Soundcraft 600 Restoration

Founded in 1973, Soundcraft first made its mark with the launch of the Series 1, the first mixing console in a flightcase.

Moderator: GJC Designs

Soundcraft 600 Restoration

Postby Gonecat » Fri Mar 14, 2014 9:55 pm

Got the 600 yesterday for super cheap; just made space for the beast today and opened up the packaging. She's definitely in some rough shape in spots. And so, the restoration begins!

It is a 32x8x2 desk with the full patchbay. The dimensions are roughly 3' deep, 5'6" wide, and I think it's about 1' high in the back. With 20 modules removed and not including the PSU it said on the UPS slip that it was 150lbs. Felt like it, too.

Image

The good news: I haven't fully checked it out, but on first inspection I am pleased to find that it actually works, kinda. Aside from some intermittent buttons, the PSU's 48v light doesn't come on. I didn't try a phantom powered mic on it.

Image

I instantly loved the preamp and eq on a quick vocal test with a dynamic mic. Coolllllllllll!

Image

Also, the noise did not seem bad at all (I am coming from Mackie/Behringer hell so my standards are profoundly low). Again, this was just a quick check.

So, the bad news: The 'wood' sides are flaying (and some bad packing resulted in the back corners getting jacked up).

Image

There is rust in the chassis, and on the nuts and washers of the pots. It was an east-coaster now in the dry desert air of Los Angeles. I swear I can smell the salty sea air in the chassis.


However, the PCB's look super clean and no immediate signs of anything funky going on with the 20 channels that I looked at.

The channel strips say "5101" at the top. Printed on the PCB's were "APW 8901" and "SC1491 Iss 9".

Image


Some initial question:

1) What's best way to tell what version of the 600 this is? I didn't see anything printed anywhere on the back. Since version 7's and higher have the trans-amp mod, I was curious.

2) Also, is the one with a patchbay known as the 'producer' version?

3) I haven't opened up the PSU yet but I'll need to look into this 48v issue and I'm assuming a recap will be in order. Any suggestions on upgrading those (higher value, higher voltage)?



Since I am someone who never, ever sells any music gear, I am cool with doing mods that make some people cringe, but then, how many of them still have the Korg Poly-800 they bought in 1986! (I'm going to do the VCF mod on that, soon ;) )

My plans for the board so far are these (open to recommendations!):

1) Put all modules in and do a cursory test, mark each channel's issues, order parts
2) Clean everything (chassis, knobs, pots, buttons)
3) De-rust and repair the chassis, fix the wood sides, put some funky faux leopard print leather on the arm rest
4) Repair any faulty switches, etc, fix/upgrade components of PSU
5) Grounding mod.
6) Re-assemble and fully test the board to get some benchmarks, etc.
7) Assemble the edac connectors/cabling (realllly looking forward to that).
8) Add 1/4" inputs to the back of the board for 16, maybe 32 channels (might do this earlier)
9) Trans-amp mod on 8-16 channels.
10) Recap channels as I go
11) Maybe upgrade the IC's and transistors on 2-4 channels to hear the difference
12) Add input transformers to 2 or 4 channels.
13) Dial in the EQ on two channels for Kick and Bass (might instrument-target some other channels one day, it's a crazy idea of mine since i always record the same instruments)
14) If possible, use those two blank panels to install LED meters for each of the 32 channels. Thoughts on this, anyone?!
15) Hopefully, record some music with it :-)

Anyway, thought I would document my trials and tribulations here for any other souls who venture into a project of this nature armed with soldering gun and ready to pop a few caps in a Soundcraft 600.


