Allen And Heath system 8 MK II RECAP Project

[The Convicted]

So I decided to just go for it, and recap the entire board. I want to post pics and anybit of information I can to help other members who have the same board.
I obtained the scematics from here:
http://www.allen-heath.com/veterans/...0issue%202.pdf

I will post the part #s of the capacitors, on the next post(I forgot the sheet @ work). The are all Either Panasonic FM or FC caps. Ordered from Digikey. Cost around $50.00 for all of them.

Also I ll start posting pics on the next post.

[The Convicted]

These are all the electrolytic Caps Used in the System 8 MKII. This includes the channel strips, busses, and master section. The Quantities I ordered are more than I needed, its always nice to have extra.

P10321-ND 47uf/50v Elect FC Radial Cap 50qty

P10220-ND 220uf/10v Elect FC Radial Cap 30 qty

P12923-ND 47uf/25v FM Radial Cap 110 qty

P12924-ND 100uf/25v FM Radial Cap 50 qty

P910-ND 10uf/16v KG Radial Cap 200 qty

I started to disassemble the board Yesterday, flipped it over and took pictures. I started by cutting the buss bars. I cant stress enough how necessary a desoldering iron is, don't attempt the job with out it.
I pulled up one of the strips and documented the polarity (or direction the caps sat in the circuit board). Take lots of pictures.
I pulled the caps from four of the channels cleaned up and called a day.
That was about 2.5 hours.

Today, in 30 mins, during lunch, i pulled four more. So I'm up to eight.

[The Convicted]

INSIDE

[The Convicted]

Cut and Desolder Buss Bars, (Redo all of them later), Replace with tinned copper wire .025" thickness.

[The Convicted]

Closer Shot of input channel, all the blue capacitors are the electrolytics, which we are replacing. I might change the ceramic caps for mylar, as another member suggested. There are 12 electrolytic caps per channel.

[The Convicted]

Desoldering. It goes by very quick. As soon as the solder melts, suck it up. Leaves a nice clean hole when it comes time to install new caps.

[The Convicted]

Sorry wrong pic on last post.

[The Convicted]

Input Channel with electrolytics removed. I marked a + sign on circuit board just as a reminder to put the caps in the right direction. Ill also leave on strip fully together until Im finished with all the channels just as a reference.

[2N1305]

wow, you're doing a great job here! The photos and descriptions will serve the newcomers really well. You didn't say though, that you have access to a really nice, professional desoldering tool. We see the rip in one of the pictures. Nice!

You know, what you could do too, at least on one of the channels, is put a nice machined DIP socket to be able to experiment with opamps.

2N

[vince @ speck]

Why just the caps?

Since you have the PC boards removed, how about replacing some of those old 5% resistors with 1%. There are a few circuits that could be improved with 1% resistors.

[The Convicted]

Originally Posted by 2N1305

wow, you're doing a great job here! The photos and descriptions will serve the newcomers really well. You didn't say though, that you have access to a really nice, professional desoldering tool. We see the rip in one of the pictures. Nice!

You know, what you could do too, at least on one of the channels, is put a nice machined DIP socket to be able to experiment with opamps.

2N

Thanx 2N
I really appreciate all the advice and help youve given me via, PMs and stuff. Since this is the 1st mixer Im attempting your info helped me get a hold of all those caps. By the way the Desoldering Iron was 10 bucks from radio shack, it works awesome!
I thought it would be cool to document my progress as I went, to help others DIY recapping.

[The Convicted]

Originally Posted by vince @ speck

Why just the caps?

Since you have the PC boards removed, how about replacing some of those old 5% resistors with 1%. There are a few circuits that could be improved with 1% resistors.

Thanx Vince for that bit of info, Ill look at the scematics again and most likly change those resistors on 8 of the channels.
Im Replacing all the ceramics for WIMA polyester and polypropolyne caps on Channel 1-8. Channel 9-16 Im just recapping and leaving those stock.
Thanx Again

Which resistors would benifit in this circuit?

[2N1305]

Originally Posted by The Convicted

Thanx 2N
I really appreciate all the advice and help youve given me via, PMs and stuff. Since this is the 1st mixer Im attempting your info helped me get a hold of all those caps. By the way the Desoldering Iron was 10 bucks from radio shack, it works awesome!
I thought it would be cool to document my progress as I went, to help others DIY recapping.

