Hey everyone,
I have this Recoton NHT SUB TWO amplifier with tracking down coverters. It's build the same way as Bob Carvers Sunfires subs. I know they are famous for being hard to repair. This is a tricky one but I feel I am so close to get it purring again and I just cant give up 🙂. Anyone here that has experience with these power tracking circuits?
The negative side is working and I can set idle voltage to -6,5v (between JP2 and SPK+) with RP2. as is recommended, the voltage follows the input signal.
On the positive side I have just 0,630v at idle (between JP1 and SPK+) I have no room to adjust with RP1 if I would go over 0,8v it would fry the MOSFETS.
It should be adjustable to +6,5v
However, The opto couplers seem to work fine. The zeners are feeding them 5.1v and their output is varying with the audio input signal amplitude. Even the MOSFETs are reacting with the input audio signal but not with the same swing.
The positive side goes from 6,86v at idle to 10,52v at 300mvRMS 80hz input. (meassured at S on Q22-Q24)
The negative (working) side goes from -1,86v at idle to -14,6v at 300mvRMS 80hz input. (meassured at D on Q19-Q21) all relative to AGND.
All electrolytes has been replaced and all passive components have been meassured.
The +down converter voltage being 0,6v at JP1 is an obvious problem.
Is the problem for sure in the positive tracker or could it be in the Drive amp section?
Any thoughts on were to focus next or any general remarks would be highly appriciated. I know this is an old amp but it would be so neat If I could get it up and running. 🙂
I have found this thread that helped me alot from 2008
I have this Recoton NHT SUB TWO amplifier with tracking down coverters. It's build the same way as Bob Carvers Sunfires subs. I know they are famous for being hard to repair. This is a tricky one but I feel I am so close to get it purring again and I just cant give up 🙂. Anyone here that has experience with these power tracking circuits?
The negative side is working and I can set idle voltage to -6,5v (between JP2 and SPK+) with RP2. as is recommended, the voltage follows the input signal.
On the positive side I have just 0,630v at idle (between JP1 and SPK+) I have no room to adjust with RP1 if I would go over 0,8v it would fry the MOSFETS.
It should be adjustable to +6,5v
However, The opto couplers seem to work fine. The zeners are feeding them 5.1v and their output is varying with the audio input signal amplitude. Even the MOSFETs are reacting with the input audio signal but not with the same swing.
The positive side goes from 6,86v at idle to 10,52v at 300mvRMS 80hz input. (meassured at S on Q22-Q24)
The negative (working) side goes from -1,86v at idle to -14,6v at 300mvRMS 80hz input. (meassured at D on Q19-Q21) all relative to AGND.
All electrolytes has been replaced and all passive components have been meassured.
The +down converter voltage being 0,6v at JP1 is an obvious problem.
Is the problem for sure in the positive tracker or could it be in the Drive amp section?
Any thoughts on were to focus next or any general remarks would be highly appriciated. I know this is an old amp but it would be so neat If I could get it up and running. 🙂
I have found this thread that helped me alot from 2008