There is also a bypassed emitter resistor on Q2 and R from base to ground. Then the other cap coupled stage, but that can’t blow up if something’s wrong with it. Can be ignored for the time being.
And if the big cap is shorted, is an external one (probably bigger for more bass) being used in series with the speaker?
And if the big cap is shorted, is an external one (probably bigger for more bass) being used in series with the speaker?
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so thing i drawn was this ? are you sure it is 100% right ? if is can you guys tell the issue
mostly that schematic is not really important to me because i am not expert, but i hope all i provided is enough for you guys to finally tell me what is wrong. also if you have any question about amp i will always reply 😀
There are only so many ways of doing this. By doing this, you can at least identify everything, so if something is amiss you’ve got some idea what it should be. R6 and 7 should be about half an ohm. R4 and 5 should be the same, and a couple hundred ohms (look like 220 being used). R1 and 2 should be a couple of k ohms. Bias stack two diodes and a 47 ohm resistor. Get these right, with good transistors, and it should come up without any fireworks. Then adjust the pot to center the voltage on the + side of the output cap.
An open bias stack is the most common reason things will just explode after replacing all the burnt transistors/resistors. CHECK it, out of circuit. It’s the only way to be sure. If the parts look crusty in any way replace it with two fresh 1N4002 diodes and a brand new 47 ohm metal oxide or wire wound (near burn out proof) resistor. DO NOT use carbon film or carbon comp. You want something that has zero chance of failing open, ever again.
Those diodes are really supposed to be mounted to the output transistor heat sink to prevent bias drift and thermal run away. Mounting those diodes to the sink is a major problem, though, which is probably why that step was skipped. With normal use and large enough emitter resistors (why 0.47 or larger was suggested), it should be fine. If the heat sink heats up and keeps heating up just sitting there it would need to be addressed. Cross that bridge if you ever get to it. It may just stay cool and never be an issue if you’re not running the amp hard.
An open bias stack is the most common reason things will just explode after replacing all the burnt transistors/resistors. CHECK it, out of circuit. It’s the only way to be sure. If the parts look crusty in any way replace it with two fresh 1N4002 diodes and a brand new 47 ohm metal oxide or wire wound (near burn out proof) resistor. DO NOT use carbon film or carbon comp. You want something that has zero chance of failing open, ever again.
Those diodes are really supposed to be mounted to the output transistor heat sink to prevent bias drift and thermal run away. Mounting those diodes to the sink is a major problem, though, which is probably why that step was skipped. With normal use and large enough emitter resistors (why 0.47 or larger was suggested), it should be fine. If the heat sink heats up and keeps heating up just sitting there it would need to be addressed. Cross that bridge if you ever get to it. It may just stay cool and never be an issue if you’re not running the amp hard.
so i should replace both 2n3055 and resistors for them 0.47ohm ? and it should work btw i already replaced diodes and that arrangement works
While people are deciding wich is the correct schematic, could you make a small audio clip so we can hear that choking sound?
I agree with wg_ski. That trimpot + diodes and resistor should be replaced to prevent future failing.
Are you absolutely sure that the big transistors have no shorts between pins and case?
Please check that again.
Please check that again.
When the speaker is shorted, if the 2N3055 has not broken through,
the small upper transistor may burn out first.
the small upper transistor may burn out first.
Yes, but the amp seems to play on it's drivers so there's something with the output transistors.