You 're very welcome, I never thought my simple advice would be received so well!

10$? At radio shack? They still have... Oh right the USA still has Radio Shacks...

We have The Source. they sell solder, one type of iron, connectors, fuses and a couple of other things... Ah, memories...

I remember when I was...
ah forget it.

[2N1305]

Originally Posted by The Convicted

Thanx Vince for that bit of info, Ill look at the scematics again and most likly change those resistors on 8 of the channels.
Im Replacing all the ceramics for WIMA polyester and polypropolyne caps on Channel 1-8. Channel 9-16 Im just recapping and leaving those stock.
Thanx Again

Which resistors would benifit in this circuit?

I know it isn't really my place to answer, but I figure Vince will say the resistors in the EQ circuit or around the Mic opamp, especially the ones that go from + and - inputs to ground. Oh wait, they probably are already 1%.

Nevermind what I said. Let the pro answer, I need my schematic!

[The Convicted]

Ill be posting more pics soon, but my progess now, Ive recapped all 16 channels, and the master section. I have to do the 8 buss section and Im waiting for the WIMAs to finish up channel 1-8.
I also took the cover off the power supply and I found a smoking gun. One of the caps on I think the phantom power circiut exploded. So Im ordering new caps for the power supply as well. I have a grand total of 8 hours into this project!

[The Convicted]

Originally Posted by 2N1305

You 're very welcome, I never thought my simple advice would be received so well!

10$? At radio shack? They still have... Oh right the USA still has Radio Shacks...

We have The Source. they sell solder, one type of iron, connectors, fuses and a couple of other things... Ah, memories...

I remember when I was...
ah forget it.

Just order it online 2N, even if the shipping doubles the cost, it is so worth it in time. You can quickly remove solder joints and it leaves a nice clean hole without heating up the board to death. Im using this cool flux, I dont remember what its called, but it is used for electronics work, the solder just flows when you use this stuff.

[vince @ speck]

Originally Posted by 2N1305

I know it isn't really my place to answer, but I figure Vince will say the resistors in the EQ circuit or around the Mic opamp, especially the ones that go from + and - inputs to ground. Oh wait, they probably are already 1%.

Nevermind what I said. Let the pro answer, I need my schematic!

2N1305, that's what I would recommend too.

These days most resistors are 1% unless otherwise noted. Back in the days when that A&H mixer was made, all resistors were 5% unless otherwise noted.

I breifly scanned your input module schematic and observed, for example, the 6.8K phantom resistors are 2%. Change them to 1% 50ppm.

If you're going to use the mic pre then R1-R6, R12, R13, R16-R18, R20 should be 1%.

Unless I'm missing something, it looks like all summing amp and outputs are unbalanced so you don't really need to worry about resistors in the master section.

[The Convicted]

Im almost done with the mixer, but Im starting to have some radical thoughts......... My next project Im building a case, a outboard power supply for my Quantum Audio Labs channel strips(I have 6 of them). I might Cut up my System 8 board and keep 8 channels and sell the the other eight in a side car type mixer with an outboard power supply.
I wonder if some one would be intrested in picking up the other 8 channels?
I know people have mixed reviews on this mixer, but I used to have a Mackie VLZ pro mixer, a number of preamps, and it hasnt been until now that I was happy with the sound of what I am tracking.
I think an 8 channel side car would be a hell of a front end for a Digi 003 setup or similar.
What do U guys think?

Also what could I do with the master and buss sections?

[Pchicago]

Hey..you're inspiring me to do mine..one problem..I have decent soldering but almost no understanding of the electronic concepts behind all of this.

I've installed all new faders in my System 8 Mark One 16/8.

Flushed all the pots from the backside (flipped the board, took off the back, leveled the board and flushed the pots three times over several weeks)

..seems the only way is from the backside with these sealed pots..almost completely resurrected some seriously scratchy pots..still some scratches but they function decently.

Im eyeballing a recap but I get a bit lost and overwhelmed by all the buss wires etc.

Hmm...

Wondering if your board shares the same values in Caps and resistors as mine..

Like I said, you're inspiring me..what an excellent thread.

