70s Soundcraft Series 2 Console

[tchgtr]

If the pots have the square punch-hole in the back of the case, that can be a convenient way to introduce Deoxit.
Definitely replace the 'lytics, especially if they look original. Don't know about higher values.
Leave the ICs alone. That's a lot of work since they are soldered in. The 'lytics will make more improvement anyway.
If the green films are for the EQ, try replacing with some polypros. Maybe start with a stereo pair to see what you think. You'll like it.
From my limited experience, you may get a few busses working with cleaner. Be sparing with some quality stuff like the Deoxit. Operate a switch while looking at the back with a magnifier and you might see the contacts you want to spray.
Whatever you use to clean the faceplate, try a little of it over some out-of-the-way lettering to make sure it won't remove it. Clean the faceplate while the channels are removed.
Enjoy.

 

[W DeMarco]

Mike Gary Frank and everyone else that has helped me to get the 2nd of our series 2's working.....


IT WORKS!!!!


Frank(moneypit) sold me the guts of his old 2's PSU which Mike kindly stepped away from.  Between a bunch of his parts and mine the beast is finally working. 

Mike.  There arent too many parts remaining but if you need a torrid or 2nd small tranx I still have those(not even sure if they were the prob...long story) along with the heat sink and 3055.  Hope your diggin yours as well!

Will

 

[pcmurphypc]

Fantastic thread - especially as I am about to go through my 16 channel version.  I absolutely love this board - good pre's and the eq section is killer- I also have one section with the sweepable eqs.  I also have a 24 ch version too. I have 2 power supplies - 1 is shot and the other seems to be fine. So, I've never thought much about using more than the just one supply.  After reading this, I think I need to rebuild the busted one and bring it back to spec.  Can anyone give me some direction on recapping the supply - where to get the caps. Any other upgrades or repairs that I should make while she's apart? I'm also going to rehouse it in a fan cooled 19" rack with a power button on the front.

The led upgrade sounds nice - how is that accomplished and where can I get the led's

also, are you serious about putting the P&Gs in water? That sounds a bit crazy.

 

[W DeMarco]

Welcome to the DIY forum Murphy, prepare to be an addict!

Recapping your supply should actually be the easy part of your rebuild.  Some of these SC2 psu's are different than the schematics in the manual.  For example one of our supplies has one torrid and two can caps, the other has two transformers and three can caps for the 2 rails.  If you dont have the manual you can find it on soundcrafts webpage in the product listing under older products.  On the PCB you will find two electolytic caps valued at 220 uf 63 volts, I think the cans are 6800 uf.  Those you can find at mouser or digikey.  The diodes are pretty common as well and their values are listed in the manual.  The torturous part in the rebuild will be transistors as it seems other than the pass transistor(big one mounted to heatsink 2n3055) are no longer produced and almost impossible to find although there are some on ebay as we speak.  The tough ones to find are, 2sc1000(bl), 2sa493(gr) and bc300.  Other than those the rest is all resistors. 

As long as the water is deionized distilled you should have no problems with water.  Of course you should probably pull the faders if youre gonna get that meticulous and let them dry out very well. 

The led upgrade is really gonna depend on the voltage your VU lights are operating at.  I've never looked into that tho, maybe one of the other SC2 whores can comment on that.

Or you can sell us your 24 channel SC2! 

 

[W DeMarco]

Yanno that 2n3055 is the only thing that really heats up in the psu and as you know its attached to a giant heatsink which really dissapates the heat well.  I don't think you need to bother with the fan, its just gonna create noise in your rack and its really overkill.  If you want the really easy way to install a switch just plug the PSU into a power strip with a switch as it really accomplishes the same goal. 

 

[W DeMarco]

In light of the recent resurrection of the series 2 fanpage maybe one of the transistor gurus around here might be able to help us with some cross referencing.  I've gone to lots of sites to find cross reference replacements for the transistors and everyone seems to have a different cross.  Ive found, on one site, the 2sa493 crossed to a 2sc1000 which is strange as both are out of production and one is pnp and the other is npn.  I'm not too smart :'( about the specs and inner workings of the transistors and am kinda scared to make the jump to modern replacements without some help from the fellas.

Out of production transistors:

BC300-6 medium power NPN
2SA493(GR) small signal PNP
2SC1000(BL) small signal NPN

Cross Referenced by Gary and Smallbutfine:

BC300-6 medium power NPN : NTE154  (not yet tested)
2SA493(GR) small signal PNP : BC560C
2SC1000(BL) small signal NPN : BC550C

 

[gar381]

W DeMarco

bc550c npn and bc560c pnp should work fine for your small signal transistors and easy to get.  give them a try.

