phase linear 400

[Sunnbobb]

inputs/outputs grounded???

Thanks for the idea, I'll check that out. Long term I might WOPL this one, but the board looks nice for now. With every measurement checking out that I described, I'm willing to bet it is something simple. Too simple for me. LOL

 

[gene french]

btw...they are not directly chassis grounded...inputs have insilators for the jacks and copper plate ...i bet it something simple too...

 

[gene french]

well, i just had to know.... went back to radio room as maria calls it.....set bias pots full ccw...powered on with dbt...totally uneventful..bulb dimmed as one would expect..dcp relay clicked on...blue led pierced the darkness....christine has a pulse...will sleep better now...
tomorrow populate last two rows after checking dc offset...and voltages...maybe play a tune or two...

 

[gene french]

well, this thing is cursed...i swear...
populated the entire outputs...
checked all transistors ..
all checked out good...
no collector to chassis shorts...

dbt lites and dims as expected...
dcp board activates and the led lites up...

rail +83.6v dc
-83.6v dc
pl20 rite channel +15.2v dc
-15.2v dc
pl20 left channel +15.2v dc
- 15.2v dc
however...

bias will not set...

fully clockwise....

rite bias 32 mv
left bias 32 mv

any ideas??
would appreciate any help....

gene

 

[Gepetto]

well, this thing is cursed...i swear...
populated the entire outputs...
checked all transistors ..
all checked out good...
no collector to chassis shorts...

dbt lites and dims as expected...
dcp board activates and the led lites up...

rail +83.6v dc
-83.6v dc
pl20 rite channel +15.2v dc
-15.2v dc
pl20 left channel +15.2v dc
- 15.2v dc
however...

bias will not set...

fully clockwise....

rite bias 32 mv
left bias 32 mv

any ideas??
would appreciate any help....

gene

Did you wire in the bias transistors correctly? With both channels acting up the same way, I would go there first.

 

[gene french]

already on it...something is off there...has to be...
thank you so much!!!!
wlll let you know shortly....
i double/triple checked the pl20...
all seems good...no swithed polarities...all transistors pointing in the right directions...
all diodes as per docs...

 

[gene french]

is this the correct pinout for the 2n3403...looking at the bottom where the legs protrude...
type cz-2
i have found conflicting data...
(1 is emitter 2 is collector 3 is base)

 

[Gepetto]

 

[mlucitt]

The Pinout of the 2N3403 is different than the currently used 2N5088. This has caused much wringing of hands and loss of hair.

 

[gene french]

that pinout matches the one i found...
thank you...
i disassembled the original bias transistor wire extensions as they came with christine...
and wired it up using the color scheme in the wopl docs and this pinout configuration...
i now have bias...but, a bit too much...
left channel 411 at full ccw...
right channel 589 at full ccw...
they do go higher if turned...
but, just wont go lower...
will start ohming resistors to make sure i did them right...

 

[Gepetto]

Are you missing R39L/R?

 

[gene french]

no sir...but i may have found something .

 

[Gepetto]

The picture you posted had them missing

 

[Sunnbobb]

Ya hey gang. I have another stump the Sunnbobb issue. I'm working on an pl400 with the PL14 Board. I haven't found anything in the service manual that deals with this issue.
Using a DBT and a variac, with no out puts, the amp fires up fine. With just the DBT, and fired up hard from 110V, the bulb lights up and dims immediately as it should.
If I connect my test speakers up (output), and fire up the amp, the DBT glows very bright, and remains on. It does the same even if I only hook one speaker up on either output.
All transistors test fine. 401 predrivers, and MJ96 drivers in correct positions on the back plane.
I replaced the Filter caps with new ones from WO, as well as the WO Bridge rectifier.
All new fuses, and none are blowing.
DC offset is less than .04 on the left channel, and .01 on the right, well within spec.
Bias is running at 4.9 MV, again, not far from spec.
The filters caps and rails are running at about 79V.
I did these tests without the speakers hooked up as I did not want to run the amp with the DBT bright.
Lastly, the Q3 and Q4 are the recommended MPS A93.

Still wondering if anyone has suggestions.. grounding seems fine

 

[Gepetto]

 

[gene french]

The picture you posted had them missing

i know, you are right, but had found it before i powered up....i went back through the plastic bags looking for parts if/when i convert to full comp...
i have them documented and set aside ....there were also a few extra resistors, etc...i confiscated them too....lolol
and at that time i found those minor, irrelevant, insignificant, unimportant resistors....lolol
so i installed them before i started testing...
seemed to be two problems upon testing...
1. seems christines techs in the past did not pay attention to the colors of the bias extension cables as per the docs...
and i trusted they were right...that was on me....should take nothing you read on ebay as gospel...
i did disassemble and matched the colors to the correct leg so it coincides with the pl docs and wopl docs...
that gave me bias, however high...
2. when i reversed the pl20 board to install the two bias extensions on the back side...i did not reverse the leads...
therefore i had the emitter and collector reversed....
that too is on me...
anyway....dc offset is 0 and -1 mv
the left and right bias are 350 mv dc...
it is playing music...
i cant thank you enough joe...and fellow techs...
joe, your kits are truly outstanding, well thought out and highly organized...and i really enjoyed building them...
i have learned a lot...and i appreciate all of the experience and generosity from phoenix forums...

gotta get the meters lit and reinstalled...
and this evil b**ch has been upgraded....
it was however very interesting....
lol

again...my sincere thanks and gratitude!!!!

 

[gene french]

did you get your problem figured out mr. sunnbobb???
i would be interested to know....

 

[Sunnbobb]

nope To simplify the issue...whenever I hookup speakers, the DBT lights up.

 

[mlucitt]

nope To simplify the issue...whenever I hookup speakers, the DBT lights up.

I was having a similar problem with a PL700B. Only with the Right Channel. I removed the Zobel Network components and that solved the problem.
Are you using the DC Protection Board?

 

[Sunnbobb]

I was having a similar problem with a PL700B. Only with the Right Channel. I removed the Zobel Network components and that solved the problem.
Are you using the DC Protection Board?

I'll give that a shot. I haven't installed the Output Relay yet. I am hoping to have the unit sorted out before making changes.