[The Convicted]

Thanx Bud,

Im actually done with the board, but Ive been working 65-70 hours a week, and havent been able to finish up the last couple of buss wires.
Some of the buss wires Im going to remove again and reinstall because I got tired and started to rush. Its actually not difficult, but tedious work. If you start to feel like rushing, stop and work on it the next day.
As far as the buss wires are concerned take lots of pictures, grab a some sharpie pens in different colors and a straight edge and follow all the buss wires with the pens onto the pcb boards. Try to stay fresh. The longer you let it drag on, the more prone you are to forgeting things.
No with all this said, when I finally power up this beast.........
I HOPE IT DOESNT EXPLODE!!!!!!!!!!!!!!!
Ill be very dfegad

[The Convicted]

Oh Plus I have no electronics knowledge, other than Frankensteining my guitars!

[2N1305]

Originally Posted by The Convicted

I HOPE IT DOESNT EXPLODE!!!!!!!!!!!!!!!
Ill be very dfegad

Which is what will happen if even one of those caps is backwards. I don't want to burst your bubble (besides, I think you already knew) but double check to see if the positive goes to the positive rail side for each capacitor.

Use your multimeter on continuity to make sure...

Good work by the way, taking on a challenge like this.thumbsup

[The Convicted]

Just Powered up the board.............NO eXPLOSION!

[The Convicted]

Heres some more pics of the mixer after rebuild, Check out all the wima caps on channel 1-6.
I am having some issues with it still, but all the channels are working, but when I push the the channel hard with a loud sound there is this harsh sound that peaks the the channel.........I just ordered new caps for the power supply to see if this will help. The Main VU meters are not working now and the # 2 VU meter is pegged, I think that was always like that though.

[2N1305]

Originally Posted by The Convicted

Heres some more pics of the mixer after rebuild, Check out all the wima caps on channel 1-6.
I am having some issues with it still, but all the channels are working, but when I push the the channel hard with a loud sound there is this harsh sound that peaks the the channel.........

Well, that's normal, the opamp is clipping! Turn the gain pot down untl the overload LED doesn't light on the loud peaks.

Nice pictures Check out mine if you like: YouTube - Allen&Heath system 8 mkIII inside

I don't really know why the VU meters don'T work anymore, unless if has to do with PFL button. I simply don't understand the concept of PFL.

cheers

2N

[The Convicted]

Cool Video @ least you have the MKIII thats the nice grey color, Mine is that nasty S**T Brown. Well Im working on the sheet metal part to house my Quantum Channel Strips (I have 6) now, once I get these recapped, I might also Have Jim Williams do his magic to 2 of the strips + an EQ mod (if I can Swing the Money for it). Im going to pick up a power supply from Five Fish to power the Project. Once I get those done, Ill probubly rape the system 8 board of six channels and sell off the rest of the board.
When I finally get into Analog Summing, I want to pick up the Black Lion Audio PM8 to rum stems out.
Gotta Plan, Just no Funds.
Thanx 2N for all the help

[2N1305]

what do you mean "get into analog summing"?

thanks but I don't get all the hip words of the business, my lingo is technical jargon!

2N

[The Convicted]

Sorry, I do all of my mixing in the box. But I like the seperation that I have gotten between insturments when I ran tracks out and back in, through and EQ or a preamp or something. Black Lion Audio has this cool summing box that Ive had my eyes on since it came out, I like the Idea of running stems in stereo pairs out and back in.
Im no pro, and the lingo Ive pick up by other sluts>.........

[2N1305]

aohh,, OK ok. I see now. People use analog processing to spice up their digital recordings. Makes sense. I tend to go the classic "modern route" Analog mixer, analog effects (well ok, some are digital, like reverb) all going into a digital stand-alone multitracker. Say, what do you put your system 8 on? A table? it's gotta be around 70lbs, right?

By the way, you commented on the fact you didn't like the brown colour of the mkII, well, I'll tell ya, if it had 100mm faders, I'd be interested in trading boards. The older for me, the better. Mine still needs recapping, albeit, it does work.

cheers eh!

[The Convicted]

Studio RTA Mix Station and more Desks, Tables & Workstations at GuitarCenter.com.

I have this desk, I took the top tier off it and The system 8 sits on it. It does hang off on both sides, but its sturdy and works for me.