I guess that's how it was working, luckily it never got a too high voltage from a non regulated PSU.1024MAK wrote: ↑Fri Mar 10, 2023 1:32 pm I can’t remember how power hungry the TEA2000 is. But it’s not going to be too much for a boost converter run off the +5V rail.
The alternative arrangement would be to link the +9V and +12V rails again (and remove any of the existing components that would not like this) and use a 12V regulated PSU. The downside being (1) the 7805 and heatsink would get hotter and (2) it will only work correctly with a 12V regulated PSU.
I case I decided to keep struggling for the original design what would be thebnext step? I,ve changed all electrolytics involved but the 4.7uF one (5v are really smooth at tr5 emiter) both transistor changed with the replacements I can get here..
Change diodes? Can I use common rectifier ones like 4007? or should I use signal ones like 1n4148?
What can I check at tr4 and Tr5?
And how do I check the coil? I can't replace it easily unless for a (really) dead 48k board I can use as a Donor...