Remake Power Supply for EAA Broadcast console.

[p0ulp]

Hello there,

I get my hand on a pretty nice mixer named EAA Quest 1600 , I ve been looking for information everywhere and finally get the tech manual from someone.  Though it's not the dedicated manual (it's for a Quest 804) , this quest serie looks a lot like a modular console.
I ve opened it few weeks ago to look for voltage, estimate de power need etc ...

Anyway, the schematic is straight forward, the manual also contain a bad copy of the PCB layout and a BOM , wow can't dream of a better situation.

So you might want to know what would I ask here ... well, I m not really a designer and if I m mainly able to understand the psu circuit of this one I would like some help to fit that PSU to my mixer (double number of track, so double number of IC + bus routing option etc ...) . By the way this mixer is almost 30 years old, and maybe some component could be replaced and other are not in production anymore (it's full of TL071 !!) ?

At the end, while I look the schematics it really doesn't look original, and maybe there are better circuit to achieve this now , I ve started looking at LM350/LM333  but never used before they are given for 3A output ? I don't really know if I should stick to the original .

I don't want to commit hundred's of euros in this, I suppose it's a really good mixer (used in radio france likes studer, schlumberger etc ...) but I m not to keep it, it takes a lot of space , it also got a really strange EQ that I would give a shot.

http://edouardfranqueville.com/quest1600/alimentation-EAA-Quest-804.jpg
http://edouardfranqueville.com/quest1600/alimentation-EAA-Quest-804-2-.jpg
http://edouardfranqueville.com/quest1600/EAA-Quest-804-Documentation-Technique-28.jpg

And the beast

 

[Niketouille]

Hi,
I had a 8 channels version of this console and repaired a 16 ch.
Bad ic socket, dry caps and dirty switch, nothing fancy.
Preamps are good, (input xfrmr is Melodium iirc) and eq is 3 bands, 1 fully parametric and 2 fixed freq shelving eq.
I decided to have the preamps and the eq racked. Also I think the psu used in the rack is something very typical with 78xx series.
Anyway good luck, it is a good console.
Cheers
G.

 

[PRR]

The original power supply plan shown in your alimentation-EAA-Quest-804-2-.jpg image is reasonable and should be adequate. I suggest you fix any faults and use it as-is.

The LM350 is a big version of one of the standard 3-pin regulators. You can re-invent this power supply with chip regulators, but... why? Also the LM350 is getting hard to find.

The supply delivers +/-30V (bipolar), +/-18V (bipolar), and a single "+15V (Fantome)". If that means what I think it means, it is not the P48 Phantom generally used today. However many-many Phantom mics run fine on 15V. There are a few (both high-cost and low-cost) which "need" about 48V for capsule bias; others include a voltage converter in the mike (or are electret).

The +/-30V (bipolar) seems to be fused for 0.5 Amps.

The +/-18V (bipolar) seems to be fused for 2 Amps.

The main filter cap sizes seem appropriate for these currents.

The "Fantome" supply current is not specified. The 4,700uFd cap might suggest high current, but the D510 1N400x diode spec means it can't be over 1 Amp. If this is just for Phantom Mike supply, 8 mikes at 10mA each is under 0.1 Amps.

If this is P15 phantom power, and you want P48, you need a 48V supply, *and* you need to check all the Phantom resistors and any caps to meet P48 specs.

 

[PRR]

> it's full of TL071 !!

An excellent audio amplifier, if used appropriately. I would expect a beefier chip or buffering at line outputs.

TL071 is out of fashion (TL072 is now the same price for twice the amps) but replacements are not hard to find. If they truly vanish, you can cobble a TL072 onto a DIP-8 header to work in a TL071 socket. (Unless it *needs* offset trim, which is unlikely.) However I have never seen a dead TL07x.

 

[p0ulp]

thank you for your answer, so I stick to the original circuit and no fancy upgrade .

The phantom  is written 48v on the back of the mixer, so maybe there is a step up circuit in the mixer I haven't look at it yet .

