Hello all, want to start by saying thanks for all the help up to this point. I have learned so much and yet still tons to learn and a tape machine to fix.
I havent given up but had to leave town for work and i was also waiting for a new filter pcb to arrive from tascam ninja as mine was properly butchered….
I spent the whole day today messing around with the machine and here are my findings.
Current problem: with the power supply and amplifier connected, i have .3vac at every RCA output.
The output rails for all the voltages on the PS are clean, EXCEPT the +15/-15 audio rails. I read about 0.8vac on them when the amplifier is disconnected and when i connect the amp it drops to around 0.3vac on both rails. There is another filter PCB in the amp unit, and it seems like its doing its job, judging by the scope and ACmVM, we drop down to about 0.15vac, it appears the PS output is just too dirty for it to overcome. I thinks.
(Nothing else connected to the PS or AMP box.)
I understand the Power supply is the culprit. I need help diagnosing the linear voltage regulator (which i already replaced) and the transistors in its circuit. When i scope on the voltage regulator board in the PS i see no change in noise on my scope from the input to the board to its output to the audio rail connector.
What i tired: i wired two 1000uf caps at the final output (sens board) between the 15/0/-15 rails which resulted in the noise coming down to about .1vac ( according to my ac millivoltmeter)
Im understanding that there is something wrong with the power supply between the bridge rec and the sens/output board. I just dont know how to diagnose it…
not sure where to go next, may try a chinese 15/0/-15 power supply and bypass the original cicrcuit completely, but i really dont wanna butcher the OG unit, it would be more of a temp fix to make some more records.
Any help greatly appreciated.
