing this in a thread format and making it a sticky or going down the path of documenting it on "paper", reviewing it and than posting sections / chapters / or?? in a pdf format? It really doesn't matter - just the content would be invaluable.

Certainly first on the list is to be careful where you put your probe.

 

[mlucitt]

Agreed, it is so easy to slip off a contact point when you lean over to glance at the meter or scope when the unit is energized. Based on the amount of rework I've done, now I will shut down, hook in, and then power up. It takes longer but not as long as troubleshooting and then replacing several components that have let their smoke out because you just caused a momentary 100A current path through them to ground.

By having the voltage test points (TPs), it would be easier to troubleshoot those items that tend to fail internally like transistors and diodes. A simple reading on the collector for example can often tell if the transistor is conducting or turned off, depending on the role of the device and the state that it should be in. Most often, when resistors fail there is a burning evolution and cap failure is almost always a messy and loud event. I try and compare Left and Right but sometimes I'm not sure what I'm reading is a "good" signal/voltage.

Mark

 

[laatsch55]

Troubleshooting Scenario #1, Lights power up, no DC relay click, 15.56 volts DC on th

Here's one for ya sportsfans. ............
An amp was shipped (in the cabbage case even) and when it got there 3 out of the 4 meter hold down allenheads had made their way into the busbars on the backwall on Ken's 400, Lickety Split. Then he plugged it in. No smoke, no fire, no blown fuses, no outputs blown, no drivers blown, no pre-drivers blown, not one diode blown, NOT ONE SEMICONDUCTOR took a hit. Dc protect was holding out the output signal. 15.56 volts DC on the speaker outs. Then after poking here ands there I managed to get the Dc on the outputs up to 80 volts----ah---nothing like progress---. After almost tearing out what was left of my hair I decided to check EVERY FUCKING RESISTOR ON THE BOARD. EVERY FUCKING SEMICONDUCTOR TESTED GOOD!!!!!!! In circuit AND OUT!! Guess what resistor??? R2L, R2R, yep the easiest to get to, that ain't right. Replaced R2L, and R2R and things were great, DC offset was down to -.002 ands -.004. Bias was rock stedy where ever you put it. Hooked it up just now, and anything above a couple watts sends the Dc protect into a tizzy shutting down the left channel. Severely distorted. I would guess Q1-Q4 took some of the hit. They checked as well as the rest, guess the static tests don't tell all. This is the first time I've seen resistors go before ANYTHING else, even a fuse. Stay tuned, going back in.......................

 

[mlucitt]

Lee,
I've had this problem of loose meter hold down clamps as well. Caused by not torquing down on the meter hold down clamps too much because they often cause the meter to bind when the plastic case is tweaked beyond a certain point. I may be age or who knows what. Here is my suggestion for a fix:

Insert the screws and hold down clamps as usual, finger tight at this point. Wiggle the meter in the face plate bracket to ensure it is firmly locked into the bracket, make sure the end of the hold down clamp is set into the slot in the meter. Tighten the screws again - finger tight. Repeat this procedure until the meter is firmly in place and all the slack is out of the hold down clamp and clamp screws. Put a small piece of tape across the clamp and meter to keep it in place in case the hold down clamp comes loose. Then put a drop of clear nail polish or Loctite on the screw threads.

Good Luck,
Mark

 

[fitz43]

Lee,
I've had this problem of loose meter hold down clamps as well. Caused by not torquing down on the meter hold down clamps too much because they often cause the meter to bind when the plastic case is tweaked beyond a certain point. I may be age or who knows what. Here is my suggestion for a fix:

Insert the screws and hold down clamps as usual, finger tight at this point. Wiggle the meter in the face plate bracket to ensure it is firmly locked into the bracket, make sure the end of the hold down clamp is set into the slot in the meter. Tighten the screws again - finger tight. Repeat this procedure until the meter is firmly in place and all the slack is out of the hold down clamp and clamp screws. Put a small piece of tape across the clamp and meter to keep it in place in case the hold down clamp comes loose. Then put a drop of clear nail polish or Loctite on the screw threads.

Good Luck,
Mark

or a jam nut on the clamp screw between the clamp and the head of the screw.

 

[laatsch55]

or a jam nut on the clamp screw between the clamp and the head of the screw.

Great minds think alike!

That will keep the hold down screw in place, but the meter still needs to be stabilized, cause if yiu tighten it enough to keep it there in shipping it's too tight to work right`. so silicon like the factory did is my preferred option right now.

 

[Gepetto]

I always put a dab of clear silicone on the end of the screw that touches the back of the faceplate as well as where the clamp touches the meter back and at the junction of the meter clamp bar and the threads. I also put a thin bead on the meter sides to glue the meter to the faceplate.

Those clamps are useless.

