phase linear 400

gene french said:
yes sir, they do go to the q3s on the back wall....is that what you wanted me to measure????
and no sir, i have not changed those....
Click to expand...
sorry....that was joe that wanted that voltage measured....
but, q5 and q8 are correct....and those i changed are on the left channel....the one working properly for the moment....
q8 right checks ok....
q5 right shows shorted in every possible combination....
here we go again....
this is what happened on the left channel a while back...
CRAP...
 
gene french said:
sorry....that was joe that wanted that voltage measured....
but, q5 and q8 are correct....and those i changed are on the left channel....the one working properly for the moment....
q8 right checks ok....
q5 right shows shorted in every possible combination....
here we go again....
this is what happened on the left channel a while back...
CRAP...
Click to expand...
I think you can lift D6 and D7 (unsolder one side of the diode and lift it out of the way) and that removes the protection circuit.
do you have another Q5?
 
yes sir...i do....george of the jungle sent me one he had....he got it from someone who claimed to use it as a guitar amp....
and only used one channel....and told george it was all working when he scavenged the board....
this is my source of q5s....used one from this 14b board....
both q5s tested differently....one passed more forward voltage than the other....they dont test open or shorted....
but the one i used on the left side was closer to my reading for the then good q5 in my 400c board....
when joe sent my kit...i bought a few extras...but are not here yet...
looking up the data sheet now...so i can be positive of how i am doing it...
 
gene french said:
sorry....i guess i did not understand...my apologies

e to c on left channel plus or minus 2.3v depending on polarity of leads to dvm
e to c on right channel plus or minus 1.3v depending on polarity of leads to dvm

View attachment 66030
Click to expand...
So you have zeroed in on where your problem is now....You are down to Q3, the bias transistor and diode D5. I know where my money is
 
Gepetto said:
So you have zeroed in on where your problem is now....You are down to Q3, the bias transistor and diode D5. I know where my money is
Click to expand...
q5 on right channel is shorted....all configurations....no doubt...
d5 i have checked twice...in circuit...
q3 checks good......
you are thinking the bias transistor????
 
Gepetto said:
So you have zeroed in on where your problem is now....You are down to Q3, the bias transistor and diode D5. I know where my money is
Click to expand...
I would take that bet,
Sorry Gene , he has more than one problem, Should Gene take out D6 and D7? (or lift the legs )
since he blow that part up the circuit out , might have other shorted parts

The good news I have my WOB control board done and putting in the amp now
 
MusicSteve said:
I would take that bet,
Sorry Gene , he has more than one problem, Should Gene take out D6 and D7? (or lift the legs )
since he blow that part up the circuit out , might have other shorted parts

The good news I have my WOB control board done and putting in the amp now
Click to expand...
good news for a change....sure would like to see pics music man!!!
 
gene french said:
q5 on right channel is shorted....all configurations....no doubt...
d5 i have checked twice...in circuit...
q3 checks good......
you are thinking the bias transistor????
Click to expand...
Well now that you told us the protection transistor is shorted, get it out of there and you should be all good. Q5 is not used in normal operation
 
Gepetto said:
Well now that you told us the protection transistor is shorted, get it out of there and you should be all good. Q5 is not used in normal operation
Click to expand...
i just checked q5 again when music man suggested checking around r14...last i checked it was good...i already changed left side...
i think i have more than one issue...
i got my schematics and gonna go component by component before i power up...
 
gene french said:
i just checked q5 again when music man suggested checking around r14...last i checked it was good...i already changed left side...
i think i have more than one issue...
i got my schematics and gonna go component by component before i power up...
Click to expand...
Gene
your going in the right direction and you started at the ground and everything can build up from their , I still like to see the protection circuit by passed for now.
what you think Joe?
 
MusicSteve said:
Gene
your going in the right direction and you started at the ground and everything can build up from their , I still like to see the protection circuit by passed for now.
what you think Joe?
Click to expand...
Sure, either that or bug out all the fried components...
 
ok....i checked everything on the board....all resistors compared side per side and by values....all transistors as i have put the q5 i had back in circuit...
all diodes....removed shorted d6...and the polarity of all the caps again...i did not check the non polarized caps that i just installed in the recap kit...
i have compared the traces against the trace map in the service manual...i have touched every solder joint on the board....
i will inspect again....
i am trying to find the value of d6....i have a few diodes and this 14b board....
i did find 2 problems on the board.....thankfully i cleaned them before i powered up again....
i really have to pay attention....
1653604156420.png

everything else looks ok....i will return tomorrow....as i am very tired and prone to more mistakes than i normally make...
too tired to lol...

i appreciate very very much....i want to get all of the fubar out of my system before joes masterpiece gets here...
i need this experience....and dont regret one of my mistakes....hopefully i will improve ....if i dont improve it will not be due
to my lack of trying...
 
gene french said:
ok....i checked everything on the board....all resistors compared side per side and by values....all transistors as i have put the q5 i had back in circuit...
all diodes....removed shorted d6...and the polarity of all the caps again...i did not check the non polarized caps that i just installed in the recap kit...
i have compared the traces against the trace map in the service manual...i have touched every solder joint on the board....
i will inspect again....
i am trying to find the value of d6....i have a few diodes and this 14b board....
i did find 2 problems on the board.....thankfully i cleaned them before i powered up again....
i really have to pay attention....
View attachment 66031

everything else looks ok....i will return tomorrow....as i am very tired and prone to more mistakes than i normally make...
too tired to lol...

i appreciate very very much....i want to get all of the fubar out of my system before joes masterpiece gets here...
i need this experience....and dont regret one of my mistakes....hopefully i will improve ....if i dont improve it will not be due
to my lack of trying...
Click to expand...
Good, you wore us out :-)
 
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