I showed Roger this thread and he composed the following response for you. I hope this helps. cheers, Angela
It is true that a small percentage of Motorola's 4000 series Thermal Trak transistors develop faults in their thermal sensors. This causes the bias in an amplifier to increase and that channel will run hotter than normal. Fortunately, the transistor itself works properly so the amplifier continues to operate normally with very low distortion.
Unfortunately sensor failures do not occur immediately. The fault does not appear until the amplifier has been in use for weeks or months. As a result, there is no way of that a manufacturer can identify a Thermal Trak transistor that is prone to failure during his quality control and burn-in process.
Motorola has responded to their problem by discontinuing their faulty, 4000 series Thermal Trak transistors and replacing them with a new version. We here at Sanders Sound Systems have been replacing the original faulty transistors with the new ones and so far we have had no failures in the new transistors.
However, the new transistors have only been available for a few months. Before that we had to replace early faulty 4000 series transistors with more 4000 series ones. This resulted in some customers having more than one failure. This should no longer be a problem with the new transistors.
Only a small percentage of the original 4000 series transistors failed. Most Magtech customers have had no problems with their original transistors and their amplifiers continue to operate perfectly. So Magtech customers who are not having any transistor problems need not be concerned.
The bottom line here is that Motorola has taken action to fix their Thermal Trak problem. So we should not be seeing such failures in the future. Sanders' customers can rest assured that Sanders will fix any Magtech amplifiers affected by Motorola's transistor problems at no charge under their lifetime warranty.
Great Listening,
Roger
It is true that a small percentage of Motorola's 4000 series Thermal Trak transistors develop faults in their thermal sensors. This causes the bias in an amplifier to increase and that channel will run hotter than normal. Fortunately, the transistor itself works properly so the amplifier continues to operate normally with very low distortion.
Unfortunately sensor failures do not occur immediately. The fault does not appear until the amplifier has been in use for weeks or months. As a result, there is no way of that a manufacturer can identify a Thermal Trak transistor that is prone to failure during his quality control and burn-in process.
Motorola has responded to their problem by discontinuing their faulty, 4000 series Thermal Trak transistors and replacing them with a new version. We here at Sanders Sound Systems have been replacing the original faulty transistors with the new ones and so far we have had no failures in the new transistors.
However, the new transistors have only been available for a few months. Before that we had to replace early faulty 4000 series transistors with more 4000 series ones. This resulted in some customers having more than one failure. This should no longer be a problem with the new transistors.
Only a small percentage of the original 4000 series transistors failed. Most Magtech customers have had no problems with their original transistors and their amplifiers continue to operate perfectly. So Magtech customers who are not having any transistor problems need not be concerned.
The bottom line here is that Motorola has taken action to fix their Thermal Trak problem. So we should not be seeing such failures in the future. Sanders' customers can rest assured that Sanders will fix any Magtech amplifiers affected by Motorola's transistor problems at no charge under their lifetime warranty.
Great Listening,
Roger