mac

Racking Channel Strips Audio Developments UK New
« on: June 18, 2009, 12:32:33 AM »



Can anyone identify the console that the channel strips may be from in the attached photos?
 
Problem is no-one can seem to identify them, so no schematic, and few clues to go on.

Each input channel has phantom and phase switch followed by rotary gain pot, EQ stage, FB and Echo sends then finally Pan, Solo and Ch switches, Pan pot, Sends Buttons and a 100mm fader. There are six ML748CS ic’s on board each input channel strip and a mic input tranny which has “MSC 1829 PMT\7710” written on it.
No other markings or identification.

So far I have spent several hours with a DMM tracing the circuits that relate to each of the connectors on the bottom edge of the PCB where it obviously sat in the input slots of the console. Also, have started to make a collection of schematics from other desks from the late 70’s early 80’s to see if I could start to see similarities in the circuits from which to make some assumptions about the pin outs on my strips (have noted some similarities in parts of the circuits from a Series 20 Cetec input channel schematic).

The goal obviously being to try to determine how to commence making connections to bench test these strips, and ultimately rack them up once I am happy with them.

I have a rather poor attempt at a sketch attached which is as far as I have gotten with my detective work. I realise that it isn’t a proper circuit diagram and probably won’t make sense to all knowledgeable folks around here – as stated I am still learning how these things go together, (and how to draw circuit diagrams). If you can see anything obvious in terms of pins which would likely be inputs, ground, power feeds etc that would be appreciated.

I started with all the easy and obvious stuff like 48v phantom feed to the switch, grounds on all the pots, sends and group assign feeds from the switches. What really has me scratching my head is pins 1-3 as they tangle with the mic input tranny (which I also have no info on).

I am assuming that a second power feed like maybe 15v+ and 15v- comes onto the board at some point, but this isnt obvious to me yet. I cant locate a datasheet for a ML748CS, however I did locate a modern "replacement" IC for the ML748CS which is a NTE975. This chips datasheet identifies pin 7 as V (+) 15v.

Any insights would be appreciated.
Cheers, Mac.
 ;D
« Last Edit: March 03, 2011, 03:19:32 AM by mac »
Barclaycon: The client said 'That sounds great, what are you using on it?'
The engineer's reply was: '30 years of experience'.


mac

Re: Identify old console Channel Strips
« Reply #1 on: June 18, 2009, 12:34:21 AM »
Just realised, I forgot to state that the seller on ebay advised that he thought the strips were from a custom made desk possibly out of Nova Sound or JANDS from Melbourne or Sydney in the late 70's early 80's.

thanks,
Mac.
Barclaycon: The client said 'That sounds great, what are you using on it?'
The engineer's reply was: '30 years of experience'.

jdbakker

Re: Identify old Nova Sound or JANDS ??? console Channel Strips
« Reply #2 on: June 18, 2009, 09:38:02 AM »
I cant locate a datasheet for a ML748CS

I would not be very surprised if that were a second source for the LM748, which is a 741 with external compensation. Another second (third? nth?) source is the ST UA748, which is still available from Digi-Key.

There are various creative games that can be played with that compensation pin (other than straight compensation), which makes replacing a 748 with a more modern op-amp a bit of a tricky proposition without looking at all surrounding parts.

JDB.
« Last Edit: June 18, 2009, 09:40:07 AM by jdbakker »

mac

Re: Identify old Nova Sound or JANDS ??? console Channel Strips
« Reply #3 on: June 21, 2009, 05:47:30 AM »
Hey thanks JDB....
 :)

Mac

Barclaycon: The client said 'That sounds great, what are you using on it?'
The engineer's reply was: '30 years of experience'.

astrovic

Re: Identify old Nova Sound or JANDS ??? console Channel Strips
« Reply #4 on: June 21, 2009, 06:34:06 AM »
Hey Mac - perhaps try posting this at the Turtlerock Mastering forum - there's a bunch of Aussies there that are building up some fair knowledge concerning Aussie studio gear, so you may get some joy there.

