Patchbays - Wiring Harnesses and Molex issues

I started working on the patchbays. I found 2 gently used 96 point TT bays in Nashville. I cleaned them up and de-soldered the original cable ends. I don't have a heat gun but I do have heat shrink in my "care-package"!... go figure. I will use shrink only when necessary...

I have the first mic snake wired up on Mogami 8 pair. The Molex pins on the mic inputs to the console are not removable. (14$ later for a molex tool... unusable) so I have to buy 3 hole 0.093 Molex conectors.
I will rewire them with some single Mogami I have. Just enough for 16 inputs to the bays.

My eyesight is so bad now that I have to use my readers to see the solder lugs.

I built a holding jig to hold the bay at the right angle.

I got Susan to assist me in clipping out the old mogami!

 

16 Inputs - Ready!

I have reworked all 16 IO modules. It has taken about a month and a half. about 1.5 hours each day.

Tangent 3216. circa 1979 Recording Console that I am rebuilding.
All modules have been reworked and I am testing audio through the system.
There are a few problems remaining in the metering; a VU and LED meter problem.
Ready to start the patchbay!

I powered it all up and it sounds great!. I tested all the mic pre's and tape inputs and outs.
Then I did tests of the submaster busses. I have one VU meter acting up on #10, I will torubleshoot it.
A 4016B Comparator a TL084 opamp and 3- LM336's for the LED drivers. the Peak Reference transistor pair is fine... and another VU modeul works perfectly when swapped out...


The Master Module is ready.

I put in the TB Oscillator module and it is working to all busses except 16. I think it is the finger module.

TB Osc Module - Peak Ref adjust (+15V)

TB Osc Module - Main board - ICL8038 VCO . I have a mod idea!

I read the datasheet on the ICL8038 VCO IC. The Tangent 3216 provides a sine wave output to the MIX, CUE, or BUSS. I read that the IC also supports Triangle and Square waves on pins 3 and 9 respectively. I think I will pull those out to the patchbay for a handy tone reference jack! Just add a resistor to ground. I will try 1K, 10K and 100K. Cool...

I also had time this week to build some shelves that I promised Susan long ago... came out pretty good! lots more room for storage now... ~30$ of wood and 3 hours...

Metering - LED and VU

Metering. The console uses LED meter for each channel. It can be globally switched between Peak and VU modes.

IO Modules - 9 of 16 Completed!

I have

Designing the studio...

I have been working on the console off and on after work in my spare time.
I bought it Oct 1, 2011.It is now late Nov and I am on vacation this week. I am setting up this blog...

I have been using Google Sketchup to design things. I really like it. It is very easy to use once I got used to it.
I even use it for work to design and plan projects.

And its is FREE.

I am on a zero budget!

Here are some of my sketchup ideas for the studio... Someday...

I even created a Tangent 3216 model. It needs some tweaking still...

I drew this from memory. It was pretty close to the real thing.

I wish I had the Studer. Google had a good model so I grabbed it.
I will find a good multitrack solution someday...

Troubleshooting 101 - Logic - In Circuit...

The circuit boards do not have a silk screened layout on them. So it is hunt-n-peck to find what you need.
The schematics I have with the console are like the dead sea scrolls... deciphering them is taking quite some time. I scanned the really illegible ones and blew them up. Since this is my console I marked up the circuit boards with my notes, etc...

Submaster amps. 4011 nand gate. solo fet's.

Created this to help me find my way around the IO Module.

My friend from work is an electronics person. He loaned me his ESR meter. I checked all the caps and most were fine. I replaced any bad ones that were off the scale. I did not know that much about ESR and I am glad now that I do. It even works in circuit. His was a kit he got at: ESR Kit

Troubleshooting 101 - Master Logic.

The console uses an X and Y logic buss to set up the signal path. The modes are INPUT, TAPE, and MIX.

Using the switching logic you can place the Mic Pre or the Tape In to the Chamnel (EQ, Phase, Cues, etc) or the Left Right Monitor Mix.

The Input Output Modules (IO) use a CD4011 quad CMOS Nand gate to define the logic states from the X&Y busses.

The output of the logic controls JFETS that are placed to either allow or block the signal path from the mic pre or tape inputs to the channels. When the JFET has a -15VDC on the gate it turns on the FET and either allows signal or shunts it to ground.

