Allen And Heath system 8 MK II RECAP Project

[The Convicted]

Heres some pics of the power supply before and after
there was a leaky cap on the Power Supply

[The Convicted]

Heres all the used caps, excluding the ones on the floor!

[The Convicted]

Now, I thought that I fixed the problem with the VU meters. When I went to double check all joints and buss wires, I forgot to continue to solder the L R main buss bars on the Buss section. After I soldered that, I checked all wires from the VU meters and they were ok. When I fired up the mixer the pegged #2 meter slowly made its way back to the left. Everything looked good. I took it to the studio and................That #2 VU meter is pegged again!
Oh well Ill have to live with it!

[The Convicted]

Oh and the Main VU meters work in PFL mode.

[The Convicted]

So here now is the complete list of all the caps that I bought.
From Digikey:
P10321-ND 47uf/50v Elect FC Radial Cap- Panasonic FC

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

P12923-ND 47uf/25v FM Radial Cap -Panasonic FM

P12924-ND 100uf/25v FM Radial Cap -Panasonic FM

P910-ND 10uf/16v KG Radial Cap - I couldnt find the FC or FM on this one, but its a panasonic KG series

These are all the Electrolytics shared on the Input channels, Buss, and Master.

These are all the Polyester and Polypropolyne Caps I used to replace all the ceramics (I ONLY DID 6 Channels Like This)

From Mouser Catalog:

1500pf / 100v Wima Cap 505-FKS31500/100/10P
3300pf / 100v Wima Cap (3N3) 505-FKS23300/100/10
330pf / 100v Wima Cap 505-FKP2330/100/5
220pf / 100v Wima Cap 505-FKP2220/100/10
.0039uf / 100v Nichicon Cap 647-QYX2A392KTP (This One Substitutes .04/100v cap)

Power Supply Caps From Mouser Catalog:

470uf / 40v Vishay Cap 594-2222-138-17471 (2QTY)
2200uf / 40v Vishay Cap 594-2222-138-17222 (2QTY)
2200uf / 50v Nichicon Cap 647-TVX1H222MCD (3QTY)

[The Convicted]

Ill Post Some Sound Files Once I get the chance to record again.
Hope this Helps you guys looking to service your own System 8 MKII!

[2N1305]

Very nice work, well documented, I like! Maybe I'll take your list whenever I do mine! lordy, I still need a table to put it on... Then a chair!

[do-ob]

Thanks for posting this! Really inspired me to do mine.

Just a quick question, like you I've been eyeing the new BLA summing box, but would be interested to see if the System 8 would be able to fulfill this function instead (at a similar quality...)

Does anyone have any thoughts on this?

[The Convicted]

BLA is sending my sig mod AI3 back to me. It should arrive on Monday. Once I get it back, I am going to explore mixing and summing on the board.
Ill let you know how it goes!

[The Convicted]

Got my Ai3 back from BLA.........Hook it up, sounds great. But the adat port on my Digi 003 is busted, retaining clip is broken and wont lock a cable in it. Another $150 to dump

[The Convicted]

I just wanted to add...............

Ive been doing some tracking lately, all I have at his moment is the system 8 for mic preamps, they stack very nicely together while mixing.
I dont know if Im just crazy but i was un able to get this untill I started using this console.
Tracking through just outboard preamps, just never cut it for me. I also dont have anymore annoying cymbal harshness bleeding into the drum tracks anymore either.
I know people advise against this, but I love tracking with eq-
Kick -RE-20-60hz +2to 4db.....400hz cut 4 to 8db......6k shelf +2 to 3 db

Toms-hightom E835-low tom D-112- 120hz +3 to 4db.........400hz cut 4 to 8db.......6k shelf +2 to 3db

Snare-MD421- 120hz cut 3 to 4db..........3k +3 to 4db.........6k shelf +2 to 3db

OH-Joly modded ultimate Nady CM-90's- 800hz +2db......12k shelf +2 to 3db

I do the some more moderate eqing and compressing in the box once all the insturments are tracked.
Ill be posting a song very soon completely tracked on the system 8....Just have to track my guitar parts on it and figure out some background vocal arrangements and we're done.
Keep Watch!

[The Convicted]

I know I stated this before, but

I am most likely, going to rape this mixer of 4 to 8 channels to use as a frontend for my system.

with the remainder of the channels, I will build a small extension type mixer out of aluminum, and also add in the power supply.
Anyone intrested?

The rest of the mixer Ill part out.

I dont really have a need for a full console, + could use the space.

[JohnnyDMonic]

Hey there,

I stumbled across this thread the other day. I have 2 System 8s - a 16-4 and a 16-8. They're both Mk1's, no EQ cut switches and only 90mm faders. Both of them work pretty much, but they both also have various (different) problems.

