Crest Century VX - Refurb project

[johnylondon]

Hi, new to this forum, just picked up a Crest Century VX 52 channel.
I took a bit of a punt on this one as it's without its power supply, but the price was too good to miss.

So, I will be posting a few snaps as I go along. The first thing was getting it up the stairs to my flat - took the channel strips out as they need servicing anyway, wow what a great thing this desk is.

So, on to the tech stuff...
Firstly, I'd appreciate any help getting hold of a pdf of the circuit diagrams - especially the PSU as I may end up building one.
Secondly... if anyone has a spare PSU going please let me know! (I'm in London by the way!).

What do you guys think about this desk? I'm pretty ok cleaning pots and soldering stuff, my main concern is if the vca groups are down, might be beyond my abilities.

But first I need to power it up and see what I have - I was thinking a bunch of switch mode supplies would be ok but have been told they could prove too noisy - any views?
Well, most likely I'll be searching ebay for something suitable.

Pictures to come soon!

John

[Bill@WelcomeHome]

never used one, but I checked them out at trade shows and spoke to one of the principles. It was very affordable, and appeared to be well-thought out. Good luck.

[Funk-O-Meter]

Hey Johnny,

Got your message. Here's where you can download the schematics:

******//www.groupdiy.com/index.php

You'll need to create an account and look in "The Lab" in the "Technical Library" section. Third page under Crest.

No PSU schemo's though I don't think. Maybe ask over there and maybe somebody can come up with them.

I wouldn't worry about the VCA's. They where robust as was the desk as a whole. You know if you picked it up Mine has been doing 25+ shows a month in the venue I'm the production manager for since I refurbed it. Since I finished going though it and found/fixed/replaced every little problem the only trouble it's given me are some dirty switches that I've cleaned, three bad LED's, and every once in six months a dirty high pass filter pot will oscillate and make noise until it's exercised then it goes away. The pots are sealed and I haven't had many problems with them. Dirty insert return jacks not normalizing correctly and worn out switches where the biggest amount of work. I did replace a few channel cards and one group card I just didn't feel like working on anymore. And even those worked well enough to use. Just that the meters where out and stuff like that. I'm just not into living with funky channels. I don't have enough time or patience to deal with that when I've got 3 band on a sold out night.

When I get the time and feel tweaky I'll get around to modding it

I really love the desk though. I really like the pre's and all the EQ. Sure there's better for recording but this desk is no slouch. And I can't mix without VCA's anymore.

Now the same guy I got it from wants to sell me his 40 channel Allen and Heath GL4. Man life is hard.

[johnylondon]

Hey thanks Funk-O-Meter, I'll check that link out though I really wanted the psu diagram... maybe I'll get lucky and find a working supply on ebay but anyway - as promised a few pics...

Here is the desk as I got it - the guys I collected it from loaded it into my van with a forklift...

(First thumbnail)

I had to take the channel strips out to make it light enough for a neighbour and I to carry up a flight of stairs and into my flat, but at least it fitted in pretty well into my existing studio/study...

(Second thumbnail)

A bunch of the channel strips...

(Third thumbnail)

And a couple more after I reloaded it - the strips are not plugged/screwed in yet...

(Fourth & fifth thumbnails)

All I have done so far is to clean off some stickers/tape etc, and re organise the control knobs - there are 4 odd channels that have the later (?) grey scheme P&G type knobs, and a few channels had odd gain knobs etc. I managed to put all the later knobs on the subgroup/master sections, and use the ones off for the channels. Everything looks perfect now, save for two or three odd channels at the far end and one or two knob caps the wrong colour in the middle.

Condition wise the desk is good - I have only found one switch that doesn't lock, there are two fader knobs and one switch cap missing, one channel has a sticky fader.

Of course - no psu so who knows what I will find come power up!

[johnylondon]

Hey I just found the schematic for the 4a/6a psu... it was on the Crest website all along.
They have Century GT and GTX but not vx - any ideas? Is one similar to the Vx?
Getting there...

[Jim Williams]

You can whip up a good linear power supply using Power One supplies. Just follow the designs grounding and voltage requirements and put them into a box. You may need to source the power connector to the console.

[johnylondon]

Originally Posted by Jim Williams

You can whip up a good linear power supply using Power One supplies. Just follow the designs grounding and voltage requirements and put them into a box. You may need to source the power connector to the console.

Yes, thanks for that - it was the sort of rout I fancied going really, until the proper thing one day turns up on ebay. As a start I have sourced a power one 24v supply - it's only the 4.8amp version but I can always run with a few channel strips unplugged. Still searching for suitable 20 volters.
I think I would need to ad an output fuse and clamp diode circuit though - wouldn't want to risk going over voltage and zapping all the ic's. (I see that power one do over voltage protection boards as ad ons for their psu's which could be handy)

Looking forward to getting the beast fired up

[Jim Williams]

Any of the Power One 24 volt supply can be trimmed down. Contact the apps dept. for specifics. It's as easy as adding a resistor across the voltage sense resistor to expand the adjustment range.

[graemeftv]

hi i can help you i have all the circuit diagrams and can provide info on power supply options.