The connectors:

Image


Curious buttons - this was in a production truck before and there is a 6-conductor cable coming out of the board, I assume for these buttons:

Image


Back panel:

Image
Gonecat
VU Meter Specialist
 
Posts: 46
Joined: Mon Jan 27, 2014 8:59 pm
Location: Los Angeles

Re: Soundcraft 600 Restoration

Postby GJC Designs » Sat Mar 15, 2014 3:13 pm

It looks like a fun project. Technically the 600 is an easy console to work on so there should not be many difficulties to overcome in getting it back to full working order.... the aesthetics look to be the biggest challenge. :(


In reply to those of your questions that I have answers for:

1) What's best way to tell what version of the 600 this is? I didn't see anything printed anywhere on the back. Since version 7's and higher have the trans-amp mod, I was curious.
Look for the SC number on the PCB, typically SC1234 Iss5. This is the card's unique identifier and issue / revision number.

3) I haven't opened up the PSU yet but I'll need to look into this 48v issue and I'm assuming a recap will be in order Very wise.. Any suggestions on upgrading those (higher value, higher voltage)?
Technically there is no need for higher voltage caps. Some cap values may only be available in higher voltage ratings, in which case there is no option but to fit higher voltage parts. With regard to values, there is merit in increasing cap values in some places. It's likely that Jim Williams will chip in with his recommendations.

3) put some funky faux leopard print leather on the arm rest Cool!!! Photos will need to be posted!
6) Re-assemble and fully test the board to get some benchmarks, etc. How about this as the first technical goal so as to get the benchmark before and components are changed or grounding mods done? You will then have a known set of references to compare to.
8) Add 1/4" inputs to the back of the board for 16, maybe 32 channels (might do this earlier) Be aware that the tape return EDACs feed into the channel line inputs via the patchbay, and that the ribbon cable from the patch to the channels goes via a PCB on the rear panel..... probably just where you will be wanting to put your jack sockets.
9) Trans-amp mod on 8-16 channels. The additional components may present a challenge with regard to where they go. Jim has more experience with this mod than I do so best check with him for recommendations
10) Recap channels as I go For the low cost of the parts, and the time wasted in taking modules in and out of the desk time after time, consider doing the recap when you have the modules stripped for cleaning
14) If possible, use those two blank panels to install LED meters for each of the 32 channels. It's unlikely that your present PSU will cope well with this. My desk (32-8-2) is customised with LED meters on all channels and the direct outputs are balanced. The PSU gets a bit too warm for comfort. The desk has the originally designed-in chips, so the standard audio circuitry is pulling no-more current than it should.

Keep up the updates. I'm looking forward to following your refurbishment project as and when I am able to drop-by here.
Gareth
GJC Designs
Yacht Rocker
 
Posts: 304
Joined: Fri Oct 13, 2006 12:39 pm
Location: West Yorkshire, UK.

Re: Soundcraft 600 Restoration

Postby Gonecat » Sat Mar 15, 2014 4:59 pm

Thanks Gareth!

Good point on doing the benchmarking first, i was just figuring that the cleaning and grounding mod would put it at a zero point from which i would compare the different mods (even re-capping a channel), but I'll do it first, at least to have reference for what the grounding does.

The input channel PCB says "SC1491 Iss. 9". I searched around for it but didn't find much info. Would the Iss.9 be the version?

Regarding the LED meters for the 32 channels, it's just a thought at this point, but down the road i will probably obsess over it. Good point you make on the power, I reckon i could just run a wallwart or seperate PS. Wasn't planning on doing many IC swaps so if i can just refurb this PSU i hope to be ok. Not to mention how pricey bigger PSU's are...whoa. Do you happen to know where your LED's buffer circuit is tapping the audio?

1/4" inputs - thanks for the heads'up. There seems to be some space. After working on little guitar pedals this thing seems like an airplane hangar.
Gonecat
VU Meter Specialist
 
Posts: 46
Joined: Mon Jan 27, 2014 8:59 pm
Location: Los Angeles

Re: Soundcraft 600 Restoration

Postby Gonecat » Mon Mar 17, 2014 12:53 am

I assembled the board and ran some basic tests (I don't have any 'real' test equipment, though I am curious what can be done with a laptop as test device). I used a dynamic mic, headphones, pen, and paper.

