Crest Century TC Channel Repair

[Brian Roth]

Can you post any pix?

Bri

 

[Brian Roth]

Oh.....and the lytics could be possible suspects. Film caps should be OK.

Bri

 

[jensenmann]

Here´s my online schematic collection. Maybe you can find something that helps: Schematics and Manuals

 

[la80vette]

Here’s some pics

 

[la80vette]

Jensenmann,
Thanks for the schematics.

 

[scott2000]

Nice enough looking boards. Can imagine lytics or maybe goofy connectors being a first line of business. Perfect place to start getting your feet wet. Just be patient when desoldering and removing caps to avoid pulling off any pads to eliminate having to add any jumpers....

 

[Brian Roth]

It sure looks like that desk is NOT filled with electrolytic coupling caps...a common failure source on many desks. Unless I missed something, the only lytics I spotted are most likely power supply rail bypass parts.

In turn, channel failures would be most likely due to some sort of crappy connector/soldering and failed opamps.

Bri

 

[Brian Roth]

One other "Troubleshooting 101" question. Have you tried moving the "bad" modules into an otherwise-known-working slot in the desk? And, move that good module into the corresponding "bad" slot position. Does the failure move with the module(s)?

That testing would probably eliminate any frame issues (internal wire harness, funky insert point jacks) and point to the module itself having a fault.

I need to see if I can find a block diagram for that desk in order to narrow down troubleshooting.

Bri

PS....have you exercised the various switches and pots on the bad modules? That falls into the "bad connection" possibilities.

 

[la80vette]

I've swapped them all over the place. I was trying to get 20 working channels in order. But yes, the problem moves with the module. I can get the input signal and clip to light up on all channels but one but no useable output on the bad channels.

 

[Brian Roth]

I'm lazy....any chance you have the signal flow chart through the desk??

Bri

 

[Brian Roth]

Also....BTW...Crest desks were very well designed and built, so worth some time to fiddle with.....not made with Chineseum. I WILL not get into any conversations about if they had any "magic sonic mojo" or..."Crest desks sound like crap". I just thought they were well engineered, and at "worst" were hi-fi/neutral. Built like a brick ....house <g>

 

[la80vette]

All I have is the block diagram. I don’t know if that’s the same thing as signal flow.

 

[la80vette]

Yesterday I ordered 10 electrolytic caps from Mouser to replace on one channel strip. If it's successfull, I suppose I could continue.
Regarding The Crest moniker, yes, this and the Midas were the ones to have back in the eighties and nineties. They were both workhorses, highly dependable, good construction and easily serviceable with good clean sound.

 

[Riley Casey]

Back when we had Crest consoles we discovered that after a few years of the portable life that it was beneficial to unmate and remate all of the ribbon cable connectors several times on the entire console at least once a year. Not likely to be an issue with channel strips that have no output in multiple positions but another thing to check is the insert point jacks. Dirty normals could give the results you describe.

 

[la80vette]

Back when we had Crest consoles we discovered that after a few years of the portable life that it was beneficial to unmate and remate all of the ribbon cable connectors several times on the entire console at least once a year. Not likely to be an issue with channel strips that have no output in multiple positions but another thing to check is the insert point jacks. Dirty normals could give the results you describe.

I'll be sure to check that.
Thanks

 

[Brian Roth]

After glancing at the block diagram, you can narrow down some stuff.

On bad modules, try both mic and the balanced line inputs to see if both/one/neither passes signal. Check to see if you have those sources appear at the insert jack. For that test, you'll need a TRS plug for the insert. I can't tell if tip or ring is the send from the preamp stages in the diagram That at least begins your troubleshooting.

Bri

 

[la80vette]

After glancing at the block diagram, you can narrow down some stuff.

On bad modules, try both mic and the balanced line inputs to see if both/one/neither passes signal. Check to see if you have those sources appear at the insert jack. For that test, you'll need a TRS plug for the insert. I can't tell if tip or ring is the send from the preamp stages in the diagram That at least begins your troubleshooting.

Bri

Will do.

 

[GeoffDoane]

I owned an early Crest Century GT (new in 1993). The major (only?) difference between the 3 models was the EQ section. The SP was 4-band fixed, the TC was sweepable mids, and the GT all 4 bands sweepable, with peaking or shelving on the upper and lower bands.

As Brian says, there are no electrolytic coupling caps in the audio path. Generally there is a servo op-amp before any switches to remove any DC. A number of these failed on my console, and I got pretty good at finding and replacing them. At least they put all the ICs in sockets.

The other problem that showed up as it aged was intermittent insert points on the back panel. Sometimes a shot of high level audio would punch through the grunge. I eventually made up some dummy plugs with tip jumpered to ring for channels that didn't already have something plugged into the inserts.

Good luck with this. It's a project for sure.

Geoff

 

[Growlhouse Recording]

Hi everybody. I'm resurrecting this thread to chime in my experience.

I picked up a century t about 6 or 7 years ago and am using it for recording, sending the direct out to my interface and when I mix, I'm sending stereo groups into the line ins to sum.

I've lost some channels and am now working on a project where I am replacing the mic/line switches and the faders as well as cleaning pots and switches with deoxit. This is purely for maintenance and having non intermittent signals.

In addition, I am researching how to upgrade this desk. I am mainly looking at how to use the xformer option, as well as seeing if there is a better op amp to put in. Any suggestions?

It is true you can only use a 1:1 transformer and it won't affect the color of the sound? I would like to be able to add character to the signal.

 

[LuisTstudio]

Hello everyone,

I'm writing in this thread because I've had a catastrophic failure in the PSU of my Crest Audio Century TC. This failure has burned and damaged the toroidal transformer. The damaged part is the primary side, so it's completely impossible for me to connect it to measure the three output voltages with a multimeter. The schematics (attached pic) only specify the following: V1ACA, V1CT, V1ACB, V2ACA, V2ACB, V3ACA, V3ACB, without stating the exact voltages.

I need to know exactly what those output voltages are so I can provide them to have a new transformer made.

Does anyone here who owns this mixer in working condition have the kindness to open their PSU and give me the multimeter readings for each of the secondary wires?

I know it might be a bit inconvenient, but I would greatly appreciate it if someone could help me.

Best regards, and many thanks.
Luis