Test IC TL074 CN circuit, CC+ and CC-

Status
Not open for further replies.
C

Coconuttopdrop

Newbie level 3
Joined
Sep 7, 2012
Messages
4
Helped
0
Reputation
0
Reaction score
0
Trophy points
1,281
Activity points
1,312
Hi.

I'm repairing a AMEK mixing board but i dont have an extensor to power the channel's that i'm fixing.
What i'm doing is comparing some readings on a good channel with the bad channel.

The EQ section of the board as 4 TL074CN IC's, and some are busted, but i dont have a way to see wich are ok and wich are busted because i cant power the circuit.

So i need to do some kind of circuit to test the IC's.
The TL074 brochure has a audio amp circuit (fig.25) wich i can try to replicate, but i have some questions.

Using a DC power supply, should i feed 12V to CC+ and hook up the ground to CC- and feed 6V to ground?

Thnks
 

Mixing consoles are usually designed for +/-12 or +/-15 V bipolar supply. Depending on the circuit, you are possibly able to test it with lower voltage.

I can't imagine multiple OPs being damaged without a serious reason. It may happen with in- or output stages, if you e.g. inadvertently connect a speaker XLR cable. Defect power supply with massive overvoltage would be another (very unlikely) possibility and almost mean total loss.

A TL074 datasheet can give you and idea of a basic amplifier circuit, but not of parametric equalizers or differential input and output stages found in a mixer console. I guess, there will be an Amek service manual out there.
 

This is actually a big studio board.
It's has several power rails, the audio ones being +17.5V and -17.5V, 11V for light's...
I cant test the circuit with current, I have no way to feed the rails properly.

The OPs were damaged due to a 50nf cap that busted and was drawing to much current (burned a diode, then the preamp transformer and some ic's on the way)
The thing is that now i have several TL074 that are not working and i need to know what i can do to check which ones are ok and which ones are dead.

There is no service manual for the Amek M1000 on the web
 

Coconuttopdrop said:
Hi.

... as 4 TL074CN IC's, and some are busted, but i dont have a way to see wich are ok and wich are busted because i cant power the circuit.
....
Click to expand...

Why can you not power the circuit ? Maybe using a known power source ?
Busted IC's will remain busted, and good ones good. So what's the concern ?
 


So you say the cause of damage is overvoltage of the +/-17.5V supply rails? In this case I would think about replacing all TL074 powered by the rails.
 

Changed all the IC's and the problem remains, i must have missed something. Thank u all for the help
 

Status
Not open for further replies.

Similar threads

Menu
Log in
Register
Cookies are required to use this site. You must accept them to continue using the site. Learn more…