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Ask help on PASS X150 dc output differential settings
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Old 9th October 2019, 02:33 PM   #31
Zen Mod is offline Zen Mod  Serbia
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Ask help on PASS X150 dc output differential settings
follow Wayne's instructions how to set relative and absolute offsets , but only after checking and resetting Iq of channels (halves)

see enclosed ,I'm lazy to mark them with more appropriate names , except that L means left side heatsink mounted outputs and R means same for right side heatsink mounted outputs

figure which trimpot on mainboard will invoke change for each 2pin header .... but I can bet that position of them is logical

use 2wire jack extension as shown in my blog , for measurements , to avoid shorts

set to 940mV at each readout place , in temp. equilibrium

ignore 2pin headers you marked with numbers 1,2,3,4 - they're here for shorting adjacent 100uF caps , for who knows which purpose**

**or - even better - do not ignore 1,2,3,4 , but close all four with jumpers, and short all inputs ( both negative and positive ) to GND, so you'll get what Pa described in post #23

when Iq for each output group is set where it needs to be , you still can't set all offsets where prescribed , time is for Amp Doctor
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Last edited by Zen Mod; 9th October 2019 at 02:40 PM.
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Old 9th October 2019, 03:19 PM   #32
gelly is offline gelly  Belgium
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Zen,

great !

you know i didn't notice the IQL2 and the IQR2 headers you marked ?
gee… if i just opened my eyes a bit more...

tnx for tags zen !

adjusting/measuring is not for today anymore cause of other occupations.

you wrote:

"set to 940mV at each readout place , in temp. equilibrium"
i suppose you ment 140mv (like in your blog)
"...between110mV and 140mV ;both readings must be the same"

now the IQL1 and the IQR1 are 70 and 60 mv.
if i raise that to 140 mv, the current will be more than doubled ?
meaning more dissipation, more heat...
now i measured already 50 and 48 degrees. it would be quite hotter, no ?

for the offsets, i followed yours and waynes instructions.

greetz.

Last edited by gelly; 9th October 2019 at 03:22 PM.
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Old 9th October 2019, 03:48 PM   #33
Zen Mod is offline Zen Mod  Serbia
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Ask help on PASS X150 dc output differential settings
you're right ...... 940mV is my mistake and only Papa knows from where it originates

do as Wayne said in post #15:

Quote:
There are 4 sets of pins. Two on the left and two on the right. We used a connector to a voltmeter on these. You don't want to short them be very careful. Each pot on the main board matches up with a set of pins closest to it.
Bias is set at 125mV to start check and set so they are even and temp is 45-50 C
edit: if you're chicken from any reason - choose lower Iq reading , but set them all on same number
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Last edited by Zen Mod; 9th October 2019 at 03:57 PM.
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Old 9th October 2019, 05:49 PM   #34
gelly is offline gelly  Belgium
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Quote:
Originally Posted by Zen Mod View Post
edit: if you're chicken from any reason - choose lower Iq reading , but set them all on same number
indeed some chicken in me wants to prevent eventual overheating…
double bias voltage probably would mean double the current, double the dissipated power. (now the temps are quite okay i tought…)
1st i'll measure those unmeasured pins (IQL2 and the IQR2 )
maybe they are way wrong. (and not equal)
and depending those values i would take action.

in the meanwhile,
thanx a lot for your help and patience guys !
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Old 10th October 2019, 04:03 PM   #35
gelly is offline gelly  Belgium
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back with results:

IQL1 was 60mv
IQL2 was 87mv

IQR1 was 70mv
IQr2 was 90mv

adjusted to:

IQL1 is 112,5 mv.
IQL2 is 113,7 mv.

IQR1 is 106,6 mv.
IQR2 is 107,3 mv.

bias pots are super sensitive ! had to turn a tiny hair to change lets say 5mv !
took me a while but setteled.
measurements where a bit less, and stabilized to a little bit higher (to these written values)

the differential offset between the 2 output terminals is now R=12mv L=35mv.
absolute offset between terminals and ground:
right = 5.5 vdc. !
left = 14 vdc. !

oh yes, the temperatures:
after settling, now 2 hours further…
left 47,5 and right 46,6 degrees c.
quite nice !

popping is better.
intresting is > there is no boppin when inputs are shorted.

changing dc absolute offset changes also the IQ values, so it was back and forth adjustment.

at this moment i'm quite satisfied.
of course, could not archieve this without your help guys !
tnx !

Last edited by gelly; 10th October 2019 at 04:07 PM.
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Old 10th October 2019, 04:54 PM   #36
Zen Mod is offline Zen Mod  Serbia
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Ask help on PASS X150 dc output differential settings
5V5 for absolute offset, in temp equilibrium is way too much

14V yikes! much

even if not jeopardising speakers in any way , it eats of dynamic capability of amp - swing is decreased twice that much!

you can't get less with trimpot all the way ?
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Old 10th October 2019, 05:09 PM   #37
Nelson Pass is offline Nelson Pass  United States
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Ask help on PASS X150 dc output differential settings
From all appearances, something is broken somewhere.
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Old 10th October 2019, 05:09 PM   #38
gelly is offline gelly  Belgium
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cant get less.

it variatad only lets say about 1 volt plus/minus, so i let'it in the midway of trimmer.
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Old 10th October 2019, 05:31 PM   #39
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can you confirm voltages at C6 and C7 , ref. to GND?
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Old 10th October 2019, 06:09 PM   #40
wayne is offline wayne  United States
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Ask help on PASS X150 dc output differential settings
Quote:
Originally Posted by Zen Mod View Post
follow Wayne's instructions how to set relative and absolute offsets , but only after checking and resetting Iq of channels (halves)

see enclosed ,I'm lazy to mark them with more appropriate names , except that L means left side heatsink mounted outputs and R means same for right side heatsink mounted outputs

figure which trimpot on mainboard will invoke change for each 2pin header .... but I can bet that position of them is logical

use 2wire jack extension as shown in my blog , for measurements , to avoid shorts

set to 940mV at each readout place , in temp. equilibrium

ignore 2pin headers you marked with numbers 1,2,3,4 - they're here for shorting adjacent 100uF caps , for who knows which purpose**


If you want DC coupling of course.

**or - even better - do not ignore 1,2,3,4 , but close all four with jumpers, and short all inputs ( both negative and positive ) to GND, so you'll get what Pa described in post #23

when Iq for each output group is set where it needs to be , you still can't set all offsets where prescribed , time is for Amp Doctor

You may need new modules if you can't get the DC any better.
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