GARY

 

[pcmurphypc]

Ahh, its nice to have some folks that know what these things are about and can see the value in them. 

I'm gonna post some photos of the working power supply and maybe the bummed one (gotta get that one out of storage).  Maybe you guys could guide me through it a bit better.

I'll also post some photos of the 16ch board in its new housing.

Also, has anyone ever changed the preamp transformers to Jensens or Cinemags? Any difference - positive or negative?

 

[pcmurphypc]

Also, I have the original manual and schematics if anyone needs them

 

[smallbutfine]

You might try Panasonic FC for cap upgrade. Affordable, low esr and sound good.  If BC550C and BC560C work as a replacement in one channel as Gary suggested, go for it. They are quite cheap, standard but good european audio transistors.
You might try a NTE154 video output transistor as a cross reference for the BC300-6, but i am not sure if this works....

 

[W DeMarco]

Great stuff guys, Gary, Smallbutfine, many thanks!

I think I'm gonna have to change these transistors as something happened to the freshly resurrected PSU.  Bummer but I spoke too soon.  Ill update my transistor reply with this new info.

Murphy, considering that you have 40 channels in the end some modifications might be a fun idea.  Personally I never even thought about the transformers as theyre all sowter and pretty damn good.  Honestly tho, in my case, I rarely use the mic pres outside of on toms and room mics.  Maybe some gtrs here and there...  I like to keep the channels open for monitoring  and love all of the outboard pres we have.  However now that our 24 channel is semi running I think that might change. 

One of the latest question I havefound concerning the power supply is the dual transformers and the voltage selector switch.  Schematic is on page 67 of the manual PDF found here:  http://www.soundcraft.com/downloads/fetchfile.aspx?cat_id=user_guides&id=651 

If you notice on the top right of the schematic you find two transformers, one for the 40 volt rail and the other for the 48 volt rail.  The 40 volt rail tranx, the lower of the two in the scheme, is pretty obvious on hookup, neutral to neutral and hot to hot through the voltage selector switch.  However the second transformers neutral is connected directly but the hot connects on the voltage switch at only the 240 volt position.  How does the 48 volt transformer recieve the hot if I am running at the 110 position? Is the 240 position somehow inter related to the other positions on the switch?  I cant tell because I dont have the piece that holds the fuse inside of the switch and have no way to check continuity.

 

[gar381]

W DeMarco

On a quick look  it seems like the 48v transformer has a 240v Pri. It's using
the Pri of the lower transformer as an autoformer to always supply the pri of the
48v transformer with 240v regardless of the tap changer position as long as the
input voltage matches the tap changers setting.

GARY

 

[smallbutfine]

I suggest also trying BC141 in place of BC300-6, again, no warranty it will work.
I just tried to find quick guesses without having seen the schematic yet.

 

[pcmurphypc]

I opened up the working power supply and it looks like it needs some help - Any direction would be much appreciated.  One of the photos shows some replacement caps I found some time ago - I was told these would be the right fit.

 

[pcmurphypc]

another photo

 

[pcmurphypc]

the board

 

[pcmurphypc]

the back of the board

 

[pcmurphypc]

the replacement caps:

 

[W DeMarco]

Brenda must have been one busy gal as her name is on my pcb as well.  Im not sure about those replacement caps, the values are different than noted in the manual.  All 3 should be 6800uf at 63 volts.  I think the 10000 uf will be fine but those 1000's are a lower value,  you can always recap with a larger value if need be but a smaller value isnt a good idea.  If the working supply is working I would just recapp those 3 big cans and the 220 uf's on the pc board.  Don't worry about the discoloration under the diode bridge, ours looks the same.  Or if it is working maybe just leave it be.  As long as those caps arent leaking you should be fine. 

 

[man-bot]

Not to dig up an old thread but I didn't one to start a new one considering all the good info here...

How do you guys find the pres on this board?  I was doing some all analog tracking last night using the onboard pres to my Tascam 80-8 reel to reel and I'm finding I had to cut the top end to keep the hiss down... I don't seem to get as much noise when I use my Green Pres in the same set up.

Not sure whether its just a matter of playing louder as I was semi subdued but the hiss (w/ DBX on even!) was awful.

One other note - can anyone take a pic of their output board on the component side for me?  I am going to try and un-mod my outputs as they have a daughterboard attached using LM318s and 5534s.  I'd like to just use the original power supply and not have to continue using up my +/- 15v supply (well its just pulled off my green pres right now but I need ot restruture).  I can go by the schematic but having a visual is always nice...  Also am interested in hearing this bad boy work in its original state!

Thanks

Mike