reversed C25

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reversed C25

Postby RobSac » Tue Jun 21, 2016 4:32 pm

when I power it up I am getting 15v to R40 and it gets hot immediately. Not sure how much damage reversing the polarity of c25 has done if any one can share some insight it would be greatly appreciated

Im getting low voltage to q6 and turning r39 has no affect.

c26 is only seeing 20v also.

Thought I had everything triple checked but I guess I missed one.
RobSac
 
Posts: 3
Joined: Tue Jun 21, 2016 3:08 pm

Re: reversed C25

Postby RobSac » Thu Jun 23, 2016 5:16 pm

Transistor voltage measurements are

Q1 C-3.6 B-2.2 E-1.6
Q2 C-11.3 B-3.6 E-3.0
Q3 C-19.2 B-11.3 E-10.7
Q4 C-12.2 B-6.9 E-6.3
Q5 C-16.4 B-12.2 E-14.4
Q6 C-16.4 B-14.4 E-13.7(with r39 turned fully CC)
RobSac
 
Posts: 3
Joined: Tue Jun 21, 2016 3:08 pm

Re: reversed C25

Postby RobSac » Thu Jun 23, 2016 8:03 pm

ok after looking at the voltages it appeared Q5 was the problem. I tested on the board and it giving voltage between the collector and emitter, I found a NTE equivalent locally until I can get the proper replacement from Mouser.

All the voltages fell into place and I was able to adjust r39 for 22.2v.
Tested with a microphone and it seems to be working well!

Frustrating lesson for sure, I was sure everything was placed correctly. I've done many diy projects before and must have been a little over confident!

Cheers
RobSac
 
Posts: 3
Joined: Tue Jun 21, 2016 3:08 pm


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