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Hi guys, currently refurbishing 4 Pentas (2 Mk1 & 2 Mk2). I'm not using any B&O equipment to drive them so I want swap out the displays for some OLED ones and drive them from an Arduino board to put out a visual audio equalizer of what's playing. I have most of it figured out, however I cant seem to get the plug the OEM Display connects to, to feed out the 5v it should. I've been looking online and believe the the OEM Display waits for a signal before providing power.
Does anyone have any information / insight into the system and it's working? I just need 5 - 10v to power the hardware I'm using. I can achieve this through other means but would like to keep the speakers as OEM as possible and think I can work with what's here already.
Thanks
Alex
Only just checked the Mk.I manual - legs 2 and 3 in the DIN plug that goes to the display should carry 10v AC straight from the transformer which is rectified on the display board itself - something that should be easy-peasy to copy.
Hi there and thanks for the reply!
Lol i am honestly embarrassed, not even for one second did i stop to think that it might be AC power coming up the DIN cable, this is why i could not pick it up reading DC on my meter - what an idiot i am honestly. I will reference this against the Mk2 Manual too, although unfortunately the DIN connection at the AMP end is cut off on every drawing i have.
In any event i have 2 options now i guess, leave the OEM boards in place and take the Power from them or Get a small 10v psu and run some cables through the speaker myself.
My OLED Displays arrived as did the ESP32 control boards. Im going to be implementing something along the lines of this:
https://www.youtube.com/watch?v=RnVeXkrrnPI
However my screens are slightly higher resolution so the image should look a bit more polished.
Thanks again for your help its greatly appreciated.
Mk.II is the same (well, power wise at least)
Why not just get a 7805 and a couple of caps and make your own 5v supply for the Arduino?. Much more elegant that leaving the original board in there. Besides - I think you'll run out of room mighty fast if you leave the original in there.
Another thing you might want to consider (since you have them opened up anyway): If you plan on using them as front speakers in a surround setup more advanced than Dolby Pro-Logic*, you want to take a look at how the speaker turns the power amp on (pre amp is powered when there's power to the power supply). The Auto on/off is of course based on input, and that means, that in dialog scenes in movies (quiet ones), they WILL power down - and that is mightily annoying to say the least. What I did was basically remove the wires to the main relay coming from the built-in power switch module and hook it up directly to the 12v trigger from our surround receiver. It's not elegant, but I simply couldn't get the built in circuit to fire with the trigger signal from the receiver.
*Pro-Logic is basically two channels with center and surround matrix'ed in to the 2 channels and there will therefore always be some signal to the front speakers. With discrete channels, this is not the case.
Mk.II is the same mate:
And instead of leaving the old display in there, why not get a 7805 and a couple of caps (copy the supply straight from the Pentas perhaps?) and get 5v to feed the Arduino off. I think you'll seriously run out of room if you leave the original display in there.
Another thing you might want to consider now that you have it opened anyway: If you're going to use them in a surround setup with a signal above Dolby Pro-Logic*, the way the power amp switches on is going to become really annoying really fast. The Auto on setting on them, are, of course, based on them getting a signal, and with multichannel sound formats, and quiet movies or quiet passages with only dialogue, they WILL switch off. My solution, which is not very elegant, is to use the 12v trigger signal from the surround receiver to pull the power amp relay so always keeping it on. I'm not very handy with electrics - so I had to give up getting the Auto circuit to fire off of the 12v trigger signal. Some one smarter than me can probably tell you how to do it. - Don't worry about the pre-amp part - that is powered on whenever there's power to the power supply.
*Pro-Logic is a two channel signal with center and surround matrixed into the two channels, so there is always some signal coming to the speakers which will keep them powered on.
Hi Flerbizky! Thanks again for the reply! Your Mk.II Drawing is much clearer than mine, funny you should mention about the 7805 circuit!!! It was what i had found to be the most popular solution online when searching, the parts should be here today hopefully. Didn't manage to get anything done over the weekend so going to have a good look at everything tonight once everything arrives!
Regarding the Surround Setup, your right i was hoping to configure them exactly like that, i will look into the trigger, it might be out of my depth too! I wonder if there is a way to get the AVR to feed out some low level / in-audible frequency to keep them on.
Having the AVR feed a signal to the Pentas to keep the auto on/off circuit triggered sounds like an even worse solution than mine - sorry. Besides - if the signal you want to keep them powered on with is low enough to be inaudible, it's too low to keep them powered on. There has to be someone clever in here that can look at the auto on/off circuit and tell you within 7 seconds where to inject the 12v trigger from the AVR to activate it. Maybe create a post with that specific subject?
And I reckon the 7805 is the right way to go for power. We got trough a lot of those when I was an apprentice (at Bang & Olufsen actually) back in the days ;)
I will take your advice it's a bad idea and work with the idea you had!
I seem to have no time recently to get anything done on the project or the speakers :(
Well bit of an update, I finally got the 7805 Circuit setup, giving me a steady 5v DC which is great! However not so great is that is does not seem to be able to power my ESP32 & OLED :(
Might have to go back to the drawing board on this. Poking around on the other connectors that go to the LCD it seems there is 20v AC coming from somewhere, i wonder if this will provide enough current to get the Board & Display working, even though i have no clue why there is 20v there.
Another Update, the 10v Feed provides enough current when the speaker is actually playing, very bizzare, but also a relief. Now i need to get my coding hat on and get this Audio Spectrum going.
Sounds like a ground issue. A stock 7805 should happily supply 1.5A which should be more than enough for the ESP32 and the OLED. Can you do a quick drawing of your wiring?.
Cheers,/Steffen