Here we have an AU217 old model that in one case shows approximate voltages to expect during service which is not shown on service manual. As a former Sansui Authorised Service Center (1980~1990 steel city PA) I sort of remember some of the amplifiers service bulletin. This Amp used a 2SD188 and 2SB545 complementaries for outputs. Sansui used 2SD358 and 2SD528 as drivers. While it works, a service technician could substitute drivers by 2SA and 2SC type drivers.
Voltage reading at each transistor point approximately are as follows. Notice that I have used three 1N4149 type diodes as opposed to two 1N4148 often mentioned in various forum. Remember this Amp uses two DC rectifiers from the same AC source. For this design simplicity I have connected the Voltage Amp and output section to relay on the same DC power source. This unit has no DC offset pot but can be trimmed using R13.
What is you could not find the 2SB545 version or the 2SD188.
In this case you can easily modify the amplifier to use either NPN or PNP outputs only. You just need to rearrange a couple of components. See example below. I have done this for years, especially amplifiers that are heavily used in production, field music shows such as Bluegrass festival.
Here is an Example: -
All componet values are the same except I changed Q6 to 2SD188. Notice where I placed R41. It is now connected to the collector side of Q15. Q6 emitter and collector connection wires have to be reverces as well. That is it!
Voltage reading at each transistor point approximately are as follows. Notice that I have used three 1N4149 type diodes as opposed to two 1N4148 often mentioned in various forum. Remember this Amp uses two DC rectifiers from the same AC source. For this design simplicity I have connected the Voltage Amp and output section to relay on the same DC power source. This unit has no DC offset pot but can be trimmed using R13.
What is you could not find the 2SB545 version or the 2SD188.
In this case you can easily modify the amplifier to use either NPN or PNP outputs only. You just need to rearrange a couple of components. See example below. I have done this for years, especially amplifiers that are heavily used in production, field music shows such as Bluegrass festival.
Here is an Example: -
All componet values are the same except I changed Q6 to 2SD188. Notice where I placed R41. It is now connected to the collector side of Q15. Q6 emitter and collector connection wires have to be reverces as well. That is it!