What I'm planning is to take all of the channel strips out of the 16-4 (which I see as the less useful one of the two due to it having only 4 group busses), re-capping them and then fitting them into the 16-8. I'd also like to put 1% metal film resistors in the places that matter, and maybe add the EQ cut switches too (seeing as I have 16 spare channel strips with all the buttons, etc..)

Firstly, thanks for sharing your re-capping story. It's pushed me from the "hmm I might do that one day" stage to "right, i'm off to buy all the bits" stage! I've printed off all the schematics and worked out the bits I'd like to change, etc..

I'd also like to ask a couple of questions, if you don't mind?

You said this after you re-capped yours:

Originally Posted by The Convicted

but when I push the the channel hard with a loud sound there is this harsh sound that peaks the the channel.........

Did you manage to work out why this was?

Also, I was looking at your list of replacement caps and noticed you mention replacing the 0.04uf caps in the LF EQ section with 0.0039uf caps. Is that a typo? did you mean 0.039? I looked up both on Digikey and the Nichicon part no. for 0.039uf cap is QYX2A393KTP.

I'm quite looking forward to doing this project. I love using this desk at the moment but things like the gain pots only working over the last 2% of their range is really annoying! (i turn them up and up.. nothing.. then suddenly - BAM, full gain!) Hopefully this will fix all these kinds of problems.

Does yours have any less background noise after doing these mods? Mine is generally OK for noise until the gain is up really high (which, due to the problem above, is pretty much most of the time!).

Cheers, many thanks,

John.

[The Convicted]

Originally Posted by JohnnyDMonic

Hey there,

I stumbled across this thread the other day. I have 2 System 8s - a 16-4 and a 16-8. They're both Mk1's, no EQ cut switches and only 90mm faders. Both of them work pretty much, but they both also have various (different) problems.

What I'm planning is to take all of the channel strips out of the 16-4 (which I see as the less useful one of the two due to it having only 4 group busses), re-capping them and then fitting them into the 16-8. I'd also like to put 1% metal film resistors in the places that matter, and maybe add the EQ cut switches too (seeing as I have 16 spare channel strips with all the buttons, etc..)

Firstly, thanks for sharing your re-capping story. It's pushed me from the "hmm I might do that one day" stage to "right, i'm off to buy all the bits" stage! I've printed off all the schematics and worked out the bits I'd like to change, etc..

I'd also like to ask a couple of questions, if you don't mind?

You said this after you re-capped yours:

Did you manage to work out why this was?

Also, I was looking at your list of replacement caps and noticed you mention replacing the 0.04uf caps in the LF EQ section with 0.0039uf caps. Is that a typo? did you mean 0.039? I looked up both on Digikey and the Nichicon part no. for 0.039uf cap is QYX2A393KTP.

I'm quite looking forward to doing this project. I love using this desk at the moment but things like the gain pots only working over the last 2% of their range is really annoying! (i turn them up and up.. nothing.. then suddenly - BAM, full gain!) Hopefully this will fix all these kinds of problems.

Does yours have any less background noise after doing these mods? Mine is generally OK for noise until the gain is up really high (which, due to the problem above, is pretty much most of the time!).

Cheers, many thanks,

John.

Hey John,
your welcome. As far as pushing the channel hard, I just turned down the gain. The .004 cap was a recommedation in case the .0039 was not available. There was some scratchuness in the pots before I recapped, but seem like they all work well now. I would go with Vinces post about the resistors, I didnt do it but his info was great.
The noise went away in mine after I recapped the power supply, I had a leaky cap in the phantom circuit. Its as quiet as It can be, still abit hissy, but sounds great. The wima caps in channel 1-6 cleared up the sound alot. The EQ benifited greatly. Use Polypropolyne Caps.

[The Convicted]

I promised I would post something, just got done tracking guitars tonight.
All Drums were done with the system .
Kick - RE20
Snare- MD421
Tom 1- Beta 57
Tom 2- D112
OH- Pair of Oktavamod CM90's (Ultimate 603 mod)
2 samples running underneath the kick
and 1 sample underneath the snare.
Drum Buss Compression - Stock Pro VLA II

Bass- Direct Box into a Black Lion Audio Autuer
Rhythm Guitar (right panned) - MD421 - BLA Autuer

All other Guitars Recorded with the Quantum Audio Labs Strips

The song is yet to be finished, vocals need to be recorded. And Mixed
This my nephews band- They are 15 to 16 year old kids!

I Love the Quantums!

[The Convicted]

The Board is now out of my studio, and for learning purposes, Im going to tear it apart again, fix some issues and modify the channels.
I want to change out the ICs on at least on the mic pre. I might go with an AD8512 to replace the Tl072.
If any one has any suggestions about raising cap values and IC replacement, Im all ears!

