100R rebuild continues

I did as you suggested, pulled out the input plug and it sounds the same. Basically the same effect as you hear in the last video with the stylus being removed. I guess that takes the motor noise and rumble of the equation? The coupler still needs to be changed, but I will have to take a look at the amp again. It WAS working fine many months ago before I shelved it to work on the cabinet. Can the resistors be reliably tested in circuit with this amp, or will I have to isolate them all?

Like all electronics--some resistors can be checked in circuit,others not--depends on the circuit-- Ron Rich

catboxer wrote:I did as you suggested, pulled out the input plug and it sounds the same. Basically the same effect as you hear in the last video with the stylus being removed. I guess that takes the motor noise and rumble of the equation?

Yep, you are looking now for "motorboating" due to a failed filter cap in the sections before the mute circuit. A microphonic tube can cause this, but that severity is really rare. Does it vary in frequency or level with the setting of the volume control?

Rob

Thanks Rob, yes the hiss and other noise increases along with the master volume. I have changed every cap with Ron T's cap kit earlier in the year.

Changing "all caps" is not an amp ( or anything else), "re-build" ! Also possible that one or more of the "new" caps has failed, but more likely something else is bad. BTW--Who is "Ron T" ? Ron Rich

Very True. And I meant Vern Tisdale, or more accurately I think it was his son...So close