Samson Aura D415

[bsco]

Good day to everybody.....I have this unit here and when powered up there was a very loud buzzing sound coming out of the woofer......did some checking and decided to pull the two Sanken chips out.....and disconnected the speaker....85V dc on the output pins....pulled the two mosfets and the dc offset dropped to approx 18Vdc......started poking around again........found R41 which when I tried to desolder it, one of the leads came right out of the board....the lead had snapped off underneath the body of the resistor.....R41..(180 ohms) is radial type......SO, I tacked to 330 ohm/2W resistors(measures around 166 ohms) in parallel and now I have 18 mV offset on the woofer connections and only a couple of mV offset on the horn connections.....is this imbalance being caused by the 166 ohm resistance......I will get a 180 ohm 2W resistor in the next few days and then install it in the board....then install the 4 transistors back in....if anybody knows off hand what the bias voltage has to be set at, that would be a help...The schematic is posted below........
Cheers
Auro_D412_D415_HF_AP&power_v1.41.pdfAuro_D412_D415_LF_PA_v1.3.pdf

[Jazz P Bass]

I take it R 41 is on the first schematic.
The power supply.
R41 feeds the negative voltage regulator.
Hard to imagine how that would affect the dc offset on the speaker terminal.

[bsco]

I take it R 41 is on the first schematic.
The power supply.
R41 feeds the negative voltage regulator.
Hard to imagine how that would affect the dc offset on the speaker terminal.

I thought I had posted the correct section..... sorry about that.....anyway, when I subbed in that 166 ohm setup, the dc offset dropped right down....I guess with one of the voltages being missing, it upset the driver circuitry somehow...I will install the correct one when I get it and then re-check....then I will install the output transistors, and check for dc offset......I'll post my findings here....
Cheers
Sorry about that...I did post the correct pages.....my mistake....it has been a long day....
Another EDIT.......the VCC- goes to the base of T5 on the power amp section....so I guess with that voltage missing, T5 is shut down and throws the bias setup off.....

[bsco]

Good morning...back at this one again....ordered the proper resistor, R41 for this one....180 ohms/2 Watts....Installed it and output transistors, no speaker connected, the dc offset is now measuring only 16mV....does anybody know what the bias voltage is supposed to be?? there is no value on the schematic......maybe 16mV is fine for a dc offset but it would be nice to find out for sure......any comments greatly appreciated.....
Cheers

[Jazz P Bass]

16mV is fine for a dc offset

[bsco]

16mV is fine for a dc offset

Thanks Jazz....Much appreciated....I'll re-assemble and give it a good check out....
Cheers

[bsco]

Reassembled and tested it...works great.....owner will be very happy...Thanks to everybody for the help.....
Cheers