BIG problems

laatsch55

laatsch55

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I'm still sending you a care package.....Can't believe someone is still sending out the 5401's and 5172's. It's not that they're bad parts, just that there is much better out there for the same price.
 
Michael F

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laatsch55 said:
Good enough for a reference, yes. Q4 should not have been used for Q4. Q4 is the hardest working TO-92 in there. The e-bay seller should know that. It'll do to get you up and running, but it's not something that inspires a medal for reliability. Are you sure about Q6's number??
Click to expand...
On my parts list, Q6 2N3415,16,17
If memory serves, I installed the 15
 
Gepetto

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Michael F said:
Q1 MPS5172
Q2 Same
Q3 2N5401
Q4 Same
Q5 2N3439
Q6 2N3415
Q7 2N5415
Q8 2N1304
Q9 2N1305
Q10 2N3440
Click to expand...
Q4 should not be a 2N5401, Vcb is too low for a PL700 application. Should be MPSA92 or 93.

Q10 should also be a 2N3439

Where did this parts list come from?
 
Michael F

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Gepetto said:
Q4 should not be a 2N5401, Vcb is too low for a PL700 application. Should be MPSA92 or 93.

Q10 should also be a 2N3439

Where did this parts list come from?
Click to expand...
All semi`s came from the same EBay source.
All semi`s are mirrored channel to channel. If the Left channel is "good" it has the identical parts in the Right channel
 
Gepetto

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Michael F said:
All semi`s came from the same EBay source.
All semi`s are mirrored channel to channel. If the Left channel is "good" it has the identical parts in the Right channel
Click to expand...
Have you started ohming out the resistors in the bad channel looking for a blown resistor?
 
Michael F

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laatsch55 said:
Have you double checked the pinouts? Solder bridges? Did you replace any of the diodes? And double check the back to back you put on C6 to make sure they're going opposite of each other.
Click to expand...
All transistors are in the proper positions. After installing a component, it was tested for shorts on the trace.
Back to back C6 diodes OK.
The only diode that was replaced was the shorted D9
 
Michael F

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Tested resistors, all good. I did find a "future" problem in R39 which had come off the base buss bar. That unfortunately did not solve the current issue.
Standing by for further instructions.
 
laatsch55

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Michael, I know this may seem tedious, I have done all the things I'm questioning about right now. I have probably screwed up a PL amp as bad as anybody ever has....BUT I was helped through it. Do not think we do not believe you when it seems we are asking the same question again. It means we want to know the answer to the same question AFTER you've done something. Long distance help in a deal like this is not ideal, but it is doable.

Did the e-bay seller provide you with data sheets showing pinouts??
 
laatsch55

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Michael, when you check for shorts in semiconductors, what you are determinming is that it's not shorted or open., Whether it has gain or not is another question. A transistor needs gain to accomplish anything, otherwise it can appear benign, and that's not helping either.
 
Michael F

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laatsch55 said:
Michael, I know this may seem tedious, I have done all the things I'm questioning about right now. I have probably screwed up a PL amp as bad as anybody ever has....BUT I was helped through it. Do not think we do not believe you when it seems we are asking the same question again. It means we want to know the answer to the same question AFTER you've done something. Long distance help in a deal like this is not ideal, but it is doable.

Did the e-bay seller provide you with data sheets showing pinouts??
Click to expand...
I have absolutely no problem carrying out any and all of your requests, whatever it takes.

Yes, I did receive data sheets with the transistors, see attachment
 

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laatsch55

laatsch55

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Unsolder and lift one leg of D9. Power back up and see if you still have 40v+dc . Also check rail votage. I want to see just how high it goes with the DBT you have in line...
 
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