Bryston 2B owner here.
I successfully restored a 2B, basically re-capped it, and adjusted bias.
Now I bought another one to restore, however this one is more broken...... blown fuse on one channel,, with one dead output power transistor (2N6609) and it's complimentary is suspect as well (2N3773).
I purchased 4 new MJ15025
...and 4 new MJ15024, as replacements for both channels. Only two of each will be needed.
Question, is matching the power transistors very important ? or can I rely on the matching of the (original Bryston) pre-stage low power transistors, for acceptable DC offsets ?
I successfully restored a 2B, basically re-capped it, and adjusted bias.
Now I bought another one to restore, however this one is more broken...... blown fuse on one channel,, with one dead output power transistor (2N6609) and it's complimentary is suspect as well (2N3773).
I purchased 4 new MJ15025
...and 4 new MJ15024, as replacements for both channels. Only two of each will be needed.
Question, is matching the power transistors very important ? or can I rely on the matching of the (original Bryston) pre-stage low power transistors, for acceptable DC offsets ?
"blown fuse on one channel, with one dead output power transistor (2N6609) and it's complimentary is suspect as well (2N3773)."
This symptom looks identical to what I experienced restoring my Bryston 2B, in my case I suspect it was the two power supply capacitors that had deteriorated over the years resulting in an unbalance in the DC power supply rails which caused the output power transistors to fail, along with the blown fuse.
Fortunately though it was straightforward to repair, as documented in the report "Bryston 2B Power Amplifier repair - Hints and Lessons Learned".
https://www.audiocircle.com/index.php?topic=184949.0
The complementary MJ15024G / MJ15025G sets I purchased had similar manufacturing batch numbers and didn't worry too much about matching the power transistors.
In fact, I did not need to make any adjustments to the DC offset as documented in the related report "Bryston 3Be Power Amplifier - Adjusting and Minimizing DC Offset". https://www.audiocircle.com/index.php?topic=188637.0
Final notes:
* Bryston 2B. Another interesting observation with the related Bryston 2B amplifier restoration, here the DC offset voltages are non-adjustable but being measured for the first time in 44-years and documented in the report showed a respectable -4 mV for left channel and -6 mV for right channel. Presume these low offset values were obtained by careful selection and matching of the input differential transistor pairs when the unit was manufactured in 1978.
Although it's been nearly 3 years since I completed the restoration of my Bryston 2B, happy to report there are no issues and it sounds great just like it used to.
Would be pleased to hear how your restoration turns out.
Thank you,
John
This symptom looks identical to what I experienced restoring my Bryston 2B, in my case I suspect it was the two power supply capacitors that had deteriorated over the years resulting in an unbalance in the DC power supply rails which caused the output power transistors to fail, along with the blown fuse.
Fortunately though it was straightforward to repair, as documented in the report "Bryston 2B Power Amplifier repair - Hints and Lessons Learned".
https://www.audiocircle.com/index.php?topic=184949.0
The complementary MJ15024G / MJ15025G sets I purchased had similar manufacturing batch numbers and didn't worry too much about matching the power transistors.
In fact, I did not need to make any adjustments to the DC offset as documented in the related report "Bryston 3Be Power Amplifier - Adjusting and Minimizing DC Offset". https://www.audiocircle.com/index.php?topic=188637.0
Final notes:
* Bryston 2B. Another interesting observation with the related Bryston 2B amplifier restoration, here the DC offset voltages are non-adjustable but being measured for the first time in 44-years and documented in the report showed a respectable -4 mV for left channel and -6 mV for right channel. Presume these low offset values were obtained by careful selection and matching of the input differential transistor pairs when the unit was manufactured in 1978.
Although it's been nearly 3 years since I completed the restoration of my Bryston 2B, happy to report there are no issues and it sounds great just like it used to.
Would be pleased to hear how your restoration turns out.
Thank you,
John