[RogerCalifornia]

I had the pleasure of using a Century Vx from 2002 to 2005 and it was the best ever for live sound. Very reliable, quiet and predictable. I loved the aux's with the push-on, push off feature. The VCAs were awesome.
I never did any maintenance in it but it seemed well designed.
Best of luck getting it running. Somebody might put a power suppluy on ebay. Set an alert just in case.

[johnylondon]

Well I have been making a bit of progress with the desk - I used a couple of Vero eurocard smps for the +/-20v. When I got them I had expected to have to make up regulator circuits to drop them down from 24v, but surprisingly they adjusted down JUST far enough (20.5 and 20.6v), which saved a bit of effort and means I'm benefitting fully from their o/v protection etc. I had been advised against going the smps rout - for the sake of any noise they might introduce - but these quote very low ripple for this type of supply (40mv p-p) not quite as low as a linear but still not bad. Anyway - amp up full with no signal and all I got was a little analogue hiss so I'm pretty happy with them. The power one is doing the 24v. No 48v as yet though.
Anyway - no real problems appart from the tiny square switches that often need switch cleaner and a good bit of working to clear - the led lights stay on until you get them right.
Found a handfull of duff switches (not locking) but only a few so far. I've got a couple of subgroups that rarely work (that is, their o/p isn't making it to the l/r bus) but should be traceable.
It's a nice desk - a smooth and warm sound, quite clear but not cold.
Will have to do quite a bit of new cabling thanks to the way the inserts are wired but what the heck.
By the way - I might just be being stupid but I can't get anything out of the oscillator/pink noise generator? It's probably bust unless there's some trick to it.
Happy days

[DrSound]

Originally Posted by johnylondon

Well I have been making a bit of progress with the desk - I used a couple of Vero eurocard smps for the +/-20v. When I got them I had expected to have to make up regulator circuits to drop them down from 24v, but surprisingly they adjusted down JUST far enough (20.5 and 20.6v), which saved a bit of effort and means I'm benefitting fully from their o/v protection etc. I had been advised against going the smps rout - for the sake of any noise they might introduce - but these quote very low ripple for this type of supply (40mv p-p) not quite as low as a linear but still not bad. Anyway - amp up full with no signal and all I got was a little analogue hiss so I'm pretty happy with them. The power one is doing the 24v. No 48v as yet though.
Anyway - no real problems appart from the tiny square switches that often need switch cleaner and a good bit of working to clear - the led lights stay on until you get them right.
Found a handfull of duff switches (not locking) but only a few so far. I've got a couple of subgroups that rarely work (that is, their o/p isn't making it to the l/r bus) but should be traceable.
It's a nice desk - a smooth and warm sound, quite clear but not cold.
Will have to do quite a bit of new cabling thanks to the way the inserts are wired but what the heck.
By the way - I might just be being stupid but I can't get anything out of the oscillator/pink noise generator? It's probably bust unless there's some trick to it.
Happy days

May be this will be suitable.

[johnylondon]

Thanks for that! It's quite different to the psu diagrams I got from the Crest website for lmx20 4 and 6 amp psu - I assumed they would all be similar.
I have built a supply from Vero switched modes and a power one now - seems to be working well.
Next stop a few replacement switches!

[johnylondon]

A quick update - All working ok now, minus the last dozen channels which I have left out due to psu limitations (the set I have do 5 amp each per rail so I'm an amp short everywhere, but have aquired 2 more linear modules, just waiting for a third to come along then I can build the mk2 all linear supply... and put the rest of the strips in!).

Anyway, intermitent subgroup and master channels turned out to be the ribbon cable connectors - I'd already crimped them up a bit more before refitting things, but gave the offending plugs another nip with a vice and a good spray of switch cleaner and that seems to have sorted them. Just a few switches to replace now... and one led on a strip that stays on (vca overload).

I made all the trs cables etc so my whole set up is nearly running again.

Funk-O-Meter - I saw you found switches, can you offer any advice? I need 5x 12pin grey, 2x 6pin grey, 2x 18pin grey. Just had a look on ebay and I'm going to order these...

******//www.ebay.co.uk/itm/PS909L-62-...80039520716073

and these...

******//www.ebay.co.uk/itm/PS909L-42-...92267830864861

They look exactly right, pity theres no 6 pin (2pdt) ones.

Also I need a couple of faders (100kb) Anyone know what the faders are... P&G? Maybe ebay will have the answer...

Can't wait to make some music with this thing

[johnylondon]

Well, all the new switches are in and working - was mildly concerned that the contacts appear to be silver rather than gold but I guess they will last long enough... especially if used regularly. What a pain getting the old ones out though - it was a destructive process.
There's just one vca light that stays lit (red=overload) on a channel, otherwise everything is perfect now, and I'll have a look at that when I get a chance - been too busy laying down some tracks

I noticed that things are a little out of cal though - saw a couple of presets on the circuit boards namely DC Trim and Dis (channel strips) don't sound like they are the right thing for gain adjustment but really its only a db or two here and there (according to the meters anyway!) I can live with that.

Oh one other thing - I've been busy making up desk sheets for this - so if anyone would like me to send them the word document of it just pm me!

[Th3_uN1Qu3]

DC Trim is DC offset adjustment, check with a multimeter before adjusting, it may not need adjustment at all. Dis, i have no idea what that stands for.