Cheers

mac

Re: Identify old Nova Sound or JANDS ??? console Channel Strips
« Reply #5 on: June 24, 2009, 06:57:21 PM »
Hey Thanks for the tip Astrovic. I have registered over there at Turtlerock but still waiting to be confirmed as a member so i can post. (Has been about a week now).

I have also emailed Jands and Nova - but havent gotten any responses.

Do you have any other suggestions of where to take these queries here in Oz? There must be a big box of 80's live sound engineers hanging out somewhere that would know these things!!!

I am at that stage of having two many unfinished projects, that I cant seem to move forward on at the moment and it is driving me nuts.....

Cheers,  ;)
Mac.
« Last Edit: June 24, 2009, 07:00:29 PM by mac »
Barclaycon: The client said 'That sounds great, what are you using on it?'
The engineer's reply was: '30 years of experience'.

astrovic

Re: Identify old Nova Sound or JANDS ??? console Channel Strips
« Reply #6 on: June 24, 2009, 11:32:56 PM »
yeah, a couple of suggestions would be to contact either Rob Squire at http://www.proharmonic.com/

or Joe Malone at jlmaudio.com

Fair to say they know their stuff re: Aussie audio gear.

If you're having a struggle getting up and running at Turtlerock, I'd be happy to make a post there directing the locals to this thread.

mac

Re: Identify old Nova Sound or JANDS ??? console Channel Strips
« Reply #7 on: June 25, 2009, 04:22:05 AM »
That would be much appreciated ....thanks

Mac...
Barclaycon: The client said 'That sounds great, what are you using on it?'
The engineer's reply was: '30 years of experience'.

astrovic

Re: Identify old Nova Sound or JANDS ??? console Channel Strips
« Reply #8 on: June 25, 2009, 07:01:00 AM »
Done  :)

damieny

Re: Identify old Nova Sound or JANDS ??? console Channel Strips
« Reply #9 on: June 25, 2009, 08:05:06 AM »
mm nova knobs, nova style cct design.. but i dont recognize the console.. does it have a jaguar (as in the car) logo in the cct board anywhere..

or initials like JMc JM, JV, GN?

i used to work at nova and fixed a bunch of consoles, but i dont know this one...

damien
« Last Edit: June 26, 2009, 09:36:24 AM by damieny »


mac

Re: Identify old Nova Sound or JANDS ??? console Channel Strips
« Reply #10 on: June 28, 2009, 11:45:24 PM »
Hey Damien,
thanks for your thoughts, sorry on the slow reply.... No I cant see anything Jaguar...no logos or marks.

Apart from the info at the top of the thread the only other markings beyond individual component markings is a serial number sticker on each strip reading A5561, A5562, A5565, A5567.

Appreciate your input. Mac...
Barclaycon: The client said 'That sounds great, what are you using on it?'
The engineer's reply was: '30 years of experience'.

damieny

Re: Identify old Nova Sound or JANDS ??? console Channel Strips
« Reply #11 on: June 29, 2009, 03:20:18 AM »
call ian rumbold in melbourne. he may know. it looks like there is a logic board. there is the digital dipsllay thingy near the buss switches. im not aware of nova ever doing this. so im guessing jands.

mac

Re: Identify old Nova Sound or JANDS ??? console Channel Strips
« Reply #12 on: June 29, 2009, 04:00:05 AM »
Thanks a lot. Sorry for my ignorance but how do I contact Ian Rumbold?

This is getting confusing...Rob at Proharmonic emailed me today and said that it doesnt look like anything Jands he knows based on the circuit, switches etc.

So now I am really confused??? Perhaps I have sent us on a wild goose chase and this desk isnt even Oz made??

