All things G1176 - the new "repost" thread.

[Pine]

A2D I have the same PROBLEM !!!!!!!!!!!!!   

Check the 6 leg in TL071  I have -8 V  and you  ?  (when release CCW)




This is beautiful i'm from Poland in Europe     You are slipping now  and I'm working and things about 1176
My English its not good , sorry.
sosnowski Pine

 

[gswan]

The TL071 op amp is not the cause of this problem for a2d. We have isolated the section of circuit that is causing the problems.
Pin 8 of the TL071 is a NC pin, which could be substrate. Don't worry about it for now.

 

[a2d]

yes I'll agree with that, but maybe I'm missing something

  the voltage across the resistor should remain a constant regardless of the wiper positon  is this right?

if I have -9.05 V on the low side of the release pot I should have a constant voltage output on the other end of the 5 meg pot regardless of the pots positin , is this correct
if it is it sounds like a bad pot, because the voltage changes then you turn the pot

A bad pot would show either full voltage or nothing (ie open circuit). Unless you have connected the body to GND and one of the legs is shorting to GND (against the front panel etc)

 

[a2d]

nevermind the voltage should change because of the resistor on the wiper

 

[a2d]

ok I rechecked the wiring and for short again, I could not find anything wrong in this part,
Could the problem be in the signal amp side?

 

[a2d]

ok I changed the 2, bc560's and now the meter reacts better with the release pot full CCW the needle only drops to -2.5 instead of -20 and with the release full CW the meter only goes to 0
I think I may be on to something

 

[Pine]

When changed BC 560 do you do again calibration ?

BC560 be your problem ?


I don't find my problem !!! :-(

 

[a2d]

yes I had to do the calibration again ,,,, ummmm its still not right
I'm going to change
bd139 and 140 next

 

[a2d]

Pine what transistors are you using in Q1 and Q10?

When changed BC 560 do you do again calibration ?

BC560 be your problem ?


I don't find my problem !!! :-(

 

[Pine]

I change my left channel with right channel .

Now problem is with right channel .      ALL POTS and  PCB RATIO and METER is good.  Problem is only on the BIG PCB !!!!

I have  one question  , problem isn't in output transformer ?  LUNDAHL 5402 ?

 

 

[gswan]

nevermind the voltage should change because of the resistor on the wiper

This would be true if the meter's impedance was significant compared with the source impedance. Some cheap DMM's have a lower impedance when measuring volts that, in this case, would significantly affect the readings, which sounds like what we are seeing.

 

[a2d]

its a good meter from HB, when I changed the bc560's things improved greatly,
with the release pot full CCW the meter drops to -2.5 and full CW the meter goes to 0
I'm going to change the BD 139-140 later and see if that helps

Maybe when I had the fets in the wrong way it caused some damage to other components

 

[gswan]

ok I changed the 2, bc560's and now the meter reacts better with the release pot full CCW the needle only drops to -2.5 instead of -20 and with the release full CW the meter only goes to 0
I think I may be on to something

Not sure unless there are other faults in the unit. The output amplifier is not part of the GR circuit and should have no effect on the settings of the release pot. The GR amp signal tap comes from the top of the output pot, prior to the output amp.

 

[a2d]

maybe its feeding back, I'm not too sure, but its looking better  
I can tell you that everything in the GR meter/control, is good, I've tesetd 6+ times
the only thing that is not tested is the signal line amp part

 

[a2d]

spoke too soon,,,, the dist trimmer was maxxed out, I set it to middle position and now back to the same problem

 

[a2d]

If I remove the wire from pad 19 to the attack pot , the meter still moves with the release pot,

the voltage from pad 18 Q bias doesn't change with the movement of the releae pot, -1.56 v

the voltage on the low side of the releae pot is -1.57v it doesn't cange
voltage on the high side of the release pot with the pot full CCW  is -0.85v and with the pot full CW it is -1.56
voltage on the wiper is -1.56 full CCW and -1.52 this should not change

Check the wiring between point 19 and the pots. Check the circuit board for shorts at point 19. There's a problem here by the look of it.

 

[a2d]

Hey Pine have you had any luck yet??

 

[a2d]

I removed  C27, R7 , and C3 and the problem goes away the meter will only sway .5db
could it be that the fets are not mached ???

 

[Pine]

Hey a2d .


I have a new PCB and  new all komponents this is only one way for us.

Build a new channel.     


PCB RATIO and METER and ALL POTS is OK because change my left channel with right and now don;t work right channel.

 

[Pine]

http://www.fotosik.pl/pokaz_obrazek/1b08756355f6d114.html