ROYAL OPERA HOUSE CALREC REFURB

With a comprehensive range of mixing consoles, Calrec has been a manufacturer of high quality audio products since 1964.

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Re: ROYAL OPERA HOUSE CALREC REFURB

Postby Matt Syson » Mon Jul 05, 2010 4:58 pm

Hi
Ahh, I remember those supplies (not necessarily your units specifically).
The 2N3055's in the metal cans were so much more reliable than the (theoretically greater rated) plastic transistors the boards were designed for. Unfortunately if you shorted the outputs the transistors literally exploded with hot plastic flying.
The logic supplies use virtually unobtainable 10 Amp variable regulators so hope they are OK otherwise rework with a new regulator design would be necessary.
The plastic boxes contain the 'anti surge' circuitry, check inside for crispy components.
Good luck
Matt S
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Re: ROYAL OPERA HOUSE CALREC REFURB

Postby sebastian747 » Tue Jul 06, 2010 1:40 am

Matt thats great info thanks man...its really amazing that the guy who tested this thing ..A : still shows an interest and B: has a photographic memory. thanks.
What ever is in the black box is making a very strange noise ...we assumed it was a Relay, as we ramped the volts up toward 240 it stopped...sounding like the relay had fired, when we dropped the volts it came back in ...sounded like one of those VOOVOOZELA horns ...im gonna crack open the black box today for a look.
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Re: ROYAL OPERA HOUSE CALREC REFURB

Postby Matt Syson » Tue Jul 06, 2010 2:22 am

Hi
There were 2 versions of the insides of the box. One was a big resistor and a solid state relay which 'shorted out' the resistor after a short period of time. The other has a real relay to short the resistor which is what will be making the noise. It is powered from 120 Volts (from transformer centre tap). There is a 47uF 63 Volt cap to stop the relay 'chattering' which has most likely failed.
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Re: ROYAL OPERA HOUSE CALREC REFURB

Postby GJC Designs » Tue Jul 06, 2010 11:45 am

For your interest........

I get various Calrec PSUS through my workshop for repair / service / refurbishment. Some have had problems with the anti-surge cards, so I have designed a replacement which is often quicker or more cost-effective to install than to repair the problematic card, especially if the original card is damaged, overheated or otherwise not fit for service. Usually the cap and relay are the parts that fail. High-temperature caps are your friends.

If you have serious regulator problems and cannot get the 10A regulators that Matt has mentioned, it is possible to parallell LT1083 devices. Layout really is critical when doing this, but after a suitable amount of R&D I have a production design where I have got noise down below -85dBu with a 12A load.

Contact me if you need further info.

Cheers,
Gareth
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Re: ROYAL OPERA HOUSE CALREC REFURB

Postby sebastian747 » Tue Jul 06, 2010 2:20 pm

That's great thanks, I had the surge box open today and switched the cap out, popped the PSU on the variac and gave it some juice and all seemed well . Tomorrow however I'll run a dummy load on all the units to see how they cope, probably just 2-3 amps but enough to see if anything is on the edge of going bang before trying it with the console. Even if all is well I will recap the psu's and look at some options on the regs in the logic psu so that in the event of it going pop I have a plan ready in the wings to sort it, thanks again guys for the amazing In sight u have.Btw what was Richard lumbs envolvement with this desk I notice his name on many of the drawings and also as a moderator here?
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Re: ROYAL OPERA HOUSE CALREC REFURB

Postby Matt Syson » Tue Jul 06, 2010 3:04 pm

Hi
I am not sure I would worry too much about the logic supply regulators. I have a suspicion that you could probably run with LM338K regulators (officially 5 amps per device) as the desk will probably not take that much power normally and the principle of having several 'small' supplies would mean that there is significant redundancy.
The original devices may actually be available if you really look, I think I have one in my shed!
Try measuring the current taken when all is up and running to get an idea of whether it is actually a problem.
Incidentally the power inrush limiter box could probably be replaced by an NTC resistor, suitably mounted as they are intended to run hot and will have mains voltage on them.
Incidentally the inrush limiters were instegated when trying to power a desk at the BBC and as there were so many toroidal transformers we melted the 50 Amp breaker (estimated inrush of over 300 Amps). Running the desk on a couple of 4 way extension cables during factory testing was of course no problem due to the 20 metres of 'thin' mains cable!
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Re: ROYAL OPERA HOUSE CALREC REFURB

Postby sebastian747 » Tue Jul 06, 2010 3:33 pm

ha...love it, the idea of you guys chain ganging 4 ways...so its not just guitar players that do it?
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Re: ROYAL OPERA HOUSE CALREC REFURB

Postby Matt Syson » Tue Jul 06, 2010 4:16 pm

Hi
When the desks were being built they would be spread out on the wiring shop floor so the testing usually had to go to the desk and as they were often completely different sizes the layout changed each time.
Getting the desks downstairs (the factory had 3 floors) on a chain hoist was usually a 'fun' time too.

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Re: ROYAL OPERA HOUSE CALREC REFURB

Postby sebastian747 » Wed Jul 07, 2010 2:17 am

You should post some pictures if you have them. It would be very interesting to see. If not some pictures of your shed will do as i reckon you might have all sorts of audio treasure stashed away in there.
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Re: ROYAL OPERA HOUSE CALREC REFURB

Postby sebastian747 » Wed Jul 07, 2010 7:59 am

Ok so tested the power supplies on load this morning. Only one of the 4 audio psu's is clean, strange that it's the one with the caps that look most knackered??? The other 3 have HF oscillation that shows up on the scope ... The basic test was : 17.5 v run into a 4 ohm load = 4.4 amps per rail.
Logic psu has a bit of ripple & noise
The phantom has more ripple and noise ???? Anyway to to plug the console in ... Here goes!
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