What really confuses me is that the circuit is using negative logic. In other words VSS is not +15vdc as in normal cases. VDD is -15V. So a "true" or "1" state is actually 0vdc ground. a "false" or "0" is -15vdc.

Here is a more in depth example below. The Tape Input flows thru the N-channle FET Q13 if S2C is at -15 logic state. And in this state Q11 shunts the input to pin 2 + input of the LM351 opamp. effectively to ground... "muting" that input to the Master LR 2 mix...

Now on to more troubleshooting....

Disassemble the console.

I pulled out all the modules and did a basic visual check. Nothing burned up and everything looks good.
The factory patchbay is missing on this console but the wiring harness is still there and it has the original Molex pins at both ends. I need to purchase some spare molex connectors 0.093 3X3 and a few 4X4 and an extraction tool.

I ohmed out the power supply rails and nothing shorted in the backplane.
The back plane looks Ok in general. There were some minor repairs done on it in the past.
It needed a good high pressure condensed air blow out.

It powered up and did not blow a fuse.

However the switching logic is not working. The X buss is in that "floating" state near 1-2v instead of a solid 0v or -15v

Troubleshooting Time!

Power Supply. It starts here...

With no idea of the electronic and functional state of the console I decided to treat it as if everything imaginable could be broken... maybe pessimistic but then I can be pleasantly surprised when I don't have to fix something.

First place to start is the power supply...
The Tangent used a linear supply. +15 VDC 4A, -15 VDC 4A, Ground, and +48 VDC 1A for Phantom powering of condenser mics. Each leg is fused and the mains are fused.

Pop the Top.

The supply needed some work. I was not about to power it up without checking the entire thing out thoroughly.
At my age I don't need to fight a small fire. LOL.

This will take some time to check out... It is missing the +48VDC leg in it's entirety...

The transformer schematics are not quite accurate as to what I am seeing.
A separate Full Wave bridge rectifier for each leg; +15 -15 and 48.
A hefty filter cap for each. 4700uF for each +/- 15 VDC and a 6700 uF for the 48V.
Then it uses a 7815 TO-3 regulator...(and matching 7915 for neg 15) mounted on heat sinks on the back.
Then fused and out to the console on a multi-conductor cable.

The +48 is achieved via a 7824 TO-3 that is referenced via a 24V zener at the input.
Here is that zener diagram:

OK. Here we are a few days later. Confident to power up now.

Update: 11-26-11...

I replaced the 6700uF 75VDC filter cap. The ripple is GONE. No hum in the phantom powered mics. I used Danny's ESR meter and the old one was off the scale. The new one was a perfect 0.30...

I really like ESR measurement.

Discovery and Housekeeping... Test equipment and parts

I set up a workbench and pulled out my old oscilloscopes and electronic gear I used back in my greener days when I worked as a bench tech. My multimeter was totally trashed and the LCD display would not work. This project has to be on a zero budget. So I will reuse everything I can salvage from my old boxes of parts and connectors. I just need a meter that has an audible diode test and a large number display. I bought one at Altex for less than 20$. I will repurpose some mogami cable and harnesses that came in a donated care package from another studio install many years ago.

Set up the workbench and find out what old gear I had stored in plastic boxes in the shed.

Tangent 3216. Project start and background...

I am rebuilding a circa 1979 Tangent 3216 analog recording console. I have installed three of these consoles in the 80's. This one is a 16 input model with a producers desk and patchbay. It is also a bit unique in that it has VU's in the master section as opposed to the LED meters.


The Tangent 3216 was one of (if not the first) to use a transformerless design.
It is an inline style console. There is not a separate tape return module group.
I personally prefer this style of console.


I will be reworking this console from the ground up and then add some modifications.


I will post as the project goes along.

1979  Tangent 3216 16 input 16 buss inline console with producers desk.

Picked up the console. Luckily a 16 input will fit in the truck.

Here are some old pictures from the 80's at Walk On Water studio in New Braunfels.

Walk On Water studio 1983.
I completely remodeled the control room and rewired the entire studio.
This was a 16 input 3216 and I built an external patchbay and effects rack.

Walk On Water Studio 1984. View from studio into the control room.

3216 in the control room. 1984 Walk On Water
Lexicon Reverb. The MS16 tape machine was in a soffit in front of the control room.