David's Phase Linear 700B Thread

[jbeckva]

Just what I wanted to hear. Wonderful. If re-running the AC wire path is in your time-process.....have at it! This will make one powerful low end amp. Once you send it back Jer, I will send you my other 700B that I use bi-amped for my high end! You can WOA that all the way! It's even more cosmetically beautiful than the first one? So can I consider this one a WOPL 1000 yet?

Sure sounds like one, David. I think Joe really hit a stride with the "D" rev's - I think I'm going to backfit my 700 with at least the different components called out on the "D".

But first... we must pause a lil.. and clean this mess up, LOL...

 

[Phase Linear Phanatic]

Sure sounds like one, David. I think Joe really hit a stride with the "D" rev's - I think I'm going to backfit my 700 with at least the different components called out on the "D".

But first... we must pause a lil.. and clean this mess up, LOL...

Why?? It's just gonna look like that again? might as well leave the equipment out!

 

[jbeckva]

Why?? It's just gonna look like that again? might as well leave the equipment out!

All the flotsam and jetsam eventually starts "organizing".... Next thing I know, there's this big pile of old components, solder, and tools that grew eyes and starts looking at me.

 

[Phase Linear Phanatic]

I still don't see a front panel shot of a 700B.

You mean like this? It's the same amp before it left?

 

[jbeckva]

Beat down the mess monster, so I'm ready to kick back and listen for awhile. Just listened to the "Kazoo Song" (Lucky Man - ELP)... couldn't have sounded better!

 

[Phase Linear Phanatic]

Beat down the mess monster, so I'm ready to kick back and listen for awhile. Just listened to the "Kazoo Song" (Lucky Man - ELP)... couldn't have sounded better!

While it is in your possession; do you notice if the meters look calibrated correctly? As in....are they both dancing the same tune if you know what I mean?

 

[jbeckva]

While it is in your possession; do you notice if the meters look calibrated correctly? As in....are they both dancing the same tune if you know what I mean?

Funny you should mention that - Yeah, I did notice one not as sensitive as the other. I"ll see what can be done, but no guarantees unless Joe or Lee know a trick or two.

 

[laatsch55]

Other than the resistors drifting in value ovr time probably not. Check the resistors to see if they are the same Jer. That's about all you can do. Just plain shiitty meters.

 

[Skratch]

Jer, If you go to Joe's website there is a way to check the meters with a battery and resistor

 

[jbeckva]

Jer, If you go to Joe's website there is a way to check the meters with a battery and resistor

That's a good tip! I'll try it, but hmm.. this one does have Joe's light board, so along with it would have been the resistors and diodes brand new. Unless that surge zapped something, but it's the left reading higher than the right (you'd think it would be the opposite?).

In any case, here's some eye candy for Lee (see told ya it was a 700B, ya "bat"... lol)

 

[Skratch]

Jer, Are the meters the same with no signal. When they are at rest they should be the same, if not you have to zero them in.

 

[jbeckva]

Jer, Are the meters the same with no signal. When they are at rest they should be the same, if not you have to zero them in.

Yep, that was what had me concerned about them.

Unless there's a physical "stop" (peg?) at zero for these types? And what I am seeing really is just one closer than the other to actual motion? (hard to describe... hehe)

 

[Skratch]

Jer There is info in the PLWO section how to zero meters in written by Joe

 

[jbeckva]

Jer There is info in the PLWO section how to zero meters in written by Joe

I know, I have done that before. These meters are "at zero", both of them.

My question is with these models, is there actually a physical "stop" at zero (look at an old vintage tape deck... a lot of them have a very small "peg" where the needle can't travel past). If there is, then I might be able to correct the issue as it could just be the needle's "motor" usable range isn't centered right.

 

[Phase Linear Phanatic]

I know, I have done that before. These meters are "at zero", both of them.

My question is with these models, is there actually a physical "stop" at zero (look at an old vintage tape deck... a lot of them have a very small "peg" where the needle can't travel past). If there is, then I might be able to correct the issue as it could just be the needle's "motor" usable range isn't centered right.

That's what I was saying way back when people kept suggesting the meter calibration. They ARE at zero. Its just when the music plays and the beat hits, one needle thumps with the thump, and the other swings wildly with the thump. It's like one side has a sport tuned suspension needle, and the other, a softer bouyant stock needle. (For analogy there). Meters ARE zero'd in, pots are in identical positions, and Joe's light board is already installed. It did that before it ever got zapped. Possible differences in pots?? Different resistances? Just stabbing in the dark here.....

 

[jbeckva]

That's what I was saying way back when people kept suggesting the meter calibration. They ARE at zero. Its just when the music plays and the beat hits, one needle thumps with the thump, and the other swings wildly with the thump. It's like one side has a sport tuned suspension needle, and the other, a softer bouyant stock needle. (For analogy there). Meters ARE zero'd in, pots are in identical positions, and Joe's light board is already installed. It did that before it ever got zapped. Possible differences in pots?? Different resistances? Just stabbing in the dark here.....

Right.. it's meter sensitivity that seems to be the deal here. I'll open 'er up and try a few ideas I have. Wish I had a "decade box", hmmmm...

 

[Gepetto]

Right.. it's meter sensitivity that seems to be the deal here. I'll open 'er up and try a few ideas I have. Wish I had a "decade box", hmmmm...

Check the 20 DB switch wiring. That is what I would first suspect

 

[jbeckva]

Check the 20 DB switch wiring. That is what I would first suspect

Even in the 0db position, there's still a difference which would lead me away from it perhaps? But yeah I did consider it... would you happen to have a pic showing the back connections? If not no prob.. I'll look into it later when I open 'er back up.

 

[Gepetto]

Even in the 0db position, there's still a difference which would lead me away from it perhaps? But yeah I did consider it... would you happen to have a pic showing the back connections? If not no prob.. I'll look into it later when I open 'er back up.

Jer
From left to right while looking at the silk screened side of the board.

Pad1 Right Channel output from amp
Pad2 Right Meter attenuation
Pad3 Ground
Pad4 Ground
Pad5 Left Meter attenuation
Pad14 LV AC in
Pad15 LV AC in
Pad16 Left Channel ouput from amp

 

[Gepetto]

Jer
From left to right while looking at the silk screened side of the board.

Pad1 Right Channel output from amp
Pad2 Right Meter attenuation
Pad3 Ground
Pad4 Ground
Pad5 Left Meter attenuation
Pad14 LV AC in
Pad15 LV AC in
Pad16 Left Channel ouput from amp

Check for blown small signal diodes especially in location D9 and D12. If the meter pegged with the negative outputs shorted in the -20dB position it could take out these diodes (doubful but worth checking)