Help Me Diagnose my Console problem, please.

[firby]

Hello esteemed slutz.

I am having a problem with my console. It is a Trident 24. I am getting a really weak left channel with static off of the master L and R buss. There is program material at normal volume on the right channel but a big static buzz on the right channel.

Here is what I have done to try to diagnose the problem further.

1. Redid the power to the board so that the board and all of the studio come off of one outlet that checks clean with a yellow yellow red plug in tool.

2. I changed out the amp driving the monitors and the problem still remains.

If I pan a signal left it all but dissapears and gets static ee. If I pan the signal right its ok but a buzz probably a little under 1k that is a little bit inconsistent sometimes.

The things that have changed are the ac is on now a lot and I just brought home a new keyboard that does not have a grounded plug.

I think however that it is something on the master buss card maybe a chip going out or something ? I don't have lots of money at this time so I am looking for a way to diagnose and fix it or at least diagnose the problem and then take the card to somebody. If it is just a chip I can do it myself as they are socketed.

Please help.

Regards.

[JohnRoberts]

Basic troubleshooting would be to check where the signal gets corrupted.

Are aux sends clean? Is signal clean at insert points?

Sounds like problem is inside the console, perhaps internal connections.

JR

[Matt Syson]

Hi
Or patch points particularly if they are outside the desk.
If you have patch points available, use a pair of cords to swap left / right and pre / post main fader to isolate where it is working and where it is not.
Matt S

[firby]

The Auxes are clean, and I seem to have it down to the card, I think. Is there any way to decisively determine whether it is in the master buss card or not ? I unfortunately don't have another masterbuss card to swap it with.

[firby]

Originally Posted by Matt Syson

Hi
Or patch points particularly if they are outside the desk.
If you have patch points available, use a pair of cords to swap left / right and pre / post main fader to isolate where it is working and where it is not.
Matt S

I think I can do this. There is an insert and returns on the master buss, so I will see where the audio still sounds good.

I can also check the direct outs on the channels to make sure that it is not the channels but I think they are clean.

[soundbarnfool]

Is it at all intermittent? Does it change when you press on the master section, etc?
If so, it's a connection. If not, somethin' blowed up. Was it recapped recently?

Inglewood SoundBarn

[firby]

Well. It has been building, getting worse for a week or two. Now it is not intermittent. ... Here's hoping. It sounds like maybe I could reseat some cards. I did have one adventure where reseating the card made a voodoo like change in a channel card.

That mixer is old enough and rare enough that I don't just go tearing into it with abandon, but obviously something needs fixed now.

Before (months ago) it would sizzle intermittently on startup. Then about 5-20 minutes later it would be quiet and we would go on with our work.

I would have a guy out to look/listen to it immediately if I weren't cash strapped at the moment.

The board was modified in the 80's when it was new, there are some tlo71s or whatever they are that are nec chips and not every channel stip has the same chips, esp in the eq sections. There was talk that it had been recapped in at least parts, but I don't really know whether it has been or not. I do think that the power supply is not original and that the auxes have been modified to have more gain.

Again I think that was all back in the day, I am the third owner and I believe that the second owner just kept it going and in good shape and was not one to augment it.

I have a paper that has a bunch of chip numbers on it but I have not ever really deciphered them. Also have something about the PS.

[ktf]

All the above is great. Sounds like it may be time for a schematic and a scope or simple signal tracer and a test tone. And of course some means of access while the console is on (extenders?) You should be able to determine what section the problem is in with the above advice. If you don't have the tools a visual inspection will often yield results. Look for bulging or leaking caps / bad mod wiring / cracked solder joints etc.

[JohnRoberts]

If you get similar pan problems from multiple input strips then the problem is likely isolated to the master section or a common bus wiring issue.

JR

[firby]

I think that I have it isolated to the master section. I have noticed that even with the master gain all of the way down there is some crackle. There is a bit of static in the auxes as well but it is nothing compared to the static buzz on the right side of the master.

Yesterday I had to do some work so I mixed auxes, but that will get old REAL quick. So I have to fix this.

One question. On the master card are a bunch of socketed ICs, its likely tl071s and NEC 55xx style chips, I think. Does this type of problem sound like a chip failure in one side of the master module ?

If so, I feel competent about replacing the chips in the master. The master module might even be a good place to mod via cleaner/better chips if it needed touched anyway.


Is there a method to taking a chip out and seeing if it is dead or not ? I can scrape up a multimeter(fluke), but I don't know about a scope.

I'll take the thing out and take pictures tonight.

Regards.

[JohnRoberts]

Outright IC failures are pretty rare... more likely solder connections, tired caps.

Typically the bad parts will not glow or change colors so troubleshooting requires test equipment and some skilz...

JR

edit- It might be worth re-seating the opamps in the sockets and wiggling connections to look for intermittent.

[ktf]

[QUOTE=firby;4311357]Well. It has been building, getting worse for a week or two.

That's not how chips fail.

[Bluzzi]

If you have schematic (or not) and can determine which chips if any are left buss and which are right buss than just flip them to see if problem follows. It could be leaking capacitors as well. Try the chips first. you never know until you try. Use common sense, sometimes it does result in a solution.

Also is your master section removable? Then also try some contact cleaner on the connecting parts. Check the PCB for cracks or broken traces. If you have an extender card, tap and/or budge parts while listening for changes in noise.

These are some of the things you can do to at least get to know your board better and if you need a tech down the line you can at least let them know what you have tried.

Jim

[SAnthony]

I would probably "shotgun" all of the caps in the Main L/R Output IC section. I don't have a schematic in front of me, but I'd say Remove all polarized electrolytic Caps in this section of the circuit and replace them with new caps... This probably only involves 8 Caps or less.....
Hope this helps...
Shawn

[John Eppstein]

Originally Posted by firby

I think that I have it isolated to the master section. I have noticed that even with the master gain all of the way down there is some crackle. There is a bit of static in the auxes as well but it is nothing compared to the static buzz on the right side of the master.

Yesterday I had to do some work so I mixed auxes, but that will get old REAL quick. So I have to fix this.

One question. On the master card are a bunch of socketed ICs, its likely tl071s and NEC 55xx style chips, I think. Does this type of problem sound like a chip failure in one side of the master module ?

If so, I feel competent about replacing the chips in the master. The master module might even be a good place to mod via cleaner/better chips if it needed touched anyway.


Is there a method to taking a chip out and seeing if it is dead or not ? I can scrape up a multimeter(fluke), but I don't know about a scope.

I'll take the thing out and take pictures tonight.

Regards.

Try simply reseating the chips. Sometimes thermal cycling will cause chips to work loose from their sockets, resulting in a bad connection.