Hello Everyone,
I am relatively new to the forum and have electronics basic knowledge only. I enjoy this as a hobby and love older analog amplifiers.
I am trying to resurrect an old MX-1000 that has seen significant abuse in its time. I have some spare parts from a donor amp and need to get additional components to complete the job. So far I was able to replace all bad components on the main board with original parts from the donor, and I am trying to test it before I move on to the Sub Circuit 1 and 2 / amp boards.
The problem I am having at the moment with the main board, is that the LB rail is to high. It is 50-51v and it is suppose to be around 42v. The high voltage rail is right on the money at 91-92v.
Two transistors, both 2SC3416 and four 10K 2watt resistors are getting pretty hot.
Both transformers check OK, with roughly 68.9v 30.2v 0 30.2v 68.9v
I am trying to individually repair all boards in the amplifier. The test was done with the main board connected to power only. No sub circuit boards connected to it.
Additionally, I have connected the donor board with a different set of capacitors to power and got the same result on the LB rail (except no hot transistors which the donor board no longer has).
What could be the reason for the higher voltage on the LB rail?. Am I testing this wrong without the amp boards connected? The voltage across the 40,000uf capacitors which are rated ar 50v is 50-51v so the risk of losing the main capacitors is there.....
Please help!
I am relatively new to the forum and have electronics basic knowledge only. I enjoy this as a hobby and love older analog amplifiers.
I am trying to resurrect an old MX-1000 that has seen significant abuse in its time. I have some spare parts from a donor amp and need to get additional components to complete the job. So far I was able to replace all bad components on the main board with original parts from the donor, and I am trying to test it before I move on to the Sub Circuit 1 and 2 / amp boards.
The problem I am having at the moment with the main board, is that the LB rail is to high. It is 50-51v and it is suppose to be around 42v. The high voltage rail is right on the money at 91-92v.
Two transistors, both 2SC3416 and four 10K 2watt resistors are getting pretty hot.
Both transformers check OK, with roughly 68.9v 30.2v 0 30.2v 68.9v
I am trying to individually repair all boards in the amplifier. The test was done with the main board connected to power only. No sub circuit boards connected to it.
Additionally, I have connected the donor board with a different set of capacitors to power and got the same result on the LB rail (except no hot transistors which the donor board no longer has).
What could be the reason for the higher voltage on the LB rail?. Am I testing this wrong without the amp boards connected? The voltage across the 40,000uf capacitors which are rated ar 50v is 50-51v so the risk of losing the main capacitors is there.....
Please help!
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