These things have Allen-Bradley "mod pots". Five 73a1's on each strip.
Does anyone know when these were produced (I understand from other discussions in the lab that these are no longer in production).
Maybe this will help to at least start to narrow down the production period...

cheers, Mac.
Barclaycon: The client said 'That sounds great, what are you using on it?'
The engineer's reply was: '30 years of experience'.

damieny

Re: Identify old Nova Sound or JANDS ??? console Channel Strips
« Reply #13 on: June 29, 2009, 04:23:11 AM »
maybe its a Holden from NZ? i think noel  anthony from top end sound in townsville had one (his was brown or black),,

ian rumbold 03 9419 3251

 

ritz

Re: Identify old Nova Sound or JANDS ??? console Channel Strips
« Reply #14 on: June 29, 2009, 06:32:12 AM »
Hello hello...

I've got a bunch of these channel strips too (also aquired from the same seller on ebay as mac's strips). This is basically what I have on them so far:

Each strip uses six 748 opamps. From my not-too-indepth poking around I'd say one is used in the mic preamp stage, two in the EQ stage, one each for 'FB' and 'Echo' outputs and the last one for the main output stage. As has been mentioned elsewhere, these 748 opamps are like a 741 but with external compensation. Indeed, each chip has an adjoining 10 (pF?) compensation cap between pins one and eight.

From the date stamp on the opamps, this thing looks to date from 1974.

Each channel strip has an input transformer labelled “MSC 1829 PMT\7710” as mac has already noted. I'm pretty sure these are Australian-made Trimax transformers as the "MSC 1829" part is a labelling scheme that matches other similar Trimax transformers of this type (the "MS" designating "Multi Shielded"). The "PMT" part, I'm quite sure, stands for "Pole Mount Transformer" (another label I think I've seen associated Trimax transformers before).

EQ-wise, there's a HF, LF and swept mid control. The mid control is inductor based. Gain control is a stepped rotary contol rather than a smooth turning pot.

Regarding the digital display next to the buss assign switches, there's actually no logic control involved. The seven segment LED display is used purely as an LED array. It looks like pressing different buss assign buttons switches in and out different combinations of LED segments on the display, thereby changing the reading on the display.

Also as mac noted, the pots are Allen Bradley mod pots. I believe the original A-B designated pots are no longer in production, but an identical type exists in the Clarostat Series 70 Mod-Pot. The pan control is a "regular" type ganged pot, also by Allen Bradley. The channel faders are made by Ruwido. They're an open frame type (and also pretty dirty) but have a nice, solid feel to them. Travel of the fader is unfortunately only 75mm.

I emailed Jands about these and this is what David Mulholland of the company had to say:
I don’t recognize these strips. The mixers we made, in this period, generally had anodised aluminium panels that were coloured red / green / blue / black. We almost always silk screened ‘JANDS’ somewhere on the metalwork and on the circuit boards.
Sorry I don’t have any suggestions as to who manufactured this one.

So yeah, they're not Jands channel strips.

As far as markings go, outside of the control markings, there's nothing to be seen anywhere, both on the PCBs and the face of the strips.


mac

Re: Identify old Nova Sound or JANDS ??? console Channel Strips
« Reply #15 on: June 30, 2009, 03:46:39 AM »
Hello Ritz,
Awesome to hear from a knowledgeable contributor. Thanks for sharing your info on these. I have spent several hours running test signals and measuring with my multi-meter and I think i have these almost figured out.

I think from the circuitry one of the red herrings which threw me off the scent for a while was my assumption about phantom power (as referred to in my first post).The on / off switch doesnt make sense as a phantom power switch, (because it doesnt feed the mic input) but seems to be a power feed to each pin 7 (+v) on the two EQ and main output opamp. From this I am now assuming that this is actually a switch to power up each strip (which seems a bit odd).

I hope that last sentence made sense. I am almost at the point where i am feeling brave enough to start feeding some voltage into one of these and test whats going in and out of each of the opamps. I am pretty much out of multimeter tricks. I was going to start at about 9v and see how it reacts. The new equivalent 748 opamp datasheet indicates + & - 15v requirements on pins 7 and 4, so I was thinking to slowly power these up and measure along the way.

