Calrec Cm 102s (Vt Edit mixer) - schematic\service manual needed

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dunk91

Member
Joined
Jun 11, 2016
Messages
20
Location
Italy
Hi everyone, I'm using this wonderful little mixer since a couple of years and I really love it.

I'm actually refurbishing it and a channel schematic\service manual would be more than handy to have, as channels boards have a few trimmers wich I can't understand what they set.
Also PFL seems to be pretty obscure, as I can't find a way to monitor it (pinout doesn't show any output pins for PFL\AFL bus).

Now the sad part.

I've contacted Calrec, wich sent me all the pinout and blocks drawing (wich I've already obtained from previous owner) but according to them the original schermatic has been lost from their archives and they can't provide me any further info about manteinance routine and PFL operation.

I know for sure that the schematic PDF is floating somewhere on the internet, as it was included in a past ebay auction regarding a few channels removed from one of this mixers, but all that's left is a miniature of the PDF schematic, wich is microscopic and unusable ( you can check it here https://thumbs.worthpoint.com/zoom/images4/360/0612/25/calrec-qr2767-stereo-input-line_360_d7edd54fbfebc54839e6623ea84cb331.jpg)

Channels are QR2767

So long story short, if anyone knows anything about this mixer's PFL, and has a schematic or even better a service manual to share, I will be forever grateful.

Emanuele.
 

chrisregent

Active member
Joined
Dec 21, 2013
Messages
26
No circuit diagrams I'm afraid but PFL is normally straight forward as an an output.

just follow the pfl button to the edge connector on a channel and then look at the master modules to see which one takes the pfl bus up onto it to an opamp input and then off the an output...
On the channel the switch may control a 4053 to switch the audio (a popular Calrec design) but just follow the logic to the IC read the datasheet for the pinout and switch then look at the pins it goes to on the 41612 connector.

Don't twiddle pre-sets unless there is a specific thing to adjust. Replace all the electrolytic caps first then measure it. Twiddling presents before replacing caps and testing everything normally causes issues. the number of "repairs that I have seen from people maxing out pre-sets is TO HIGH. haha measure first, repair, measure again.
 

dunk91

Member
Joined
Jun 11, 2016
Messages
20
Location
Italy
Hi Chris!

I've already managed to get the PFL/AFL working, it was disabled on the monitor module. I've found 2 traces cut on the board and 1 pull down resistor on the enable trace to keep the pfl monitoring from switching up. Removed it, restored interrupted traces and everything works as it should.

Also I've reversed the blocks around the trimmers and found what they set.

VR8, VR9: set the post pan\width unity gain.

VR12, VR13: set the post fader global gain. I've adjusted them to have the same level between PFL and AFL with fader fully open.

VR10, VR11: trim the symmetry on the dbx 2150 vca, I've adjusted them to trim away all the 2nd harmonic.

VR14: it looks to inject a CV on the negative control ports of both 2150 vca, can't figure out why it is needed so I've left it untouched. Any input here is welcome, just for the sake of learn things  ;)

Of course trimming is done after recap!


chrisregent said:
No circuit diagrams I'm afraid but PFL is normally straight forward as an an output.

just follow the pfl button to the edge connector on a channel and then look at the master modules to see which one takes the pfl bus up onto it to an opamp input and then off the an output...
On the channel the switch may control a 4053 to switch the audio (a popular Calrec design) but just follow the logic to the IC read the datasheet for the pinout and switch then look at the pins it goes to on the 41612 connector.

Don't twiddle pre-sets unless there is a specific thing to adjust. Replace all the electrolytic caps first then measure it. Twiddling presents before replacing caps and testing everything normally causes issues. the number of "repairs that I have seen from people maxing out pre-sets is TO HIGH. haha measure first, repair, measure again.
 

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