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Trident 65 Module Signal Dies when EQ engaged
Old 9th February 2019
  #1
Gear Maniac
Trident 65 Module Signal Dies when EQ engaged

My Channel passes audio via line no problem. When I engage the EQ button the audio does not pass. The EQ engage light works though.

I know this second part will sound foolish: The channel and it's EQ were working fine. The console was off, and I pulled the module out to deotix the knobs. I then turned on the console to check some other knobs for noise. I put the module back in and accidently made connection with a piece of metal from the sister channel which made the module spark a little bit. That's when the EQ went.

I'm wondering if someone could help me with information on how to troubleshoot where the problem area is. I have a multimeter and LCR Pro 1 plus for tools. I'm just not sure which settings I should be on, and how to go about tracing from point A to point Z. But I have a thought. Am I right to this to hold onto Point A and B with the audio indicator going on the Multimeter, then go from A to C, then A to D (etc.) until I hear no signal?

I'll include a picture of the Diagram as well as the module. Any help you have would be so appreciated.

Thank you so much, community! I'm determined to learn how to get this fixed
Attached Thumbnails
Trident 65 Module Signal Dies when EQ engaged-screen-shot-2019-02-08-6.39.26-pm.jpg   Trident 65 Module Signal Dies when EQ engaged-img_2225.jpg   Trident 65 Module Signal Dies when EQ engaged-img_2226.jpg   Trident 65 Module Signal Dies when EQ engaged-img_2227.jpg  
Old 9th February 2019
  #2
Lives for gear
 
Brian M. Boykin's Avatar
You’ve already narrowed it down to the EQ section. I’m having a hard time reading the fine print from the pic you posted. Find the EQ input switch on the schematics and then test everything after that. You can run a 1khz tone into the line input and trace it with a multimeter. Sometimes if an opamp is actively shifting I’ve found it by placing my finger on them one at a time and the shooting one will burn your finger. Not as accurate as tracing. If you have a scope you run a 1k hz frequency and trace it that way also. But if all other functions are working except when the EQ is inserted I’d start there.

Brian
Old 9th February 2019
  #3
Gear Maniac
Thanks, Brian. I’m really new with schematics, and don’t completely understand how to trace them just yet. Could you recommend a video on YouTube to watch as a tutorial or something like that? Thank you very much for responding!!
Old 9th February 2019
  #4
Lives for gear
 
Brian M. Boykin's Avatar
Set your multimeter to the AC setting. Audio is alternating current. Ground the black probe. With the module plugged into the console and a tone being sent to the line input start at pin 1 or 7 (which ever corresponds to the line input) of the first opamp and then follow the signal to the next component on the schematics. Eventually you’ll get to the component that’s not passing audio. You may have to remove serveral modules on each side of the broken one to make room to work unless you have an extender cable. And don’t worry. It’s fixable. And the opamps are in sockets so they’re plug and play if it’s an opamp. I don’t see any transistors after the mic pre so I’m thinking it’s an opamp in the EQ section.

Brian
Old 9th February 2019
  #5
Lives for gear
 
Brian M. Boykin's Avatar
I google “trace and audio signal” and got several hits for tutorials and YouTube videos. This could be the beginning of your inner nerd.

Brian
Old 9th February 2019
  #6
There are about 5 TL071 opamps in that EQ circuit, mounted in sockets. Swap them. Also clean the EQ switch.
Old 10th February 2019
  #7
Gear Maniac
Very useful information, Brian. Thank you very much. I will give it a shot and report back
Old 10th February 2019
  #8
Gear Maniac
Thank you, Jim. I could grab some from another channel, drop them in, and see if it does the trick. If so, place an order for some new TL071’s.

Quick thought - Do you think it would be worth buying some higher quality opamps?
Old 10th February 2019
  #9
Trident 65's require some feedback caps and power supply bypasses installed. Other stuff is needed like a series resistor on the direct outs. Then good opamps will work well and will drive 600 ohm outboard gear.
Old 4 weeks ago
  #10
Gear Maniac
That's good information. Thanks, Jim.

I did try swapping out the TL091's with a working channel with no luck. I'll go ahead and try tracing the signal next. I guess keep it in the console with it on and try not to touch anything with the bare hands?!




Quote:
Originally Posted by Jim Williams View Post
Trident 65's require some feedback caps and power supply bypasses installed. Other stuff is needed like a series resistor on the direct outs. Then good opamps will work well and will drive 600 ohm outboard gear.
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