Testing Procedure once boards are assembled:
-first, make sure to wire up the fuse and AC terminals correctly. Test with a multimeter set on ACV to make sure that your switch works. Wire from the AC H terminal on the AC socket to a fuse holder, and then into a switch.
-connect the first wire of the transformer primary to the AC H connection on the power switch
-connect the second wire of the transformer primary to the AC N connection on the ac input terminal.
-connect the earth ground from the ac inlet to the main chassis ground
-for US or other 120v countries, if your transformer has dual primaries and is specified for either 115vac or 230vac, such as the Avel Lindberg common transformers, wire both the pairs of primary parallel with each other.
Here is a picture of the Avel Lindberg transformer wiring:
-For the Avel Lindberg transformer in the US, connect the Blue and Violet wires to the AC H connection on the switch, and the Gray and Brown wires to the AC N connection on the AC input terminal. For 230vac, connect the transformer primaries in series, as shown in the above image.
-Make sure to isolate the secondary wires from the transformer, and power up the amp to verify the voltages from the transformer secondary windings. If you have a 2x18vac transformer, you should now measure 18vac across each secondary (secondary 1 = black/red and secondary 2 = Orange/Yellow)
-power off the amp, and wire the secondary windings from the transformer into the AC1 and AC2 terminals on the power supply board. Here is a picture:
[IMGDEAD]http://www.chipamp.com/diyaudio/lm1875-7.jpg[/IMGDEAD]
(AC1 = black, AC1(bar) = red, AC2 = orange, AC2(bar) = yellow)
-Wire one of the GND connections on the PSU board to the chassis ground.
-Once the transformer secondaries are connected to the PSU board along with the chassis ground connection, power up the amp to check the output DC voltages. Measuring from GND to V+ and from V- to GND should show ~25vdc if you are using a 2x18vac transformer.
-The LED on the PSU board should also be lit up, if installed correctly.
-Once the power supply voltages are verified, power the amp down, and wire up one amplifier board to the V+, V- and GND connections from the PSU board to the amp board.
-power up the amp again, and check the DC offset of the amplifier with the multimeter, by setting it to the minimum DC voltage setting, and measuring from OUT to OG. You should measure between 10-30mV, but under 100mV is acceptable.
-if all checks out, power down amp, and hook up the other channel and test it.
-once both channels are verified, connect the RCA input terminals to the IN and SG connections on the amp boards for both channels. Also connect the OUT and OG connections on the amp boards to the output terminals on the chassis.
-power the amp up again, and test the amp with a test speaker for both channels.
-Once all is verified, connect to your system and enjoy!
(note, this is a quick rough draft of the manual, and I will work this into a manual for putting together an LM1875. Let me know if you spot any issues, or have any comments)
--
Brian
