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2385 reconnect PS00 to P400 pin question

dankik said:
L005 looks like it connects to LN01 so I'm not sure what is going on.
Click to expand...
Got the unit out of protection mode.
I have noticed something that may make sense to you
If i touch the volume stem when slider is fully to the right, sound dosnt change and that channel is clear
If i touch the volume stem with slider to far left , i hear a hum like ground loop and that channel has distortion
 
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I think my issue has something to do with grounding
1. No plate on front- sound left and right , right clear, left distorted
2. Face plate installed, unit will not come out of protection
3. Re removed face plate unit goes out of protection , left and right works, right clear left distorted and reacts to touch of volume shaft
4. Re install face plate unit back in protection
I cannot see any loose wire or anything shorting ,
Removed the plate now doesnt come out of protection.
 
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Wow! :dunno:

I found these errors listed while looking on the internet.
Do any of these apply to you if you changed any components?

Service Manual Errors Notated:
  • P850 PSC - C853 1000uf 25V ***printing on pCB polarity is opposite what should be
  • PT00 Filter Amp - CT23/24 47uf 16V CT24 opposite PCB polarity
  • PQ00 Soft Start - CQ05 33uf 35V (manual says 22uf 35V)
  • P700 AMP - C709/710 .47uf 50V NOT PRESENT ON EURO
 
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dankik said:
Wow! :dunno:

I found these errors listed while looking on the internet.
Do any of these apply to you if you changed any components?

Service Manual Errors Notated:
  • P850 PSC - C853 1000uf 25V ***printing on pCB polarity is opposite what should be
  • PT00 Filter Amp - CT23/24 47uf 16V CT24 opposite PCB polarity
  • PQ00 Soft Start - CQ05 33uf 35V (manual says 22uf 35V)
  • P700 AMP - C709/710 .47uf 50V NOT PRESENT ON EURO
Click to expand...
Not any i replaced.
 
I have found something that may or not affect sound. There is a wire JT04 that goes to the PT board, it is connected but does not have continuity to the pin the trace goes to.
With LN01 not working at the moment, can i test voltage at the resistors shown in the photo from the two tabs shown at the bottom center, if so are they affected by R729 for the first amp and R730 for the second
Lastly if i am correct what voltage am i looking for.
If im off here where can i test offf set voltage to see if thats affecting my LN01
 

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sendust said:
There is a wire JT04 that goes to the PT board, it is connected but does not have continuity to the pin the trace goes to.
Click to expand...
JT04 should connect to two pins on switch ST01-4 as shown with the red arrows.
1787065677506.png

sendust said:
can i test voltage at the resistors shown in the photo from the two tabs shown at the bottom center,
Click to expand...
If you are referring to the resistor leads that have a loop on them, you can measure the voltage with respect to ground and as far as I can tell they should be close to 0v.

1787066513469.png
sendust said:
are they affected by R729 for the first amp and R730 for the second
Click to expand...
R729 and R730 are used to adjust the DC Offset to 0v at the speaker terminals.
sendust said:
Lastly if i am correct what voltage am i looking for.
Click to expand...
Are you asking what voltage you are looking for when you adjust R729/R730? If yes, read below.
If you are asking about some other voltage, please be more specific.

1787066807460.png
 
dankik said:
JT04 should connect to two pins on switch ST01-4 as shown with the red arrows.
View attachment 3820644


If you are referring to the resistor leads that have a loop on them, you can measure the voltage with respect to ground and as far as I can tell they should be close to 0v.

View attachment 3820647

R729 and R730 are used to adjust the DC Offset to 0v at the speaker terminals.

Are you asking what voltage you are looking for when you adjust R729/R730? If yes, read below.
If you are asking about some other voltage, please be more specific.

View attachment 3820660
Click to expand...
This is the second time i leave the unit for a day and protection relay does not engage. and unit plays again.
I tested the bank of resistors as per photo ,both lower tabs both amps . Meter set on mvlt ,black probe connected to chasis
Amp 1 first tab 134 mlvt Second tab 134 mlvt
Amp 2 first tab 49 mlvt Second tab 67 mlvt
 

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Those readings should be closer to 0V. Did you try to adjust R729 and the one on the other channel?
 
dankik said:
Those readings should be closer to 0V. Did you try to adjust R729 and the one on the other channel?
Click to expand...
Multimeter set to mlvt, black probe to chassis , red probe to either tab at bottom of row of resistors,
Tried R729 , no change, tried R730 no chnge tried both channels same results
Maybe i have the probes connected incorrectly also unit does not come out of protection again so testing may need to be done differently.
 
For the Fluke 115, you need to:
  • Black lead to COM, Red lead to V
  • Function dial set to mV
  • Press yellow button to select DC mV
  • The display should show "mV" and "DC"
1787092195226.png
1787092432183.png
 
dankik said:
Selector set to AUX. Volume control fully counter-clockwise?
Click to expand...
Yes volume off, selector at AUX
I tested R729 powered off plug out , meter on ohm, red on center wiper . Black on left outer pin, turn trimmer, numbers travel up, reverse travel down fairly smooth
I think trimmer is good
 
What exactly are you trying to do? Are you trying to set the DC offset?
If you are measuring DC Offset, and adjusting R729, then you need to attach your DMM to measure mV across the speaker terminals and adjust to 0v.
Is that what you did?
 
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