One good thing from spending so much time on these strips with a multi,....one of my strips had a very ominous looking cross in permanent marker on it, which looked all the world like a tech had pulled a non working channel. During my tests i discovered on this strip a PCB trace which had a lifted pad and was not passing signal - quick dab with the soldering iron and it is now behaving like the other three.

I will post a picture of my current understanding of the pinouts later tonight hopefully...

cheers, Mac.
Barclaycon: The client said 'That sounds great, what are you using on it?'
The engineer's reply was: '30 years of experience'.

ritz

Re: Identify old Nova Sound or JANDS ??? console Channel Strips
« Reply #16 on: June 30, 2009, 06:26:30 PM »
Hehe... well “knowledgable” is probably debatable, but thanks.  :P
It looks like you've made some pretty significant inroads yourself into getting these things figured out -much more than I have. I haven't really had much time to nut these strips out in any detail (and probably won't have much time to do so 'til later in the month), but so far I've just been trying to search around to find the manufacturer. Haven't had any luck as yet, other than to rule out certain manufacturers (such as Jands). My plan for these strips is actually to set them up as a little sidecar mixer, retaining all the various functions (buss sends, panning, and FB and Echo send, and so on), rather than just using them as preamp + EQ strips. My idea would be to have individual output jacks for the different buss outs, etc. and then to use a seperate line mixer as a group summing mixer. Ultimately I think I'm going to need a schematic for this one. Even if the pinouts can be figured out without the schem, a schematic would be invaluable for upgrades. By todays standards, those 748 opamps are pretty much on par with the 741 in terms of being horrible for audio applications as I understand it (noisy, poor slew rate). Of course back in those days, there wasn't really much else available. It would be good to upgrade these for something like a 5534. I'd also like to experiment with a discrete opamp in the mic gain stage as well as possibly for the main channel output stage. I'm not really all that savvy on opamp theory, but my understanding is that knowing the overall circuit topology forms a big part of deciding what opamp to use in that application and how to optimise its performance (rather than just blindly substituting them). Of course this is where the schematic comes in handy. I reckon I might end up having to trace out a schem if I can; a bugger of a task with all those little daughter board PCBs, plus the fact that the PCBs are pretty much all double sided.

Yeah what you say about that one switch being a master channel on/off swich makes sense. When I first got these strips I actually assumed that the this was what this switch was for, as phantom switches are usually labelled something like “P48” or “Ph” or “+48” rather than just “on/off”. This does kinda throw up a question mark though (for me anyway), about what the “CH” switch (between the pan and solo switches) is for. If the “CH” button cuts the signal to the output, sort of like a mute switch, doesn't this in effect perform the same function as turning the channel on and off?

I have those permanent market crosses on a couple of my strips as well and never really paid it much thought, but what you say makes sense. I've noticed a couple of them have obvious flaws such as disconnected component leads, so I'll have to see if those are the strips that correspond to the crosses (don't have them here with me so can't check at the moment).

From the 748 datasheet I think these opamps can operate at between +/-5 and +/-20Volts, however from what I can see, the lowest Voltage rating of electrolytic cap used on the PCB is 16V, so I reckon you're spot on about them running off +/-15V. I'll try and find the links again to the various 748 datasheets I found and post those here too.

mac

Re: Identify old Nova Sound or JANDS ??? console Channel Strips
« Reply #17 on: July 01, 2009, 01:19:34 AM »
Quote
if the pinouts can be figured out without the schem, a schematic would be invaluable for upgrades. By todays standards, those 748 opamps are pretty much on par with the 741 in terms of being horrible for audio applications as I understand it (noisy, poor slew rate). Of course back in those days, there wasn't really much else available. It would be good to upgrade these for something like a 5534. I'd also like to experiment with a discrete opamp in the mic gain stage as well as possibly for the main channel output stage.

Yes Rob from Pro Harmonics has already suggested this as well. I would like to go down that path too, but I say that on the assumption that I wont like them once I hear them......so maybe I am getting ahead of myself. Lets just get them working first.