 

[laatsch55]

On a recently finished 700 Ser I with the White Oak Rev C board. Initial complaint was low power on right channel, sounding worse as you turned it up. This was relatively easy. No outputs or drivers shorted or open, got some weird readings off the 1N4004 diodes accross the backwall. Sure enough one was open. Replaced and everything was back to normal until a slip of the probe while powered up. Had I kept a good log on the ensuing 30 days of trying everything in my power to screw this amp up , our troubleshooting section would be nearly complete.

The last screwup was showing a bad upperhalf of the sinewave on any loaded signal above 3KHZ. After driving myself crazy for a good two weeks, I finally saw I had put two small caps in the wrong place. I had reversed the placem,ent for C10R and C18R. A very bad thing to do. No coll;ateral damage but I sure chased my tail and replaced a LOT OF PARTS. I'd show ya the pile of parts but it's too embarrassing.....

 

[NavLinear]

I'd show ya the pile of parts but it's too embarrassing

Just think of it as honing your parts removal and soldering skills.

You got it fixed - that's what counts!!!!!!!!!!

 

[laatsch55]

Dude!!! I have a world class solder sucker and Dad taught me to solder before I could walk, what I DO NOT NEED is more practice. I will post a pic of the parts pile though.....

 

[NavLinear]

I'm sure you have some great stories about your dad - being a high flyer - got to work with a few in years past. Always good people.

 

[laatsch55]

When they weren't being good they were mostly insane..... On my 12th birthday, saw him singlehandedly take down 6 of Riversides finest, with his bare hands. Knocked 4 of em plumb out, #'s 5 and 6 were a wee bit groggy when they pulled their fire sticks out and asked him to get in the car. I heard him yell that that's all they had to do in the first plce was to "ask" him to get in the car, but if they insisted on ordering him to get in they just as well plan on pullin them triggers and hope ta god that's enough to stop me before I get to ya." Yeah, he was that tough, he's been dead since 85, and I still wouldn't mess with im.

 

[NavLinear]

When they weren't being good they were mostly insane..... On my 12th birthday, saw him singlehandedly take down 6 of Riversides finest, with his bare hands. Knocked 4 of em plumb out, #'s 5 and 6 were a wee bit groggy when they pulled their fire sticks out and asked him to get in the car. I heard him yell that that's all they had to do in the first plce was to "ask" him to get in the car, but if they insisted on ordering him to get in they just as well plan on pullin them triggers and hope ta god that's enough to stop me before I get to ya." Yeah, he was that tough, he's been dead since 85, and I still wouldn't mess with im.

Damn - I wouldn't want to f##k with your dad either. It sounds like he was a big guy and flying one of those Blackbirds took a lot of balls. With very few exceptions all the fighter and high flyer pilots I've known were way cool.

Ok - time for a quick story of mine that I heard about while working with some Air Force weenies (I was not there!):

One of the groups that I worked with for over ten years - I was a Navy puke - would have some crazy late night parties into the wee hours of the night during work nights. Of course I'd attend - couldn't help myself. One night an officer (won't say names) got drunk and passed out - big surprise there and nothing abnormal for these guys. Well - some of the guys broke into the base "hospital" and hauled the passed out captain in one of the rooms and hoisted him onto a table. They broke out the plaster of paris casting material, partially stripped him and put him in a full body cast! The next day was waaaaaaaaaaaay funny. Some may have been punished for this act but I didn't know anything. I'll deny it to my grave!

Did I say this outloud?

 

[laatsch55]

Nav, he had arms like my legs. As I was growing up I'd get ta thinkin I outta try im. But one look in his eyes and that idea passed.....Like lookin in a snakes eyes, you're just prey....

 

[laatsch55]

The services were full of pranksters.

He did give me some advice on the Navy types, and this is a quote---" Son, if you are ever in a ten mile radius of a Masterchief take time to go shake his hand as they are some of the finest men walkin the face of the earth."


Me thinks they fished him outta the drink a few times...

 

[NavLinear]

The services were full of pranksters.

He did give me some advice on the Navy types, and this is a quote---" Son, if you are ever in a ten mile radius of a Masterchief take time to go shake his hand as they are some of the finest men walkin the face of the earth."


Me thinks they fished him outta the drink a few times...

I've known a few in my days - the stories would make you - well I'm not sure what they would do but some of 'em are f##king funny. Can't go there but..... just thinking about some of the stuff cracks me up!

 

[laatsch55]

B+, B- voltage on the speaker outputs.

Had a couple instances lately where i had rail voltage on the speaker outs. What should have been the first thing to check after checking for shorted outputs was to check for +20, and -20 coming out of the low voltage regulators. Without one or both. nothing is turned on in the input section and rail voltage goes directly to speaker posts.....

 

[Gepetto]

By the way, it takes a double fault in the regulator for that to happen.

The +/- 20V regulators are protected against a single fault in the circuit design. The only thing that it cannot protect against is a short circuit on the output of the + or - 20V regulator.

 

[laatsch55]

Damn, you're good. That's exactly what happened!!