Greetings,
I have an API 554 on my bench that is behaving oddly. The mid band works properly, but the high and low seem to stay engaged whether the EQ in/out switch is engaged or not. Also, they only seem to cut - even when turned to the boost positions.
I think the switching FETs are to blame, but the part number (TIS-75) has been obsoleted. The only equivalent shown on alltransistors.com is also obsolete. I sent an email to API, but no reply. Can anyone recommend a suitable replacement?
Schematics for the EQ are in the Tech Docs section here:
https://groupdiy.com/index.php?topic=44738.msg561000#msg561000
Thanks,
Mike
I have an API 554 on my bench that is behaving oddly. The mid band works properly, but the high and low seem to stay engaged whether the EQ in/out switch is engaged or not. Also, they only seem to cut - even when turned to the boost positions.
I think the switching FETs are to blame, but the part number (TIS-75) has been obsoleted. The only equivalent shown on alltransistors.com is also obsolete. I sent an email to API, but no reply. Can anyone recommend a suitable replacement?
Schematics for the EQ are in the Tech Docs section here:
https://groupdiy.com/index.php?topic=44738.msg561000#msg561000
Thanks,
Mike