1975 Allen & Heath MOD2 Rebuild Project

I found the attached. MOD2 Series 3 Output Modules allow for sync monitor signals between main and aux input (monitoring).  But the output modules that I own do not have the sensitivity presets that are shown on the layout...  I will need to see if the amplifiers match the drawings or if there is a '3' somewhere on the board.

The PDF you attached doesn't appear to show anything to do with the relay supply.

Another possibility occurs to me now - the resistors on the bottom could have been a quick repair method. If the 1w 100R on the board had failed it may have been more convenient to simply bypass it by soldering those resistors onto the edge connectors than to pull the module out and replace the original resistor. It might be worth testing the resistor on the board - just a thought.

This project is way over my head in regards to my knowledge of electronics. There are other things I want to work on and quite frankly this is taking up too much space. I'm considering parting this out, PM me if you're interested!

WOULD LOVE TO SEE SOME UPDATES ON THIS!!
I got #41  MOD2 which has 4 mod 1 channels!

Glad to hear this.  I am not certain, but I think the channel strips that someone hacked up in the link below are MOD1.  They have the inductor EQ.  I shelved my MOD2 project when I moved, will be getting back to it soon.  What is the configuration of your mixer?


http://www.ebay.com/itm/VINTAGE-ALLEN-AND-HEATH-RACKED-CHANNEL-STRIPS-TRANSFORMER-COUPLED-DISCRETE-/281509202183?pt=US_Live_Studio_Mixers&hash=item418b418907

16 channels 8 buss
but I'm trying to figure out it it 16:8:2?
The board is being recapped and cleaned up etc so I don't have it here..we haven't powered it up
But that doesn't look like Mod-1 channels

I don't think it's 16:8:2 but instead 16:8
I have MOD3 and from what I know MOD series has no "master". It's 8 independent outputs of which first two are mirrored to the center section and fed to a control room output (unbalanced!). That was the era of 8-track tape recorders, remember!

There was a limited discussion not too long ago about adding 2 buss function to the MOD2 /MOD3 mixers. 
See the following:

http://groupdiy.com/index.php?topic=33038.msg654684#msg654684

The mirroring wires that Shot talks about are located underneath the heavy metal connector panel.  Here is a photo.

MOD2 wiring schematic...

yes it's a 16:8
I'll probably mix out of bus 1 and 2 to start but having a summing mixer after would allow me to do multi bus compression.
I have all the documentation I could scrounge online but if anyone has a real set of schematics for the mod2 or 3 I would appreciate it. It will speed up the process of getting this up and running.
who ever took this out of commission just cut the harness. Nothing marked and no wire going to the vu meters...
thanks in advance.

These consoles probably should have had connectors on the wiring bundle from the main frame to the meter bridge, but that's one way they cut costs back in the day.

A screened wire takes the meter signal from each output module connector as shown in the annotated photo. This is a photo of the underside of the fame.  Each meter signal wire is soldered to a meter buffer pcb card located on the meter itself.

Did they cut the wiring from the frame to the patchbay too?  If so, this will be a much more serious problem to fix so you have access to aux buss,  direct outputs, etc.

Can you post some photos?

Hey all, The screws that came with my mod 2 are not right and the strips are not being held down so I'm getting a lot of intermittent noise if I touch the console too hard.
Where can I find the correct screws........I'm guessing they're B. A, so I have to order a bunch from England
just need to know what to order...thanks!!

This place is located in the USA between Rochester and Syracuse.... they carry BA type machine screws.  Maybe you could get some  samples to try? 

http://britishfasteners.com/

Finally got my mod 2 installed  but the repair guy misplaced the original screws to hold down the channel strips etc.
Any one know the spec and where I can get these.
apparently their B.A. and only available in England


thanks!

Does anyone have specs on the monitor potentiometer??
I would love to replace this with a higher end pot that  doesn't skew the mix at lower volumes

Looks like that pot is a dual 4K7B potentiometer.  Schematics are located in the tech bullitens forum under Allen & Heath.  Attached is the Monitor Section Board B schematic.

thanks!

Ok , I love the sound of this console........there I said it.
I need to take this apart again and spray the crap out of the push buttons..they are intermittent.
I'm taking the rails off that hold the screws and changing them with an old sound craft 200 that's sitting in my attic. Too many are stripped.
also having a big noise problem when I bring protools back in to the tape monitor section. Big hum there. Any ideas?
I think the power in my room is noisy, I tried the ground lift thing but no luck.  I'm using it as a monitor and summing mixer , getting the i/o's thru Pro tools hd and my patch bay . Tried the echo/aux sends but that was super noisy.
thanks

Could this be an impedance matching problem with the noise?  What is your Protools interface?  Protools output impedance?

Attached is the MOD2 specifications for line input.

Hey did you get your mod 2 working??