Rare Trident Model L29 Limiters - Caught in Nashville Flood

Hi All,

I have a pair of Trident L29 Limiters that were submersed in water during the floods here in Nashville. I am trying to restore the relics so they can be put back into use. After a thorough cleaning, they were put back together and not working right. I am looking for any schematics or documentation. There are two cards that make up this unit, model numbers 9054A and 9054B. I have talked to several people trying to get some info. on these but to no avail. I don't think many of these units were made at all and the people at Trident didn't even know where they came from. Any help or suggestions?

Here is a pic of the faceplate.

what is not working right about them?

They pass audio but are not compressing/limiting the audio at all. They are acting more like a preamp and gain stage. The meter is not show input and only show gain reduction when I slam the input with about 5VAC sign wave. I'm not to savvy with older units like this, especially with no schems. 

Are you sure they are TOTALLY dry? Maybe the pots are damaged? I have dried out radio receivers and servos etc. But takes a LONG time. And they will work properly eventually. Chokes and coils etc.  can hold water almost forever. Water may have traveled down the shaft of the pot. If the pots are kinda sealed on the back it may still be in there.

Look at any component that could still be holding water. Water won't kill it unless there is still some there. When it dries out it should work. Was it powered on when it got wet? That could be a problem...

Maybe someone here can post a schematic. Hope ya get it all working.

John

did they work pre flood?

Both units were actually given an ultrasonic bath, (excluding the I/O tranny's) and sat in a De-humidified room for several weeks in attempt to make sure they were bone dry. Pots were properly cleaned and lubed, they seem to be operating properly with no dead spots or noise surprisingly. As far as I know they were not turned on while being under water. Meters had to be replaced. Schems would be great.

They were in working condition before the flood. Power supply had to be srapped but I managed to find the same supply on Ebay for $40.

Hopefully someone here can help you. I made a couple calls to other studios and none of them have heard about that limiter... They must be VERY rare. I even called the old guys. They said it must be from the 70's.

John

I have asked several people as well. The only information I got from anyone was a guy in Italy that use to work at a studio that had these modules in every channel of an old Trident console. He also said that as far as he knew that was the only model of that type that they produced. The people at Trident as we know today have no record of them ever being made. There has to be a paper trail somewhere, just incredibly difficult to find.

From my experience switches are like cats, they dont like ultrasonic bath. Mabye the in/out switch just turns of the sidechain??
Some nice close up shots of the inside would be nice. Is it a fet or opto or diode compressor?
Old optos have a ligthbulb...could be dead.

Well I'm just an amateur experimenter. But there are lots of heavy hitters here that could possible fix them for you by tracing the circuit.

The weird thing is they actually look familiar to me.

John

Are you sure they're not a derivative of the Trident stereo limiter ?  Do they contain op amps or are they fully discreet ?  Maybe you could post some internal pics ?

thefastvinny said:

They pass audio but are not compressing/limiting the audio at all. They are acting more like a preamp and gain stage. The meter is not show input and only show gain reduction when I slam the input with about 5VAC sign wave. I'm not to savvy with older units like this, especially with no schems. 

Click to expand...

An open sidechain loop (i.e. send/return) would keep them from compressing. Both having the same symptom would point me in that direction. Are those the looms/connectors they were wired to originally when working?

lets see some guts of this thing... are they fet? 

All wiring is original. I would assume that there is a Sidechain Input on them however, it does not look like it has ever been wired up or used since they were mounted in this rack, just Input and Output. It is FET with a few MC1741 Op Amps. I will get the guts on here later on today.

If they are still wet then putting them in a vacuum chamber will dry them out faster.

Yes, they was made by Trident in the old Triad A and B range time.

They are FET based.

It was made in two versions, CB-9054 with 3 knobs and 4 switches, and CB-9064 ? with 4 knobs and 4 switches.
Later they also made the 19" rack version CB-9146, also same circuit as Fleximix compressor module.

Maybe the UK company Audio Design & Recording was involved in this design ?

I have tried for years to get the schematics for these oldest compressors, it has never succeeded.

Have also talked with staff from the old Trident factory, but no one remembers anything or have any saved information.
If any of you find information, so please let me know.

Some small tech tips,

These compressor modules were designed to fit in the Triad B-range consoles,  and this console modules would have a supply voltage of 45 volts . (they have a internal 24 volts regulator, so the input voltage must be a lot higher than 24 v)
But check this first, so the compressors not are modified.

Because of the age, it's probably many dried electrolytic and tantals, a good idea is to replase them all, because many of them have important functions in side-chain and rectifier.

--Bo

Here is a shot of the Top PCB(9054A).

So these comps are coming back to life. All I need is a couple output transistors. Does anyone know where to find RCA 40361 and 40562 transistors? Very obsolete and hard to find. NTE had a cross reference for them but I can't even find a pin out for the originals. I would rather keep the original spec parts if at all possible.

I find nte allthough more pricey  to be pin for pin like the original replacement usually