Attached is my latest understanding of the pin outs from my investigations on these. Pin 8 has me stumped.

Also, due to the fact that I havent done much on these types of circuits before, I found the Cetec LM 20 schematic had some similarities which was of assistance in figuring out the circuits. Obviously there are lots of differences too, so you may not find this helpful.
Barclaycon: The client said 'That sounds great, what are you using on it?'
The engineer's reply was: '30 years of experience'.

ritz

Re: Identify old Nova Sound or JANDS ??? console Channel Strips
« Reply #18 on: July 01, 2009, 09:53:06 AM »
Wow, great work on the pinouts mac! That's a pretty comprehensive summary of everything considering you used just a multimeter. I'm out of town at the moment so don't have the strips in front of me to check against what I'm saying, but I'll just note some of my thoughts regarding the various pin connections going from your summary...

Initially, I had an idea that maybe pin 8 could be for an effects insert point, but then realised there would have to be at least two pin connections for this (send and return). Also you say it's tied to the red and green wires of the mic tranny, so that would also seem unlikely as an insert point would be after the initial mic gain stage (ie: after that 'first' 748 opamp). I wonder then if pin 8 could be for a 48V phantom power supply... It may be that this board originally had a global phantom power switch in the master section somewhere, whereby switching it on delivered phantom power to all channels simultaneously. From your illustration, those red and green wires are on the primary side of the input transformer, which could support phantom being delivered via pin 8 as the power would have a 'direct' link to the balanced signal lines of the mic input. Also, it might somehow make sense to have all the power supply lines running on consecutive pins (pins 6 and 7 being the +/-15V supply).

Regarding pins 4 and 5, the fact that there's a positive and negative line input connection suggests that the line level input is balanced. I'm not sure, but is this usually the case with line inputs on mixers? I always thought these would generally be unbalanced inputs. Also, the connection from pin 5 to the blue wire on the FB pot and the fader has me baffled. And pin 29, I wonder if this would be a 'direct' channel out.

Also, not being really 'experienced' at all with mixers from an electronics standpoint, I'm stumped on how the solo function is supposed to work with those two pin connections. Do any of the gurus out there know how pressing a solo button on one channel strip is able to make that strip overide the output signal of all the other channel strips? Does it perhaps cause the output connections of all non-solo'd channels to short to ground? And how is something like this achieved via two PCB edge pin connections? Questions, questions, questions...

I think I need to just get a hold of a bipolar power supply, connect it to a channel and then play around with feeding some signal through the input. That would help answer a few questions and also help to unlock how all the panning and buss send connections are routed and how they correlate to one another. This is something else that confuses me: the way buss switch A is linked to left, switch B to right, C to left, and D to right. On most mixers you would press a buss switch, say A, and then panning either left or right  would provide two buss outputs for switch A. So with four buss assign switches and a pan knob you effectively get 8 busses to route to. Here however, certain buss switches are directly associated to either left OR right (again A to L, B to R, etc.). Unless perhaps that A-linked-to-L, B-to-R thing only comes into play when the pan function is switched out of the circuit by the Pan button, and while it is switched in it behaves like a 'normal' mixer as per the above explaination. Again, questions.... and again why I really just need to hook this thing up to some power to figure this stuff out.

Anyway, here's a pic of those A/L, B/R, C/L, D/R buss send switches so people can see what I'm talking about:


ritz

Re: Identify old Nova Sound or JANDS ??? console Channel Strips
« Reply #19 on: July 01, 2009, 10:01:26 AM »
Just some more pics of the item in question:








 

Related Topics

  Subject / Started by Replies Last post
19 Replies
6786 Views
Last post August 05, 2004, 08:36:12 AM
by lanxe
0 Replies
2111 Views
Last post October 28, 2010, 11:04:42 AM
by creal
3 Replies
1616 Views
Last post April 18, 2012, 11:37:25 AM
by JohnRoberts
2 Replies
516 Views
Last post September 01, 2018, 07:06:14 AM
by MagnetoSound