Image

About 21 of the channels checked out "ok". As in "I could record with it now".

The main problems I encountered with the other channels amount to:

Intermittent buttons.
1 or 2 bad buttons.
1 fader fairly jammed up.
PFL not working on 2.
Not passing signal to bus on 2.
Low noise but low gain.
Dirty pots.
Probably some bad connections on 2-3 modules.

One module did have this crazy white corrosion going on, what is this and how do I clean it?!:

Image


Along with warm water and dish soap I removed and soaked some 466 knobs. After swishing them around together for 5 or 10 mins the dirt seemed to brush right off. Colors are shining again! I used a eyebrow brush but a regular toothbrush would be best. Letting the 'dirtier' ones soak over night.

Image

On the channels that were good I was really surprised how much gain and how little noise i could get. Scary really, and even with closed-ear headphones it would feedback before i noticed extreme noise (sm58 knockoff mic).


I guess since these input modules say 'Iss. 9' that I have the trans-amp mod already done?! I will have to check the schematic for that mod verses what is on the PCB tomorrow. Though I have not yet confirmed what version this board is.

A couple questions for SC600 USERS:

How do you test the 9-16 meters? (When i power on or off, all 16 do the same thing visually)

How does the 16 channels of tape i/o even come into play?! Just via the patchbay?
If i want to send out to those 16 tape channels, how is that even done?

I did read the manual, a few times, and i guess i didn't grasp the concepts on this one!


A couple questions for SC600 TECHS:

How do i clean the rust from the face plates that surrounds the pots?

All nuts and washers (as in, 466 of them) are rusted. What is the best place to order those and what size? (I can figure this one out with some research, but does anyone know off hand?)

Image

I was taking a look at the schematics and thinking about the LED monitoring of the 32 input channels. What about this: a 3 position 16 pole switch (seems they do in fact make them) that switches between the normal 16 inputs to the LED's (the buses and tape returns) and input channels 1-16 and 17-32? That way no extra power is needed from PSU, no front panel changes are needed, and it skips the $100+ in parts for doing dedicated 10-segment LED's. Just a thought; I wouldn't mind a 3 position switch for that.


All 466 pots seem to function good to fine. Almost all buttons worked with some rapid button-pressing. All but 1 fader works just fine. All EQ sections worked fine. All XLR jacks worked.


I looked into some faux leopard leather but i either couldn't find any or it looked like David Lee Roth leotard, not leopard. Anyway, decided to just 'cover' the side wood panels with some pleather instead of fixing/replacing with heavy ass wood. Lighter, easier, cheaper, looks cool. Since the face plates are 'bluish", I photoshop'd this up:

Image

And finally, my 15 month-old niece with chocolate covered face has found the 'rock 'n' roll' button. Yeah!!!:

Image

She already knows how to slide faders, push buttons, turn knobs, strum guitars and hit keys...start 'em young!!!
Gonecat
VU Meter Specialist
 
Posts: 46
Joined: Mon Jan 27, 2014 8:59 pm
Location: Los Angeles

Re: Soundcraft 600 Restoration

Postby Gonecat » Mon Mar 17, 2014 1:21 am

By the way, the master section has IC holders for all IC's. Was that normal? The chips seem to all be TL072 and NE5532 so this seems odd.
Gonecat
VU Meter Specialist
 
Posts: 46
Joined: Mon Jan 27, 2014 8:59 pm
Location: Los Angeles

Re: Soundcraft 600 Restoration

Postby GJC Designs » Tue Mar 18, 2014 2:58 am

SC1491 Iss. 9 This will be the PCB issue, which means that the matching schematic will be at least issue 9, probably higher. When a component value on the schematic changed, the PCB issue did not change; when the circuit design changed, the schematic and PCB issues changed, hence the lack of sync.

Pot nuts are called something like M7 half-nuts.

