Hi folks. I have a friend's Dayton Audio SA1000 subwoofer amplifier on the bench. It puts out very little amplification regardless of input level and/or gain level settings. It also starts distorting once input or gain is increased moderately.
Hoping for some guidance and/or documentation. I can't find a service manual or schematics for this thing which is a hurdle for my level of knowledge and skills.
FYI - I am not a business, just trying to help out a friend.
Hoping for some guidance and/or documentation. I can't find a service manual or schematics for this thing which is a hurdle for my level of knowledge and skills.
- It maxes out at 7 volts AC as measured at the speaker terminals into an 8 ohm load using a 50 Hz sine wave input from a pre-amp.
- The only component that gets hot is a resistor (labeled R19) which measures 218 ohms. Looks to be 2 watt size. It is visually browned from heat.
- Capacitors all look ok visually and are of the 105 degree spec. On the older revisions capacitors were a problem per forum searches.
- DC rails are +/- 137 VDC. There's approx 4 volt sawtooth riding on the negative rail, and approx 1 volt sawtooth on the positive rail. Of note, the main circuit board has 165V silkscreened where the power supply wires connect, so wonder if the +/- 137 volts is a symptom to explore.
- The qty 3 of 18 VAC power supply lines all measure at 19 VAC
- The 15 volt points on the boards measure +14.8 and -14.8 VDC
- The output transistor's junctions measure ok with a multimeter. (Qty 2 of TTC5200 and qty 2 of TTA1943)
- There are many FET's of which I am uncertain their junction condition.
FYI - I am not a business, just trying to help out a friend.