Hi All,
I've visited & enjoyed this site a lot over the years but this is one of my first posts. Hoping I can seek some advice on output transistor selection.
I've inherited a Crown Macro Reference amp, Esoteric version with previous repairs & problems with one channel not working. The previous repairman replaced some (not all) of the original Crown C7065-3 & C7901-9 o/p's with MJ15022/23's & replaced 2 of 4 drivers with different parts as well. In addition, new emitter resistors for the MJ15022/23's with 10% instead of factory 5% units. Upon receiving the amp, I found one of the replacement drivers was not even soldered, yet the previous tech claimed it worked fine on the bench! I soldered the driver & the amp actually came to life! However the channel module is really is a dogs breakfast with 4 different o/p's, 4 different drivers & 2 different emitter resistors. 😡
Even though it is currently working, I don't trust it & want to repair properly. The Crown manual notes the C7065-3 as (MJ15004) & C7901-9 as (MJ15003). My question, are MJ15003/4's really adequate given the amp has 140v Rail to Rail? Output stage is a grounded Bridge with 3 pairs of o/p's for each half bridge. The amp is rated at 760w@8, 1160w@4 & one source states 1500w@2 ohm per channel. Yikes! that's a lot for those MJ15003/4!
Should I stick with MJ15003/4 or go to MJ15022/23 or even MJ21194/5 as many in these forums have suggested for other members repairs & projects? My apologies for the long post as I want to provide plenty of info & really appreciate any advice. FYI, I am an electronic tech, just don't repair Power amps for a living, only for myself or friends. 🙂
I've visited & enjoyed this site a lot over the years but this is one of my first posts. Hoping I can seek some advice on output transistor selection.
I've inherited a Crown Macro Reference amp, Esoteric version with previous repairs & problems with one channel not working. The previous repairman replaced some (not all) of the original Crown C7065-3 & C7901-9 o/p's with MJ15022/23's & replaced 2 of 4 drivers with different parts as well. In addition, new emitter resistors for the MJ15022/23's with 10% instead of factory 5% units. Upon receiving the amp, I found one of the replacement drivers was not even soldered, yet the previous tech claimed it worked fine on the bench! I soldered the driver & the amp actually came to life! However the channel module is really is a dogs breakfast with 4 different o/p's, 4 different drivers & 2 different emitter resistors. 😡
Even though it is currently working, I don't trust it & want to repair properly. The Crown manual notes the C7065-3 as (MJ15004) & C7901-9 as (MJ15003). My question, are MJ15003/4's really adequate given the amp has 140v Rail to Rail? Output stage is a grounded Bridge with 3 pairs of o/p's for each half bridge. The amp is rated at 760w@8, 1160w@4 & one source states 1500w@2 ohm per channel. Yikes! that's a lot for those MJ15003/4!
Should I stick with MJ15003/4 or go to MJ15022/23 or even MJ21194/5 as many in these forums have suggested for other members repairs & projects? My apologies for the long post as I want to provide plenty of info & really appreciate any advice. FYI, I am an electronic tech, just don't repair Power amps for a living, only for myself or friends. 🙂
Crown
I've inherited a Crown Macro Reference amp, Esoteric version with previous repairs & problems with one channel not working. The previous repairman replaced some (not all) of the original Crown C7065-3 & C7901-9 o/p's with MJ15022/23's & replaced 2 of 4 drivers with different parts as well. In addition, new emitter resistors for the MJ15022/23's with 10% instead of factory 5% units. Upon receiving the amp, I found one of the replacement drivers was not even soldered, yet the previous tech claimed it worked fine on the bench! I soldered the driver & the amp actually came to life! However the channel module is really is a dogs breakfast with 4 different o/p's, 4 different drivers & 2 different emitter resistors.
Even though it is currently working, I don't trust it & want to repair properly. The Crown manual notes the C7065-3 as (MJ15004) & C7901-9 as (MJ15003). My question, are MJ15003/4's really adequate given the amp has 140v Rail to Rail? Output stage is a grounded Bridge with 3 pairs of o/p's for each half bridge. The amp is rated at 760w@8, 1160w@4 & one source states 1500w@2 ohm per channel. Yikes! that's a lot for those MJ15003/4!
Should I stick with MJ15003/4 or go to MJ15022/23 or even MJ21194/5 as many in these forums have suggested for other members repairs & projects? My apologies for the long post as I want to provide plenty of info & really appreciate any advice. FYI, I am an electronic tech, just don't repair Power amps for a living, only for myself or friends.
The SOA of the 15003/4 are quite close to the MJ15xxx and MJ211xxx transistors.
The MJ15xxx and MJ211xxx are 4MHz devices whereas the MJ15003/4 ate 2MHz.
In this crude Crown circuit I doubt there is a difference. I use all three types. They are all very expensive at about $6.50 each so cost will be the same.
There is nothing wrong with running MJ15003/4 on a 140 v rail as they are specified at 140Vceo. However Crown have 22 ohm Base-Emitter resistors which pushes the breakdown voltage close to 200 anyway (Vcbo)
Steve Mantz
Zed Audio CA
I've inherited a Crown Macro Reference amp, Esoteric version with previous repairs & problems with one channel not working. The previous repairman replaced some (not all) of the original Crown C7065-3 & C7901-9 o/p's with MJ15022/23's & replaced 2 of 4 drivers with different parts as well. In addition, new emitter resistors for the MJ15022/23's with 10% instead of factory 5% units. Upon receiving the amp, I found one of the replacement drivers was not even soldered, yet the previous tech claimed it worked fine on the bench! I soldered the driver & the amp actually came to life! However the channel module is really is a dogs breakfast with 4 different o/p's, 4 different drivers & 2 different emitter resistors.
Even though it is currently working, I don't trust it & want to repair properly. The Crown manual notes the C7065-3 as (MJ15004) & C7901-9 as (MJ15003). My question, are MJ15003/4's really adequate given the amp has 140v Rail to Rail? Output stage is a grounded Bridge with 3 pairs of o/p's for each half bridge. The amp is rated at 760w@8, 1160w@4 & one source states 1500w@2 ohm per channel. Yikes! that's a lot for those MJ15003/4!
Should I stick with MJ15003/4 or go to MJ15022/23 or even MJ21194/5 as many in these forums have suggested for other members repairs & projects? My apologies for the long post as I want to provide plenty of info & really appreciate any advice. FYI, I am an electronic tech, just don't repair Power amps for a living, only for myself or friends.
The SOA of the 15003/4 are quite close to the MJ15xxx and MJ211xxx transistors.
The MJ15xxx and MJ211xxx are 4MHz devices whereas the MJ15003/4 ate 2MHz.
In this crude Crown circuit I doubt there is a difference. I use all three types. They are all very expensive at about $6.50 each so cost will be the same.
There is nothing wrong with running MJ15003/4 on a 140 v rail as they are specified at 140Vceo. However Crown have 22 ohm Base-Emitter resistors which pushes the breakdown voltage close to 200 anyway (Vcbo)
Steve Mantz
Zed Audio CA
Wow, thee Steve Mantz! 🙂 I purchased brand new & still own 2 x Zues IV's! 😎
Thanks for the info & advice on o/p's. I generally like to use factory spec parts for repairs & not "modify" but have seen so much talk of updated modern devices, so wanted to check with those more experienced. And yes, they are expensive these days at $11 CND!😱
Ross