airtime
Super Member
I wanted to post this for a while now. Bob did an amazing job on this jewel of an amp. And BTW it sounds every bit as good as my coveted Latino ST-70 tube amp.
If I miss a step I hope Bob jumps in and adds to it.
First old caps out and heat sinks removed
All the old heatsink compound and mica insulators removed and heatsinks cleaned up...
Newmain filter caps on the left with the old original caps on the right
Over the last several days I have finished the relay protection board and the left amp board.
Before....
After
This is a list of some of the things Bob did as well.
I replaced the drivers with new correctly matched 2SC783 and 2SA483's with new mica insulators and Dow 340 heatsink compound making sure that the small nylon spacers were in place.
I replaced the predrivers with new matched ST 2N3440 and 2N5416's.
I replaced the differential input pair with matched and heatshrink bonded MPS6519's.
Used Vishay AML138 for the axial caps and a Panasonic FC for the 100uf tantalum C527.
Tomorrow I plan on working on the right channel amp board with the same treatment.
Those oem original type Toshiba TO66 and ST 3440/5416 transistors are rare and hard to source but they are the best and look far better than shoehorning in some TO220's like others do.
pics of the flyback diodes mod that is detailed in Service Bulletin M-250-3.
I have the new OnSemi MJE21195/96 output transistors installed on their heatsinks with new mica insulators and Dow 340 heatsink compound.
Both new 24,000uf 100v main filter caps are in ,along with their Panasonic 2.2uf poly film bypass caps....
New LED lamps using Don Haywood's premium lamps.....
If I miss a step I hope Bob jumps in and adds to it.
First old caps out and heat sinks removed
All the old heatsink compound and mica insulators removed and heatsinks cleaned up...
Newmain filter caps on the left with the old original caps on the right
Over the last several days I have finished the relay protection board and the left amp board.
Before....
After
This is a list of some of the things Bob did as well.
I replaced the drivers with new correctly matched 2SC783 and 2SA483's with new mica insulators and Dow 340 heatsink compound making sure that the small nylon spacers were in place.
I replaced the predrivers with new matched ST 2N3440 and 2N5416's.
I replaced the differential input pair with matched and heatshrink bonded MPS6519's.
Used Vishay AML138 for the axial caps and a Panasonic FC for the 100uf tantalum C527.
Tomorrow I plan on working on the right channel amp board with the same treatment.
Those oem original type Toshiba TO66 and ST 3440/5416 transistors are rare and hard to source but they are the best and look far better than shoehorning in some TO220's like others do.
pics of the flyback diodes mod that is detailed in Service Bulletin M-250-3.
I have the new OnSemi MJE21195/96 output transistors installed on their heatsinks with new mica insulators and Dow 340 heatsink compound.
Both new 24,000uf 100v main filter caps are in ,along with their Panasonic 2.2uf poly film bypass caps....
New LED lamps using Don Haywood's premium lamps.....