Hi all
I'm trying to repair an almost 40 year old Technics SU-V3 amplifier. It's a classic circuit design - almost completely made up of discrete components, with very few IC's. The fault is manifesting itself as the speaker protection relay not activating. This appears to be because there is a large negative DC voltage on the power amp stage, and the protection circuit is supposed to protect from DC on the speaker outputs (amongst other things).
I have a copy of the service manual which includes voltage measurements to take at various points in the circuit. However my own analog electronics is a bit rusty and I could do with some help. I've taken some measurements which certainly show some issues, but I'm not clear what parts I need to replace to resolve the issue.
Happy to post more details including marked up schematics - can anyone give me a hand with this?
Many thanks
James
I'm trying to repair an almost 40 year old Technics SU-V3 amplifier. It's a classic circuit design - almost completely made up of discrete components, with very few IC's. The fault is manifesting itself as the speaker protection relay not activating. This appears to be because there is a large negative DC voltage on the power amp stage, and the protection circuit is supposed to protect from DC on the speaker outputs (amongst other things).
I have a copy of the service manual which includes voltage measurements to take at various points in the circuit. However my own analog electronics is a bit rusty and I could do with some help. I've taken some measurements which certainly show some issues, but I'm not clear what parts I need to replace to resolve the issue.
Happy to post more details including marked up schematics - can anyone give me a hand with this?
Many thanks
James