TAC Scorpion 2 problem

[jensenmann]

More load on the + rail is pretty normal.
Measure the current draw of the rail which has problems and pull single channels. Troublefree channels should show a smaller current drop when pulled, than a faulty channel does. If you know which channel is responsible for the higher load then get an channel extender here: Audio Maintenance Limited Extender Cards

you can connect your channel via extender to the frame but leave it out of the frame to have access to the PCB for further measurements.

Besides all that it sounds strange to me that your tech loaded the PSU with 5A current and everything should have been fine (with not too much excess heat). But then with half of the load through connecting the desk the heat is higher than with fully loaded PSU. That makes no sense to me. Have you been with your tech when he tested the PSU?

Even more so it makes no sense to rework only one of three rails of the PSU when the PSU is pulled apart. That´d have been additional 10 minutes of work and 12USD of parts to have all rails redone. All rails have more or less the same circuit and with age the same faults waiting to occur. Better have a good tech look after your desk: http://www.grssystems.com/ in USofA or http://www.mseaudio.co.uk/ in UK

[vince @ speck]

2.5A pos rail "plus" 1.2A on the neg rail = 3.7A

A linear supply can easily derate 30%-40% at higher temperatures. If a 5A supply is derated 30% that leaves 3.5A.

Take the power supply cover off and keep a small fan blowing on the internal parts... see if it still shuts down.

[jensenmann]

I have the same desk with the same configuration but with heaps of opamp upgrades and additional stuff installed. This literally doubled the power consumption. My stock PSU works absolutely troublefree even with the increased load.
Vince is right about the fan, though. I´ve added a fan later to keep temperature low enough since I´ve mounted the PSU in a rack with only small airflow inside.

[customjay]

Thanks for your replies...

I have already tried removing the cover but I always get the same problem of the power cutting.
My power supply never overheated like that before with its cover on and installed in my rack.
I forgot to mention that the problem began with reductions in volume of sound and the "LEDs" which lowered(dimmed) in luminosity, moreover since I have seen a bus meter which does not work any more.

[Matt Syson]

Hi
The power supply needs repairing properly and testing under load. There were 2 versions of the AMEK/TAC supply with one having a fan fitted and a larger mains transformer. You can simply add a fan if it doesn't have one, 80mm Square with voltage to suit your mains. The originals had 110 Volt fans so it could work on 120/240 but if you are in a 220-240 country, use one to suit your mains so it won't waste extra heat in the transformer.
Disconnect anything on the desk which is faulty and get it fixed when you can.
These supplies can handle 5 amps on both rails simultaneously so that should not be any issue. They can give rather more but would tend to get a bit warm.
As with all linear power supplies there are 'boundaries' that they will work in and there is a 'product' of time and temperature that is one of the definitions of their 'capability'.
A supply which runs at 30 Centigrade will last a long time, unlike one that runs at 100 Centigrade (measuring on the regulator / capacitors). These supplies would give around 11 Amps on each rail but not simultaneously, or for indefinite use. The limitation is essentially the heatsink and ability to get rid of heat.
Matt S

[customjay]

Hi ,

I removed all the tracks/channels from the desk yesterday, it has allowed to clean them up a bit,
I am going reinstall them later today, after a visual check .
Question: Can install each track one by one??
With voltage or not , do i need to turn off for each step or not
to determine which track/channel is causing the problem when i plug them back in?
Here is my Psu .....

[jensenmann]

Let your desk run without any channels fitted. If the PSU still overheats then the fault may be in the meterbridge.

[customjay]

Hi, thanks for your help

i plugg the pSU with 16 mono channels and the master channel too
it look likes ok ...just wait ..
but i still got problems since a long time on the master channels...
I often loses the right signal, no sound , no right meterbridge , but.. works on the monitor with mono switch on the master channel or PFL on S1101 too ! i control the 2 faders L/R , they ve got the same resistance
so i change the wiring Left to right on the stereo channel board , and still the same ,just got the left meterbridge... control by right fader of course
so i unplugg the headphone cable too if ... why not but doesn t change !

in these case i had to push the channel towards the PCB and sometimes appears the sound and signal ???
i suppose it s come from the stereo channel board ?? Since I have unplugg everything channels yesterday it does not work any more...rrr

[jensenmann]

It sounds as if your desk needs a serious service.
Your master may have a problem at the ribbon wires/connectors or insert jacks. But remote-diagnosis is not very precise. Someone should have a closer look at it. What´s your location in France? You´re aware of the analog console forum? Analog Recording Console Forum • View forum - AMEK & TAC Recording Consoles

[customjay]

Hi ,

thanks again Jensenmann for your help

Of yes I know that I have to restore the system, but it worked perfectly since 5 years, it comes from a thêater , the last check was in UK in 1992 !
i'm living near Le Mans and it s really strong to find a real technician fascinated by the vintage gear and music .... you know what i mean !

well yesterday no problems with the PSU , 40 ° C working (a long long time with the cover) with 20 mono channels , 6 bus channel , and the master channel (Which always has the problem on the right /side ) at the moment .
i m searching for the solution . I know that sometimes the inserts stereo channel put the mess , but won t work yesterday !

I'd probably find the solution with the bus meterbridge n°7 which did not work any more. So i plugg unplugg , change the bus channel, change the fader , compare and so .... and all the bus meterbridge works PERFECTLY yeahhhhh !! so it comes from the bus channel n° 7 for sure
i disconnect the bus channel n° 7 right now ! and that s ok at the moment .

So did the problems with the bus channel n° 7 could destroy and damage my PSU and put the mess ?? does it means i find the solution ? i hope so
CustomJay

[jensenmann]

Shipping single channels is not so expensive. You could send the defective strip to Matt Syson who is an ex-Amek employee and knows these desk better than most other techs. He surely can help you fixing it.
If you need ribbon wires then let me know. I have a bunch left over.

[customjay]

Originally Posted by jensenmann

Shipping single channels is not so expensive. You could send the defective strip to Matt Syson who is an ex-Amek employee and knows these desk better than most other techs. He surely can help you fixing it.
If you need ribbon wires then let me know. I have a bunch left over.

Hi ,
somes news from the TAC , the last check with all the channels ( except bus n° 7 and the master ) is ok !! no more overheats from the PSU .
i put a fan inside , and it s amazing the temp is now 25° c
instead of 45° c after many hours !! i m going to send to Matt Syson the 2 tracks . Thanks for ribbon wires if i needed .

special thanks to Jensenmann and Matt Syson

[Matt Syson]

Hi
I see your supply has no fan installed. This is not a problem as such, but if you can tolerate some fan noise in your setup, fitting one will help it stay cooler and last longer. If you use a 230 Volt fan you can select different voltages on the mains transformer and get it to 'run slow' which is considerably quieter. I would suggest something like 180 Volts if can work it out. I can't remember all the tapping permutations available but it is worth CAREFULL experimentation.
Matt S

[brentworth]

I'm looking for a TAC PS. Can't find one. I bought one when I got the board but judging by the pictures above, the PS that I have is under powered. How many watts do I need to power a 32 channel Scorpion? The unit I have consists of: HDD-5-A, HB12-1.7-A, HB48-5-A.