TL072 and 5532 chips are normal; the schematics will confirm this.
TL072 used for general op-amp stages, 5532 used for low-noise or output drive stages.
Gareth
GJC Designs
Yacht Rocker
 
Posts: 304
Joined: Fri Oct 13, 2006 12:39 pm
Location: West Yorkshire, UK.

Re: Soundcraft 600 Restoration

Postby Gonecat » Tue Mar 18, 2014 7:05 pm

Thanks Gareth!

Does anyone know what, besides the 'trans-amp' mod, was done on version 9?

So, I only saw one manual for the 600 on the Soundcraft site. I guess I should be looking for a version 9 schematic somewhere?

The master board says Iss. 5, by the way.

Regarding the IC's on the master channel, I was ref'ing to the fact that they have IC holders already in place, to swap chips out easy. Was that normal?

Doesn't look like it was mod'd or this person was the greatest solderer the world has ever known. I did know about the TL072s/NE5532s being the stock choices.

If anyone has any ideas on how to clean the rust from the front panel without jacking up the printing, please let me know.
Gonecat
VU Meter Specialist
 
Posts: 46
Joined: Mon Jan 27, 2014 8:59 pm
Location: Los Angeles

Re: Soundcraft 600 Restoration

Postby GJC Designs » Wed Mar 19, 2014 12:34 am

The fitting of sockets had nothing to do with chip swapping or upgrades. It was done as an aid for servicing. Soundcraft had a policy of fitting sockets to double-sided boards that had plated-through holes. The aux master PCB and LED meter PCB should also have sockets fitted. Single sided boards such as the input channel and VU meter driver card did not have sockets.
Gareth
GJC Designs
Yacht Rocker
 
Posts: 304
Joined: Fri Oct 13, 2006 12:39 pm
Location: West Yorkshire, UK.

Re: Soundcraft 600 Restoration

Postby Jim Williams » Wed Mar 19, 2014 11:37 am

Remove rust off of nuts with a wire brush. There are no 'trans-amp' versions of 600, there is one in a schematic but that was never released. You would need to remove then add parts to the rear of the pcb, phase response tuning is essential for stability. Lower noise input transistors and opamps will help. The rest of that circuit can be direct coupled with the proper low offset opamps.

Usually switches need replacement for crunchy-less operation. That white stuff is solder flux that was not removed during cleaning. A good solder flux remover and a toothbrush will clean those pcb's right up like new.
Jim Williams
Audio Upgrades
Jim Williams
Yacht Rocker
 
Posts: 362
Joined: Mon Jul 14, 2008 9:58 am
Location: beautiful Carlsbad, CA

Re: Soundcraft 600 Restoration

Postby Gonecat » Wed Mar 19, 2014 3:01 pm

Thanks to you both for the info!

So Jim, regarding the trans-amp, this is the post of yours I was ref'ing to, so I'm a little confused now as to what you were saying was 'already there' on ver.7 and up:

It's a rather simple mod, you remove the 22k resistor and 100 pf cap in the opamp's feedback loop. Connect the 22k resistor with a 10 pf cap across it to the transistor's emitter, the transistor that feeds the - or inverting input. Don't connect to the non-inverting (+) input or you create an oscillator! Change the 100 pf cap from the non-inverting input to 10 pf, that open's up the bandwidth to 200k hz. You may need a small phase lag cap across the opamp's inputs, a 220 to 470 pf cap will usually work. That up's the phase margin so the opamp remains stable.
Or, get a ver. 7 or higher 600, the changes are already there.


Original post is here: http://www.gearslutz.com/board/geekslutz-forum/262911-trans-amp-mic-pre-mod.html

Amazing to have your input, gents, thanks a lot.
Gonecat
VU Meter Specialist
 
Posts: 46
Joined: Mon Jan 27, 2014 8:59 pm
Location: Los Angeles

Next

Return to Soundcraft Recording Consoles

Who is online

Users browsing this forum: No registered users and 1 guest

cron
 
Mr Patchbay sells patchbays, tt/bantam cables and more