phase linear 400

[George S.]

what is the minimum i can power on with....just the bottom two rows on left side???

On the WOPLs, we start with bottom row, check bias, then next row, check bias, next row, etc. On a original quasi backplane, I don't know. I don't see how it would be any different. I may be wrong.

 

[George S.]

Gene, the guy I bought the amp that board came out of said he used it as a guitar amp and the amp worked fine. But, I never even plugged it in before stripping it.

 

[VSAT88]

Since this thread shows 1499 reply's here is another one to make it 1500.

 

[VSAT88]

Damn, it was at 1502 already..

 

[gene french]

Damn, it was at 1502 already..

youre a day late....and a dollar short....lol

 

[gene french]

Gene, the guy I bought the amp that board came out of said he used it as a guitar amp and the amp worked fine. But, I never even plugged it in before stripping it.

understood....i just trust these old boards....they have gremlins...

 

[gene french]

i can always swap sides with q5 and q8...to see if it follows the transistors....
something is breaking down....or it would come up bad and not wait 30 seconds or so...

 

[George S.]

There is a way to bypass the bias transistors with a diode to simplify troubleshooting, but you'll have to search the forum on how to do it. Never done it myself, but it's been mentioned many times.
Long day today and again tomorrow. Later. Don't smoke more parts, sometimes it's good to step back away from it, think and sleep on it, tomorrows another day. Perhaps there's good info in the WOAD Tech Docs that'll help.

 

[Gepetto]

what is the minimum i can power on with....just the bottom two rows on left side???

Bottom row only is sufficient

 

[Gepetto]

There is a way to bypass the bias transistors with a diode to simplify troubleshooting, but you'll have to search the forum on how to do it. Never done it myself, but it's been mentioned many times.
Long day today and again tomorrow. Later. Don't smoke more parts, sometimes it's good to step back away from it, think and sleep on it, tomorrows another day. Perhaps there's good info in the WOAD Tech Docs that'll help.

You put a jumper between C-E of the bias transistor, it takes the bias to zero.

 

[Gepetto]

Gene, the guy I bought the amp that board came out of said he used it as a guitar amp and the amp worked fine. But, I never even plugged it in before stripping it.

And he only used the left channel

 

[gene french]

There is a way to bypass the bias transistors with a diode to simplify troubleshooting, but you'll have to search the forum on how to do it. Never done it myself, but it's been mentioned many times.
Long day today and again tomorrow. Later. Don't smoke more parts, sometimes it's good to step back away from it, think and sleep on it, tomorrows another day. Perhaps there's good info in the WOAD Tech Docs that'll help.

already watchin the tube..lol...youre a good guy...
thank you...

 

[gene french]

Bottom row only is sufficient

thank you...

 

[George S.]

Gene, your dealing with a bunch of unknowns with all those old parts, so try this. Remove the top 3 rows of outputs leaving only one bottom output in each column. Test for stabile bias and DC on the speaker jacks. If unsuccessful, add no more outputs until you find the issue. If successful add another row, and retest.
This is part of "the bringing up procedure" in the docs. I didn't do this in my latest S1 upgrade thread because I had a working amp prior to the upgrades which didn't involve the outputs
Best practice is bring it up row by row and check for issues with each row.
I'm thinking your going to find a leaky output or shorting socket like Andrew had on his 700 S1. He said the DC would rise as he tightened a screw, a bad socket.
Read the tech docs about populating the outputs and bringing up a WOPL.

 

[gene french]

Gene, your dealing with a bunch of unknowns with all those old parts, so try this. Remove the top 3 rows of outputs leaving only one bottom output in each column. Test for stabile bias and DC on the speaker jacks. If unsuccessful, add no more outputs until you find the issue. If successful add another row, and retest.
This is part of "the bringing up procedure" in the docs. I didn't do this in my latest S1 upgrade thread because I had a working amp prior to the upgrades which didn't involve the outputs
Best practice is bring it up row by row and check for issues with each row.
I'm thinking your going to find a leaky output or shorting socket like Andrew had on his 700 S1. He said the DC would rise as he tightened a screw, a bad socket.
Read the tech docs about populating the outputs and bringing up a WOPL.

yes sir....will do...
joe said one row will surfise to start...which is the row of driver transistors

 

[Gepetto]

yes sir....will do...
joe said one row will surfise to start...which is the row of driver transistors

You cannot drive much with this configuration but you can certainly do all your debug with just the bottom row in.

 

[gene french]

only bottom row...
top meter right
big meter left

 

[gene french]

set both offsets to zero...
set both bias to 350...
left channel bias pot no longer at the stop...
has two way adjustment from the present position...
will proceed to add one row of 909s
this test was done with only the bottom row of driver transistors...
as per joe and george...

 

[gene french]

second row in....
no dc on outputs....
left offset and right offset set to 0...was off a bit...but well within tolerances
right bias set to 350mv
left bias set to 320mv when pot runs out of adjustment....
i think i will change left and right 909s...to see if it follows the transistors ...

 

[George S.]

second row in....
no dc on outputs....
left offset and right offset set to 0...was off a bit...but well within tolerances
right bias set to 350mv
left bias set to 320mv when pot runs out of adjustment....
i think i will change left and right 909s...to see if it follows the transistors ...

Try swapping in a different set of outputs first in that second row.