Not knowing how they did the mods physically is my only concern. Was the PCB hacked or not. Comparing the two schematics it looks as though no traces had to be cut. The normal bias circuit is just two resistors and two 5K trimmers per channel, the "B" version has two resistors, two 100K trimmers, four xsistors, and two diodes. There is not much space in a NINE so I'm not exactly sure where these parts were installed and if the transistors were for thermal tracking. I guess it really doesn't matter as all of it will be gone. Schematics are on the way ASAP.
Craig
Craig
What docs do you want/need?
Since this thread began I picked up a dead NINE+, regular version. Found blown fuses, the - regulator bad in one channel, a shorted ceramic capacitor, and several leaky ARC output transistors. Another thing that amazed me on the power supply PCB, all of the solder joints for the power xfmr output secondary leads were broken and just had to be intermittent. The secondary leads are very stiff mag wire. Looks as though the insulation coating wasn't removed before somebody attempted solder them.
Rebuilt the main power supply, rebuilt the individual channel regulators, and replaced all 20 output transistors with MJ21194s.
First attempt at setting the idle current I couldn't get to 1A. Replaced R14,29 (1kOhm) with 300 or 330 Ohm resistors and now there's plenty of adjustment left when set to 1A across the fuses.
Craig
Since this thread began I picked up a dead NINE+, regular version. Found blown fuses, the - regulator bad in one channel, a shorted ceramic capacitor, and several leaky ARC output transistors. Another thing that amazed me on the power supply PCB, all of the solder joints for the power xfmr output secondary leads were broken and just had to be intermittent. The secondary leads are very stiff mag wire. Looks as though the insulation coating wasn't removed before somebody attempted solder them.
Rebuilt the main power supply, rebuilt the individual channel regulators, and replaced all 20 output transistors with MJ21194s.
First attempt at setting the idle current I couldn't get to 1A. Replaced R14,29 (1kOhm) with 300 or 330 Ohm resistors and now there's plenty of adjustment left when set to 1A across the fuses.
Craig
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