700/1 “Tim” WOPL driver board

[AngrySailor]

As well you should, when messing with the original backplanes that's a win bud!!

Thanks Lee, couldn’t have done it without all the help here.

 

[laatsch55]

That's why we're here, for stuff just like this!!

 

[AngrySailor]

Cut out the bad, in with the good, tap tap tap make straight... buddy Trever doing a heck of a job saving these old fenders... he’s working for beer so far too!

 

[laatsch55]

Poor guy doesn't have much to work with sometimes....

 

[AngrySailor]

Poor guy doesn't have much to work with sometimes....

He’s already made a new patch for there. These fenders are near 100 years old, this one is the worse of the pair. Make him start with the nasty one!

 

[Gepetto]

Practice makes perfect guess I’m getting lots! Hopefully got it licked. Might take a break for a bit maybe the night. Gotta put the DCP back in and connect the meters and light board too. Made a real brain fart there forgetting the negative rail supply, also got the wrong bias resistors... see how long these hold up!

Unless something goes haywire, the bias resistors only have 13milliwatts dissipation. With a 1/4W resistor in there you have 20x safety margin

 

[AngrySailor]

Unless something goes haywire, the bias resistors only have 13milliwatts dissipation. With a 1/4W resistor in there you have 20x safety margin

Well with how I treat the loud knob sometimes “haywire” isn’t exactly off the table!

 

[laatsch55]

LOL!!!!

 

[AngrySailor]

Almost back together. Passes bench tests, idled for half hour or so then set bias to 350mV. Going to close things up and give a listen but I have to inspect a crossover in my right side 3 way cabinet first. Something wonky and it’s remains in the right cabinet after swapping amps, pre amps, signal paths left to right and even swapped the drivers left to right. The passive crossover is all that remains common to this problem...

 

[laatsch55]

Looking good Andrew...

 

[Gepetto]

Almost back together. Passes bench tests, idled for half hour or so then set bias to 350mV. Going to close things up and give a listen but I have to inspect a crossover in my right side 3 way cabinet first. Something wonky and it’s remains in the right cabinet after swapping amps, pre amps, signal paths left to right and even swapped the drivers left to right. The passive crossover is all that remains common to this problem...

You have too many Zoebels Andrew...

 

[AngrySailor]

You have too many Zoebels Andrew...

Just looking at how to remove the one from the light board. If I remove the two 10 ohm resistors and the cap, the signal path through the meters will be open...

 

[Gepetto]

Also trying to figure out what you are measuring with your DMM?

 

[AngrySailor]

Found my crunch noise from the right cabinet. Broken lead in my crossover...

 

[Gepetto]

Just looking at how to remove the one from the light board. If I remove the two 10 ohm resistors and the cap, the signal path through the meters will be open...

Shouldn't be, just remove the caps, that will open the Zoebel

 

[AngrySailor]

Also trying to figure out what you are measuring with your DMM?

Bias? Base on the + rail to the speaker output no? That’s the collector bus bar on the negative side? I get the same reading across the bias resistor or the test points on the board? Am I making a big dummy move here? (Wouldn’t be the first time...)

 

[Gepetto]

Bias? Base on the + rail to the speaker output no? That’s the collector bus bar on the negative side? I get the same reading across the bias resistor or the test points on the board? Am I making a big dummy move here? (Wouldn’t be the first time...)

There is a yellow test point for that on the upper edge of the control board. You are reading 0.002V of bias.

 

[AngrySailor]

There is a yellow test point for that on the upper edge of the control board. You are reading 0.002V of bias.

Oh fug, the amp is off in that pic Joe. Want me to test again on? When using the test point, I don’t check to ground do I? Was 350mV both channels. Also, I just removed the caps from the light board.
Damn, forklift being dropped off for repair. BRB.

 

[Gepetto]

Oh fug, the amp is off in that pic Joe. Want me to test again on? When using the test point, I don’t check to ground do I? Was 350mV both channels. Also, I just removed the caps from the light board.
Damn, forklift being dropped off for repair. BRB.

If your output offset is zero, which it is if the amp is working properly, you use the black ground test point on the top edge of the board for your negative DMM lead and the yellow bias test point for your positive DMM lead.

I try to make it convenient so that there is less chance of making a bad move with your test clips and accidentally blowing something up.

 

[laatsch55]

Oh fug, the amp is off in that pic Joe. Want me to test again on? When using the test point, I don’t check to ground do I? Was 350mV both channels. Also, I just removed the caps from the light board.
Damn, forklift being dropped off for repair. BRB.

The xoebel.components are in.parallel with the meter drive. Removing them should have no effect on meter operation.