TAC Matchless stereo buss problem

Graham Langley founded Amek in 1973 with Nick Franks. Since then, AMEK and TAC recording consoles have been the choice of demanding audio professionals for over 25 years.

Moderator: Matt Syson

TAC Matchless stereo buss problem

Postby Behemoth » Thu Aug 01, 2019 5:24 pm

Hello everyone,

This is my first post here, I've been lurking around reading everything about TAC and Amek desks on this forum and have come across some very interesting stuff about analog desks. I'm new to the world of servicing and fixing (old) analog desks but I'm very interested and eager to learn!

Problem #1:
Last year I bought a TAC Matchless (26ch one) which was in pretty ok condition, not factory-new but definitely not neglected. I've been playing around with it for a good while and as with any old desk the potmeters started to crackle, what's even worse is that my stereo monitoring output was crackling hard and started to lose the right audio signal. Okay no problem I thought, just ordered some Deoxit D5 and F5 and after some time of postponing I started the great desk cleanup.

I was pretty satisfied with the results, most potmeters just didn't crackle anymore at all or stopped crackling after another good knob wiggle. However there was a bigger problem lurking...
All of a sudden my stereo buss had no signal on the right path whatsoever! What's even more strange is that if I simply sent audio signals to the monitor path and assign the monitor path to the main stereo outputs I do get outputs on both left and right. So it has to be a problem on the right channel of the stereo buss output.

I've been bypassing the problem by simply sending my interface monitor output to an external input to the desk but obviously I'd like to fix the problem 'cause you know... Would be nice to be able to use the desk for summing (via the mic/line large fader path).
Seeing as the problem is the same for every single channel it has to be in the master module. I've got the module out and inspected it and saw some of the pins of the edge module connector (64 pins, on the back) were crooked. So i took a couple of tweezers and attempted to make them straight again. This worked for all of them except one. That one was so crooked it broke off immediatly after touching it for even a split second.

After looking at the service manual I saw the broken pin labelled as: "line -⌀ ". I don't know what that means though, there is another pin with the right stereo path which is fine. Can anyone help me out?


Problem #2:
When I use an insert on the desk via the patch bay it gives a weird pulsating low frequency noise blended with some of the original channel (very distorted). This doesn't happen if I return the insert to a different channel and also doesn't happen If I hard-wire the insert directly into an external patch/directly into the compressor with a Y-split cable (bypassing the patch-bay). I've never wired a patchbay myself so I don't know what to look for.



Thanks in advance for your time and knowledge guys ;) !


TL;DR: Right stereo buss channel doesn't work (main stereo outputs/monitor stereo buss works just fine).

TL;DR 2: Patch-bay insert/return doesn't work as it should
Behemoth
Analog Owner
 
Posts: 4
Joined: Wed Jul 17, 2019 4:56 pm

Re: TAC Matchless stereo buss problem

Postby Behemoth » Thu Aug 01, 2019 5:25 pm

Also if somebody knows where I can find original TAC (Matchless) knobs that would be great, I've been searching the internet to no avail :/
Behemoth
Analog Owner
 
Posts: 4
Joined: Wed Jul 17, 2019 4:56 pm

Re: TAC Matchless stereo buss problem

Postby jensenmann » Tue Aug 13, 2019 9:17 am

There are several spots that can cause problem #1:
The master outs have their own inserts at the rear of the channel. It´s possible that there´s a contact problem in the insert jack. To check that out use a TRS jack and solder tip to ring. If you insert this it will open the eventually dirty switching contacts which often have contact problems with age. But the short between tip and ring will return the signal into the desk.
There are some ribbon wires connecting the masters which use Molex selfcutting contacts. The copper of the ribbon wires gets exposed to oxygene in these contacts and may deteriorate over time. It might be a good idea to recut the ribbon wires at another spot or completely renew the entire cable assembly.
Some other things are possible of course, but that´d need some on location inspection.
I hope that helps.

The knobs are unobtainium. Maybe just buy a channelstrip on ebay and part it out.
Jens
jensenmann
Yacht Rocker
 
Posts: 275
Joined: Wed Jan 31, 2007 6:08 am
Location: Karlsruhe, Germany

Re: TAC Matchless stereo buss problem

Postby Behemoth » Wed Aug 14, 2019 5:19 am

Thanks for the response jensenmann,

I'll try out the insert jack tip-ring short to see if that solves it, if not I'm trying the ribbon connection.
As for the knobs, I found some pretty close lookalikes on Sifam's site.

Lastly, do you have any idea what the "line -∅" means in the edge module connector?
Behemoth
Analog Owner
 
Posts: 4
Joined: Wed Jul 17, 2019 4:56 pm

Re: TAC Matchless stereo buss problem

Postby jensenmann » Wed Aug 14, 2019 10:20 am

If you mean pin A30 on the 64- Pin DIN connector then it should be unused on the master.
Jens
jensenmann
Yacht Rocker
 
Posts: 275
Joined: Wed Jan 31, 2007 6:08 am
Location: Karlsruhe, Germany

Re: TAC Matchless stereo buss problem

Postby Behemoth » Wed Aug 14, 2019 9:59 pm

jensenmann wrote:If you mean pin A30 on the 64- Pin DIN connector then it should be unused on the master.


Yeah that's the one, good to know thanks :)
Behemoth
Analog Owner
 
Posts: 4
Joined: Wed Jul 17, 2019 4:56 pm


Return to AMEK & TAC Recording Consoles

Who is online

Users browsing this forum: No registered users and 8 guests

 
Mr Patchbay sells patchbays, tt/bantam cables and more