Normaly if the output voltage is to high the out of Z1 goes negative making Q1, Q3 en Q9 conducting heavely.If Q9 doen't get the output down it's becomming very hot.Something is keeping the output high.Q4,Q5 or Q6 leaking current or C6 shorted.
But when asked for the output voltage of Z1 nobody reacts, so only guessing.
Mona
But when asked for the output voltage of Z1 nobody reacts, so only guessing.
Mona
Excuse me Charles, I missed that.
If the output of the amp is also more or less +7V (since it is supplying the voltage to pin 2 ) it is like I discribed.Try taking out C6, without it the amp still works (less power).If the output is allright then, put in a new C.If not Q5 and/or Q6.Since you tested Q4 ok it isn't that one.
Mona
If the output of the amp is also more or less +7V (since it is supplying the voltage to pin 2 ) it is like I discribed.Try taking out C6, without it the amp still works (less power).If the output is allright then, put in a new C.If not Q5 and/or Q6.Since you tested Q4 ok it isn't that one.
Mona
Hi,
In Thread 97 I asked you to check the base of Q5&Q6 and the reading were = 7.5 volts and the Z1 pin 2 = 6.9 that means Q4 is the one causing the output of Z1 to 6.9 volts because the collectors voltage output of Q5&6 were 7.5 volts . Next time check the base of Q4. I always said that we need to be able to balance the bases of Q9 and Q4 to zero volt with R24. Another thing we can do it is short the 2 &3 to Z1 and then power on the amplifier with the light bulb and read the Z1 output pin 6. It should read zero volt. Also check the voltage of Q4.
In Thread 97 I asked you to check the base of Q5&Q6 and the reading were = 7.5 volts and the Z1 pin 2 = 6.9 that means Q4 is the one causing the output of Z1 to 6.9 volts because the collectors voltage output of Q5&6 were 7.5 volts . Next time check the base of Q4. I always said that we need to be able to balance the bases of Q9 and Q4 to zero volt with R24. Another thing we can do it is short the 2 &3 to Z1 and then power on the amplifier with the light bulb and read the Z1 output pin 6. It should read zero volt. Also check the voltage of Q4.
All the class-B biased Phase Linears do this - connect the bootstrap cap to the driver's output rather than the output proper. Probably becasue they found that the class-B crossover distortion was less that way. At very low output, the speaker current catually comes off the drivers, not the outputs. Unfortunately, it's really a bad plan because leakage current is amplified.
Replace the cap with a fresh one and any problems associated with it go away. Until next time. IF your amp can safely be biased slightly into AB you can return the bootstrap where it is "supposed" to go. Not all driver/output combinations used over the years in these amps can. Some of them will oscillate like crazy if you do.
Replace the cap with a fresh one and any problems associated with it go away. Until next time. IF your amp can safely be biased slightly into AB you can return the bootstrap where it is "supposed" to go. Not all driver/output combinations used over the years in these amps can. Some of them will oscillate like crazy if you do.
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