I have one of the 3-S tech boards that’s been driving me crazy for a few hours.
Well, for starters, this DD amp was brought to me after someone else had already tried to fix it. I have spent considerable time checking and redoing all of the previous work. So now I only have myself to blame.
It looks like they did a partial repair on one bank of the high and low FETs and replaced the one IC on the driver board for that side.
The board is DWM3640NHV V30
The output section won’t oscillate. I replaced U1 and U2 and I also found that R21 was open and D2 was damaged. I went back with a 15v zenner for D2. Still I kept getting funky ohm readings across the cap on pin two (around 10k ohm range). Finally narrowed it down to the muting transistor Q6 is leaky. When I pulled the muting transistor my ohm reading on the cap on pin 2 went into the megohm region which is where it should be based on the other side. I carefully tested the transistor out of circuit and it tested leaky.
In Perry’s guide a 2SC3326 is mentioned as a suitable replacement but he had not confirmed it. Before a fire off an order for some I wanted to check if anyone else has confirmed that this is a good replacement.
Thanks Perry for your tutorial on these particular boards. Very helpful.
Thanks,
David
Well, for starters, this DD amp was brought to me after someone else had already tried to fix it. I have spent considerable time checking and redoing all of the previous work. So now I only have myself to blame.
It looks like they did a partial repair on one bank of the high and low FETs and replaced the one IC on the driver board for that side.
The board is DWM3640NHV V30
The output section won’t oscillate. I replaced U1 and U2 and I also found that R21 was open and D2 was damaged. I went back with a 15v zenner for D2. Still I kept getting funky ohm readings across the cap on pin two (around 10k ohm range). Finally narrowed it down to the muting transistor Q6 is leaky. When I pulled the muting transistor my ohm reading on the cap on pin 2 went into the megohm region which is where it should be based on the other side. I carefully tested the transistor out of circuit and it tested leaky.
In Perry’s guide a 2SC3326 is mentioned as a suitable replacement but he had not confirmed it. Before a fire off an order for some I wanted to check if anyone else has confirmed that this is a good replacement.
Thanks Perry for your tutorial on these particular boards. Very helpful.
Thanks,
David