New Calrec M Series owner, hello

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Re: New Calrec M Series owner, hello

Postby jensenmann » Tue Jan 11, 2011 1:27 pm

You can get Sifam knobs in quantities of 10+ from their german distributor: sibalco.de
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Re: New Calrec M Series owner, hello

Postby Factory Street » Fri Apr 01, 2011 1:53 pm

Hello folks,
The desk has been serving me well now since the new year when I installed it.
It has been very reliable and more importantly sounds great.
I have it worked out now and it's great to work on, there's just one thing..........

There is a row of green knobs called PA, at first I assumed they worked just like the other auxillaries, however the difference is that they don't work even in "pre fader" mode if

A- the fader is at the bottom of travel (off)
B- the channel is not sent to a group
C- the group fader is a th the bottom of travel (off)

I'm guessing this is intentional as a way of easily muting the PA as the signal goes "off air"

What I would like to do is modify it to work in the same way as the other auxes to get another headphone mix out of it without messing about with faders and groups.
Any ideas?
I don't have any schematics but I'm pretty good at working things out if I know where to look.

Cheers

Alex
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Re: New Calrec M Series owner, hello

Postby DraytonTom » Mon Apr 11, 2011 3:16 pm

Hi Alex

I am pretty sure it is possible to mod this. The switching for the PA send is done with one of the 4053 ICs, Calrec got around the poor linearity of these ICs by turning the signal into a current and then converting it back to voltage at the bussing amp.
I am not sure exactly what sort of RC modules you have, mine are all RC1652s...
If you work backwards from Pin A 19 on the Euroconnector (Top connector as viewed from the front of the console) which is the PA bus line, you should find a 390R resistor, and before that the line should disappear into one of the outputs of the 4053 switch circuits. Theres 3 on a chip... the signal input side of that chip should be attached to a 5K1 resistor, and that in turn should come from the PA pot.
On the RC 1652 they are R79 and R78.
When you identify them on your module you need to work out a way of attaching the end of one resistor to the end of the other. You could do it with a piece of wire and then just hot glue the wire and the floating resistor ends down to the board for reliability.
you could just use one resistor valued at 5K6 the same as the other aux send bus resistors.
Alternatively you could fix the control input to the relevant 4053 switch so that it is permanently on.
I think the input is pulled high by a pair of 100K resistors which keeps it off and the PA switch bus line switches it low.
So if I have got that the right way round permanently grounding the 4053 control pin through a 100K resistor should keep it always on... for the 1652 grounding the other side of R81 should do it.
I think the first method would be less likely to cause any major issues, plus it saves your signal going through any extra circuitry.
The reason I had though about doing a mod to this part of the circuit was to make the PA a straight forward aux send, but use the IC switch for the PFL signal using the same logic control as the AFL. As I am building my own control section I was going to add the function to switch between afl and pfl signals routing to the monitor section.
Anyway, I haven't actually tested this yet, so please proceed with caution!

Cheers

Tom
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Re: New Calrec M Series owner, hello

Postby DraytonTom » Tue Apr 12, 2011 3:35 am

Hi Alex

Just reread my post. Talk about putting the cart before the horse!
If you ensure that the pa switch bus stays at the correct logic level. Then all the PA switches will stay on all the time.
That should consist of finding where the bus meets the logic controller and modding there. Much better than messing about with 40 odd modules.
Cheers
Tom
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Re: New Calrec M Series owner, hello

Postby Factory Street » Mon Apr 18, 2011 4:35 pm

Hi Tom,
Thanks all the ideas, great stuff.
Meanwhile I talked with Stephen Brant at calrec and he sent me a mod, I'm not at my email now so I'll share it later.
I do need to mod all the channels not just a master controller though it seems.
I have done one channel and that is working as I want.
I like the service from the company 23 years aftewr it was sold.
Cheers
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Re: New Calrec M Series owner, hello

Postby GJC Designs » Tue Apr 19, 2011 1:28 am

Factory Street wrote:I like the service from the company 23 years aftewr it was sold.
Cheers


A correction for clarification and accuracy.....

For virtually all of its almost 50 years existence Calrec has been privately owned. There was a brief tie-up with AMS lasting for a couple of years in the mid-1980's.

In 2007 Calrec was acquired by D&M Holdings, a US-owned audio-visual equipment provider.
Details of the news announcement are here:
http://www.yorkshirepost.co.uk/business/business-news/d_amp_m_holdings_takes_over_calrec_audio_1_2470622

Regards,

Gareth.
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Re: New Calrec M Series owner, hello

Postby Factory Street » Tue Apr 19, 2011 11:19 am

Hi Gareth,
I did mean after the desk was sold, not the company...
Cheers for the info though.
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Re: New Calrec M Series owner, hello

Postby Factory Street » Tue Apr 19, 2011 11:26 am

Here is the mod I was sent by Stephen.


"To disable the mixer's PA inhibit function you will need to modify the channel auxiliary send module (RC2225) and the group auxiliary send module (RG2226).

To modify the RC2225 please carry out the following:-

1) Remove one RC2225 module from the mixer.
2) Remove the module side covers. To do this you will first need to move the retainers at the connector end of the side covers. Once the retainers have been moved the side covers should side out.
3) Find IC7. When the PCB is viewed from the component side IC7 should be found in the top right corner. IC7 should be marked on the PCB screen print next to the chip. IC7 is a 3 way (A, B + C) CMOS switch (Device 4053) which controls the PA output of the channel.
4) Cut the track that goes to pin 10 of IC7. This will disable the switch firing line.
5) Link pins 2 and 15 of IC7. This is required because although the firing line is disconnected it is floating and could , albeit unlikely, fire by itself. Linking these pins means the switch contacts are short circuited and therefore always on.
6) Re-fit the module side covers.
7) Insert into the mixer and test. If the modification is successful, modify all the RC2225 units.

The modification for the group auxiliary router (RG2226) is identical, except that the CMOS switch is reference IC10, as oppose to IC7.

For additional information see the attached two page PDF document. One page is a section of the RC2225 circuit diagram, with the IC7B PA switch and page is more information on the 4053 CMOS switch IC."


I had a spare 5 mins the other day and just linked pins 2 and 15 on one module, I didn't cut the trace and the mod works as I want it to.
Does anyone think this will cause me problems? It shouldn't matter that the switch is still recieving it's firing signal should it?
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Re: New Calrec M Series owner, hello

Postby brianroth » Tue Apr 19, 2011 3:36 pm

It depends on how they are using the 4053 CMOS switch chip within the circuit...I don't have a schematic to refer to. I would follow the instructions given.

Best,

Bri
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Professional audio system design/service/custom equipment
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Re: New Calrec M Series owner, hello

Postby Factory Street » Wed Jun 08, 2011 7:48 am

Hi folks,

Anyone know how to get the bulb out of the square backlit buttons?

Cheers
Alex
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