So, here I go. Phase Linear 400

[VSAT88]

Nite James, good job...

Thank you Sir !

 

[VSAT88]

Just checked bias again .349 Left .357 is the lowest I can adj. the Right.
DC offset is 13.6 on the Left. - 007. on the Right Don't really understand the - reading. Polarity on the meter is correct. Don't think it makes a difference but you are the authority on these amps..

 

[Billboard]

negative readings on offset do not matter, just need to be as close to zero as possible, positive or negative.

 

[VSAT88]

negative readings on offset do not matter, just need to be as close to zero as possible, positive or negative.

Hey thanks, I didn't think so but I found that I did not know so much about these amps and figured I better ask.

 

[laatsch55]

For a stocker those are excellent numbers on the offset. Bias can be affected by quite a few things, nasty ol adjustment pot, out of spec resistors, etc...those are still good bias numbers...

 

[VSAT88]

Down below I wrote about getting all new OPT. Do I need to do that ? I would just as soon not if I do not need to. And now some more news. A careful check of the shop revealed that I did not throw away the Mica insulators. I found plenty to finish this amp, brand new. I did as you said. DBT/Veriac check bias / dc offset. After warming up about 10 min or so I have.
Bias Left .353 Right .357 that is with both pots turned all the way to minimum.
DC Offset Left 12.5 mV. Right 1.0
This is with all 909 transistors in. 120V AC pulling 0.05 A at idle. Update. AC/DC sounds great so I moved on to a real test. Bolt Thrower, Hard to stay in the shop for any period of time..Had to turn it down or go deaf. Then Oh yes..Mastodon sounds great too. Amp stays cool even running it at 80 watts or so for long periods.

 

[WOPL Sniffer]

Chances are, with no more adjustment available, the amp (and your speakers) may be doomed to an untimely death.

Tick tick tick.....

 

[WOPL Sniffer]

If you cant adjust it, i hope the amp can. Get out the fan and make sure its going up and down. I ALWAYS check mine, course, mine will adjust with a tweeker too.

 

[VSAT88]

If you cant adjust it, i hope the amp can. Get out the fan and make sure its going up and down. I ALWAYS check mine, course, mine will adjust with a tweeker too.

Good lawd, that don't sound so good. Yes, both bias pots are all the way to the minimum setting. I hate to say this but I do not understand anything you said about the fan, or the tweaker..

 

[laatsch55]

What is the upper limit on the bias pots??

 

[VSAT88]

What is the upper limit on the bias pots??

I can go to the shop and find out but best I recall it was around .370 I really never tried to make it go higher because I was looking for the .350 mark

 

[laatsch55]

Na, no biggie, just curious...

 

[WOPL Sniffer]

So it will adjust.....

 

[VSAT88]

Already done. .620 left and .617 on the right.

 

[laatsch55]

Hookay, Thanks James..

 

[VSAT88]

Hookay, Thanks James..

You guys are scarring me.

 

[laatsch55]

You've got DC protect, you're good...

 

[VSAT88]

I thought it would not matter so much about the OPT as I had that DC protect in place but that was why I was asking in an earlier post today do I need to order and change out all the OPT. Should I just run these and don't worry about it or get all new ?

 

[laatsch55]

Well. it's a case of "where do you stop". Everything needs replaced in that amp as far as us White Oak nuts think. But if you aren't going to run it hard, I'd run it as is. Until it won't run anymore or if you're ready to take it up a few notches....

 

[VSAT88]

Well now, I am beginning to understand. To WOPL and beyond. I am looking for that PL 700 Now. Thanks a million all ya'll once again. If I can be of help to anyone shoot me a line. No shit, I got a lot of stuff and if you guys need anything I would be more than glad to help. I will keep my eye on the threads here to see whats up.