Converting a B&K Receiver to a Power Amp

[MTAtech]

I’m trying to convert my B&K AVR 307 receiver to a seven channel power amp. You may ask, why would I want to do this? Well, the AVR 307 was a top receiver five years ago. However, in the fast-moving world of new formats and connections, the AVR 307 is obsolete. However, its amp section is still first-rate (150w/channel x 7.)

One can see from the picture below how massive the amp section is:

My theory is that by finding the place where the pre-amp board connects to the amp, I can separate that connection and install RCA inputs to feed the amp directly.



Note the markings, such as "RF" (Right Front), "LF" (Left Front), "CF" (Center Front), etc.

Not ever doing a project like this, I don’t know whether the green or blue wire goes to the center of an RCA connector or the outside. I also want to use similar modular connectors – in case I ever wanted to return this to a receiver. However, I have no idea where to get those type of connectors. I already purchased the same blue and green wire that B&K uses (Brand=Spectrum.)

Any guidance is appreciated.

[MTAtech]

Anyone know where I can get matching male connectors, as shown in the last photo? They are 5-pin. I think they are called Molex connectors, as per the schematic that I have.

[ostripper]

Those blue/greens are the amps outputs, not the inputs.
OS

[MTAtech]

Originally posted by ostripper
Those blue/greens are the amps outputs, not the inputs.
OS

I find that hard to believe since different blue/green wires, from the amp boards (on the sides,) lead to the speaker terminals.

But I'll double check to confirm.

[ZepOfLed]

After having seen my thread, you know that I am trying to get it running without the preamp section attached at all. This will be very helpful though that your unit is in perfect working order. Do you have a multimeter to test some voltages for me?

Another member, Iain Mcneill, posted on my thread and is trying to help me sort things out. I don't have time to post the full details at the moment, but if you want to also get the amp running without the preamp, these tests may benefit both of us. Basically we want to compare the voltage in the orange "CTRL" lead in various states to see what effect it has on the operation of the amp modules. I'll be posting more later tonight. If you want to, you can read what he has posted more recently on my thread to get an idea of what I'm talking about.

[MTAtech]

Yes, I'll cooperate to our mutual benefit.

[MTAtech]

I have a multimeter but need more direction regarding tests.

[ZepOfLed]

Hello again MTA,

For staters, we need to see if the voltage on the "CTRL" lead changes depending on if the amp is activated or not. Lets go about this very carefully...

Take a look at the power supply board. On the left side (looking from the front) there are groups of three wires leading from the power supply board to the amp modules. 3 wires per amp module. A red wire (V+), a black wire (V-), and an orange wire (CTRL).

~~~~~~~~~~~~~~~~~~~~~~~~~~
*For each measurement:

-Set your multimeter to Volts DC, the the next step above 65V (mine is 200V).

-take the black lead and place it on a ground terminal, labelled "GND" (there should be a green wire coming from it).

-place the red lead on the terminal of one of these orange wires on the power supply board.

-read it

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
*Take the above measurements when:
-the amp is in sleep/standby
-the amp is powered on (with no music playing)
-the amp is powered on (with music playing)
-any other unique power settings you can think of

Record voltage measurements for each of these and let me know what you get. I have no way to test this, as my receiver no longer operates normally. Hopefully the change in voltage of the CTRL wires will tell us something about their usage.