For the transfo any 2x18 / 2 x 30 / 1x15v  who can deliver enough power is fine ? the spec of T501 is not written in the part list, and as I said I m more familiar with LM78xx regulated psu and as I don't see trimmer to adjust the output voltage nor voltage divider to set the right output value, I m not sure if there is any multiplier factor ( √2)  for this type of design ... or maybe +/- 2 volt out of spec is not a problem and I m too picky/iPod generation/µV tweeker

Niketouille, I may have misunderstood the frontpanel but mine is a 2 band (Bass/treble) , treble is parametric and the third pot is a "Presence" or something like this, and there s a hipass on the input section don't know cut frequency it'es written nowhere  .. I don't have it under my eyes right now .

Did not thought to rack those pream, I mainly do line level (electronic synth) music, but maybe it's a good idea for some occasional bass / voice recording

 

[p0ulp]

Ok so I ve copied the schematic and decided to go for 3 different board because my home etching skill are not that great and I think  that with the current flowing through those board I should make big trace too, anyway I think of a 2U rack to host that PSU because I have one lying somewhere, so space is not a problem.

I didn't find a lib with the correct transistors BD 439/440 so I took the first To220  for each package to make the layout.

Also if this psu fit a 804, I m not sure it will fullfill the 1600 requirement in term of power consumption, so what part do I have to upsize to be sure that the mixer will not fries the psu ?

Complete PSU circuit , that I divide in 3 boards :
http://edouardfranqueville.com/quest1600/complete-psu.jpg

any suggestion is very welcome, I m not used to do this  as you can guess

 

[Paul-o]

Hi,
I repaired three EAA consoles since 2009. The biggest problem was bad Schadow switches, and some dry caps.

I like their sound and I did the job without the schematics. Would you please scan and post here some of the schematics ? I think it could be useful for all the community.

Thanks

Paul-o

 

[p0ulp]

Hi paul, all schematic are in this pdf file,

http://edouardfranqueville.com/quest1600/EAA%20Quest%20804%20Documentation%20Technique.pdf

 

[Paul-o]

Many thanks. You made my day.
Paul-o

 

[psych60s]

Hello guys

It seems that the schematics are gone... Someone kind enough to post them again? I have to check one of those beasts

Many thanks

 

[biosynth]

please

 

[sam system-d]

Please too 

 

[PRR]

> Here is a link :

That page opened several pop-ups, that I could not close, saying I had a virus and must call MicroSoft "toll free". It also used ALL the memory in my PC, slowing it to a crawl. Took 5 minutes to force the browser to close.

 

[sam system-d]

Ok, that's weird, it's my personnal mediafire storage place.
Very sorry for the trouble PRR and other forum members who would have experienced the same.
The doc is a 35Mo pdf, with all you need to know about the EAA console.
Do you have a better way to put such a doc online ?


EDIT :
I've been using that online storage site since ages, never had any problem with it.
Just did an analysis on my computer with bitdefender, no malware, no virus, no nothing.
I really don't get why you had problems.

 

[PRR]

That was FireFox. I tried again with Chrome. I got a different rude action (new window with strange ad in it). So MediaFire is "adding" pop-up ads to public download pages (maybe not on the owner's view of the page). The fact I got hit with an unkillable popup may be a combination of bad luck (some advertiser inserted a bad ad and MediaFire didn't detect it yet) and other factors.

I'm sure you didn't do it.

I am 99.9% sure my PC wasn't, and isn't, infested. But it was dang annoying for a while.

 

[sam system-d]

Well, sorry again for the trouble.
I've uploaded the same thing on my google drive.
Here is a new link :

EAA quest docs

Hopefully no trouble this time.

 

[ivanbass]

Well, sorry again for the trouble.
I've uploaded the same thing on my google drive.
Here is a new link :

EAA quest docs

Hopefully no trouble this time.

Hello, I just found about that discussion, I just got a EAA quest 1600 mixer without the alimentation bloc and I would realy apreciate to have acces to the schematics... thanks
ivan

 

[sam system-d]

there you go.
+/- 30v
+/-18v
+15v (phantom)

 

[Matt Syson]

samsystem-d Your sign off is a little curious when using google translate, unless you are a contortionist.
As with all op amps, you have to understand their good and bad points and design around them as appropriate. The TL071/72/74 are pretty indestructable but not good at providing a high output current which is sometimes needed for 'audio' work. loading them with less than about 2.5 K Ohms is a bad idea if you want low distortion for example.