Im also going to cut the bussbarrs and add a molex connector for ease of servicing.

[2N1305]

Originally Posted by The Convicted

Im also going to cut the bussbarrs and add a molex connector for ease of servicing.

Remember that you have TWO sides of each to connect... There aren't many connectors that allow you two daisy chain themselves. Unless I'm missing something...

[The Convicted]

Originally Posted by 2N1305

Remember that you have TWO sides of each to connect... There aren't many connectors that allow you two daisy chain themselves. Unless I'm missing something...

I found a 16 pin header for the bussing, + a 2 pin header for LR, I need to look at it again.

[rekloos]

you guys had any issues with the plastic knobs? like the top [the colored or brown] coming off?
keeps happening to me and tried couple different glues but to no avail.....
maybe i should just get new ones....

[The Convicted]

I havent had any issues, but finding the knobs may be hard.

[The Convicted]

Originally Posted by vince @ speck

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.

This is the first thing Im going to do.
I found all the metal film resistors @ mouser except for the 1.8k.
Im looking at the vishay/dale resistors, they are kind of pricey
Could I go xicons or koa speers? or stick with the Vishays?
Also any recomendations on transistors?

[rekloos]

Originally Posted by The Convicted

Heres some pics of the power supply before and after
there was a leaky cap on the Power Supply

I was wondering why u choose to mess with the power supply at all as it seems that other ppl including Jim Williams say you should get a newer power supply?

[The Convicted]

Originally Posted by rekloos

I was wondering why u choose to mess with the power supply at all as it seems that other ppl including Jim Williams say you should get a newer power supply?

Because I wasnt doing really any mods to the board, until now. And even with what Im doing, I will most likely do a few channels with IC 1-3 with AD8512 's , which seems to be a good replacement for the TL072.

Im not going overboard with mods. And after Im done Im going to sell the board.

[rekloos]

Originally Posted by The Convicted

Because I wasnt doing really any mods to the board, until now. And even with what Im doing, I will most likely do a few channels with IC 1-3 with AD8512 's , which seems to be a good replacement for the TL072.

Im not going overboard with mods. And after Im done Im going to sell the board.

k, cool.....
i think i'm gonna replace mine soon as it seems that's the first thing to do and eventually start modding/replacing other things as my board needs a lot of attention.
i have the 24ch version and i'm still trying to decide if i should just try to find another one that's in better shape then mine and wont have to mess with it or start replacing parts on mine......i kinda also feel a bit nostalgic about this board and although it's not in the greatest shape internally and externally i'm not that concerned, just want the same board but up to date and get rid of all the scratchy pots/buttons/faders.

lemme know what u have left to part with, i might b interested in some....

[1rjchris]

Could not find an SR thread so thought I would post here. Hope no one minds.
I am trying to find replacement faders for my MKI series console. Listed as TDM 90mm 5k. Mouser was no help. Alps corporate not much better. Sent email to A&H england and have gotten no reply. I really want to save this console as we have done some extensive modifications and it sounds great, but I have some some totally dead channels due to faders.
Any help greatly appreciated.
Robert

[2N1305]

Robert, I think your best bet is to find a used one for parts...

but in case you want to go the "new" way, here are some other manufacturers:

-Song Huei (Taiwan potentiometer manufacturer)
-Omeg
-Noble

Can you not adapt something else to work, I mean as long as the screw locations are the same, right?

2N1305

[The Convicted]

Originally Posted by 1rjchris

Could not find an SR thread so thought I would post here. Hope no one minds.
I am trying to find replacement faders for my MKI series console. Listed as TDM 90mm 5k. Mouser was no help. Alps corporate not much better. Sent email to A&H england and have gotten no reply. I really want to save this console as we have done some extensive modifications and it sounds great, but I have some some totally dead channels due to faders.
Any help greatly appreciated.
Robert

what kind of mods are done to you MKI

[The Convicted]

Looking for a Transistor Upgrade.....Anyone know what would work?

[oscillat0r]

Originally Posted by The Convicted

I found a 16 pin header for the bussing, + a 2 pin header for LR, I need to look at it again.

Let me know if you try this and how it goes for you. I was considering whether I could even wire up a connector on each channel and then use ribbon cables.

I've been searching for examples of people replacing buss wire with alternate connectors but no luck yet. To me this is the biggest PITA on the mixer and making it easier to remove, modify, and reattach individual channels would be huuuuge.

[The Convicted]

I have a good idea what to do.
If you replace the buss barr with a wire and then into a molex connector( the connector will not have the same spread as the channel). Ill pick up a molex connector and try it