Calrec MU2279 - BBC Stereo PPM board

[tonzauber]

Dear wise minds of Groupdiy,

for my mixing desk project, I would love to use a beautiful BBC-Style Stereo PPM meter as the Master meter.

It comes with a Calrec MU2279 board strapped to its back, which is the meter driver.

Now of course if you type "Calrec MU2279" into google, something rare happens: Google finds no search results whatsoever.

There is a series of soldering pins at the bottom of the board.

leftmost three pins, labelled  "+  CR  - " seem to be the DC power supply  -  but what Voltage?  12V? 15V? 18V? 24V?

Then there seem to be the pair of  Inputs, T/P1 and T/P2

And then some M/S Switching.

I suppose CR means something like 0V or Common Rail.

Can anybody help me with the proper supply voltage needed?

Thanks

Georg

 

[tonzauber]

and the connectors in detail:

 

[gyraf]

Yes, CR is clearly Ground/Reference/0V

Usually Calrec is +/-16V, with a +8V for logic/light that is actually hanging at -8V from the +16V-line

Maybe look at MU3801 (from M3 desk) for inspiration?

Jakob E.

 

[NOON]

Looks like your T/P 1 and 2 are I/P 1 and 2 with the bottom trimmed off, so definitely inputs. The circuitry they lead to looks like input circuitry at a quick glance too. 25V caps at the PSU inputs and TL072s indicates a max of +/- 18V.

 

[tonzauber]

Thanks guys!

I hooked it up to my 12DC supply and, as no smoke was immediate, applied some signal to the inputs.

It swings fine up until 4, but then I guess the voltage is too low to drive it higher. I can make it overshoot up to five, so the movements are not jammed.

I will try with a higher supply voltage - just have to wait for my dc/dc converters.

Thanks

Georg

 

[PRR]

> my 12DC supply

Doesn't it want plus-and-minus supplies, not single supply?

 

[tonzauber]

ah damn... How i hate symmetrical power supplies.

 

[tonzauber]

I built a makeshift symmetrical supply out of a 24V ps and a voltage divider..... it works now full swing.

Only illumination is not working (the LEDs most probably miss the few Volts more than the meter itself), so i'll re-engineer that

I rather keep any DC/DC converters out of the mixing desk case.

Thanks PRR for the kick in the right direction.

Georg

 

[pvision]

Is it a coaxial PPM? Those movements were extremely expensive.

What colour are the needles? White / yellow are sum / difference and green / red are left / right

Nick Froome

 

[tonzauber]

Hi Nick,

Yes, these are the good Sifam coaxial meters.

I know they were super expensive, but I could score two on Ebay for 80GBP - one has the driver board, the other one is just the meter.
Both have orange/green needles.

I love these BBC meters, as they are both accurate and easy to read. As a continental European I just have to get used to the scale.

This is the meter with a new built led illumination: