MODS For Soundcraft 400b Input Modules
Old 16th November 2010
  #31
Gear addict
 
The Convicted's Avatar
 

Thread Starter
Im Ordering:
for electrolytics

C1- 100uf / 63v Phantom Blocking Cap (?)
C2- 100uf / 63v Phantom Blocking Cap
C3- 220uf / 10v Line Input
C4- 220uf / 10v Line Input
C7- 1000uf / 10v Mic
C10- 220uf / 35v
C20- 10uf / 50v
C21- 10uf / 50v
C23-220uf / 35v
C24- 1000uf / 25v
C25- 1000uf / 25v
C26- 220uf / 35v

Will I be bypassing all the caps with a wima .1uf?

Last edited by The Convicted; 17th November 2010 at 01:53 AM.. Reason: changed C1 and C2 value
Old 16th November 2010
  #32
Lives for gear
 

Quote:
Originally Posted by The Convicted View Post
Im Ordering:
for electrolytics

C1- 1000uf / 63v
C2- 1000uf / 63v
C3- 220uf / 10v
C4- 220uf / 10v
C7- 1000uf / 10v
C10- 220uf / 35v
C20- 10uf / 50v
C21- 10uf / 50v
C23-220uf / 35v
C24- 1000uf / 25v
C25- 1000uf / 25v
C26- 220uf / 35v

Will I be bypassing all the caps with a wima .1uf?
Take a look at the schematics and only bypass those in the signal path. The power filtering caps don't require bypassing.
Old 17th November 2010
  #33
100uf is enough for c1 & c2.
Old 17th November 2010
  #34
Gear addict
 
The Convicted's Avatar
 

Thread Starter
I havent ordered them yet, Ill change those out too 100uf on my mouser order.
Thanx

Should I change any other ones to another value?
Old 17th November 2010
  #35
Gear addict
 
The Convicted's Avatar
 

Thread Starter
As far as I can see,
Looks like C1,C2,C3,C4, and C7 are the ones needing the .1uf wima cap.

Im I missing something?
Old 17th November 2010
  #36
Gear addict
 
The Convicted's Avatar
 

Thread Starter
For 8 Channels -

ELECTROLYTICS
1000uf / 25v Panasonic FM 667-667-EEU-FM1E102 16 Qty

10uf / 50v Panasonic FC 667-EEU-FC1H100L 16 Qty

1000uf / 10v Panasonic FM 667-EEU-FM1A102L 8 Qty

220uf / 10v Panasonic FM 667-EEU-FM1A221 16 Qty

220uf / 35v Panasonic FM 667-EEU-FM1V221 24 Qty

100uf / 63v Panasonic FC 667-EEU-FC1J101L 16 Qty

POLYPROPOLYENE CAPS

.047uf / 250v WIMA 505-MKP20.047/250/5 16 Qty

3300pf / 400v WIMA 505-MKP23300/400/5 16 Qty

1500pf / 400v WIMA 505-MKP21500/400/5 8 Qty

6800pf / 400v WIMA 505-MKP26800/400/5 8 Qty

.015uf / 630v WIMA 505-MKP4.015/630/10 8 Qty

.22uf / 250v WIMA 505-MKP4.22/250/5 8 Qty

.1uf / 250v WIMA 505-MKP20.1/250/5 64 Qty (For Bypass)

OPAMPS

AD8512BRZ-ND ANALOG DEVICES AD8512BRZ-ND 8 Qty (IC-1)

SO8 to 8 pin dip adapter SO8 to 8-pin DIP Adapter (p/n 970601A) 8Qty

Ordered Tonight
Old 17th November 2010
  #37
Lives for gear
 

Make sure the bypass caps do actually fit in there. MKP4 can be pretty big.
Old 17th November 2010
  #38
Gear addict
 
The Convicted's Avatar
 

Thread Starter
Yea and expensive!
Old 17th November 2010
  #39
Gear addict
 
The Convicted's Avatar
 

Thread Starter
Old 27th November 2010
  #40
Gear addict
 
The Convicted's Avatar
 

Thread Starter
Pics of My Progress

Electros, Wimas, and Bypassing. Plus the ICs with adapters.
Attached Thumbnails
MODS For Soundcraft 400b Input Modules-147.jpg  
Old 28th November 2010
  #41
Gear addict
 
The Convicted's Avatar
 

Thread Starter
more
Attached Thumbnails
MODS For Soundcraft 400b Input Modules-140.jpg  
Old 28th November 2010
  #42
Gear addict
 
The Convicted's Avatar
 

Thread Starter
more
Attached Thumbnails
MODS For Soundcraft 400b Input Modules-141.jpg  
Old 28th November 2010
  #43
Lives for gear
 

I think it would be a good idea to install sockets for the ICs.
Old 28th November 2010
  #44
Gear addict
 
The Convicted's Avatar
 

Thread Starter
Your Right, I didnt think of that.
Old 20th December 2010
  #45
Gear addict
 
The Convicted's Avatar
 

Thread Starter
anyone know how I can add phantom power to these?
Old 9th February 2011
  #46
Gear addict
 
The Convicted's Avatar
 

Thread Starter
Ive gone about as far as I can go with these, and Im going to take them to a tech to sort out some issues but here are some pics of the updated project
Attached Thumbnails
MODS For Soundcraft 400b Input Modules-dscn1343.jpg   MODS For Soundcraft 400b Input Modules-dscn1346.jpg   MODS For Soundcraft 400b Input Modules-dscn1347.jpg   MODS For Soundcraft 400b Input Modules-dscn1344.jpg  
Old 9th February 2011
  #47
Lives for gear
 

48volt power supply can you post the schematic? if you add sockets make sure they are milled
Old 9th February 2011
  #48
When I redo a 200B, I remove all the electrolytic caps except in the mic preamp. There are none left from line in to stereo mix outputs. That requires low offset precision opamps and a scope really helps to detect instabilities.

Best cap I ever heard was a piece of wire.
Old 9th February 2011
  #49
Lives for gear
 

Quote:
Originally Posted by Jim Williams View Post
When I redo a 200B, I remove all the electrolytic caps except in the mic preamp. There are none left from line in to stereo mix outputs. That requires low offset precision opamps and a scope really helps to detect instabilities.

Best cap I ever heard was a piece of wire.
Jim, just a few days ago I removed a few caps from the channels in my 200B and found it worked and sounded quite a bit better. So can I remove the caps at the line input, the input amplification pot and the ones in the master section as well? I've used low-DC op amps (AD8510/12, OPA1611, OPA827) biased into Class a with a resistor throughout the console. I think in the position at the input pot someone reported an oscillation problem with very big caps, so no cap at all should be even worse. Also, the ones at the line input seem to be there to protect the input transistors, long before the signal goes through one of the op amps. I guess it can be removed as long as I don't connect stuff like phantom power to the line inputs accidentally?

I'd really like to remove all these caps, since - even with very good bypass caps - there is still sonic degradation from the caps in the signal path...
Old 9th February 2011
  #50
Gear addict
 
The Convicted's Avatar
 

Thread Starter
we have a 2 channel tektronix 2205 scope here at the shop, b ut I have no idea how to use it or where to hook it up.

I dont know really what issues Im facing with each strip. In the first 2 channels I used AD8512 in all 4 positions on dog brown headers but they are soldered to the board so I cant remove them . On the other 2 channels I used the AD8512 in the preamp, and the Last position I kept the TL071s in the preamp section for now.

I belive I did the outputs as Jim suggested properly, but I was gettin very low out put volume when I briefly checked.

If you guys could offer some advice on how to use these scope, Id appreciate it.
Old 9th February 2011
  #51
Lives for gear
 

Quote:
Originally Posted by The Convicted View Post
we have a 2 channel tektronix 2205 scope here at the shop, b ut I have no idea how to use it or where to hook it up.

I dont know really what issues Im facing with each strip. In the first 2 channels I used AD8512 in all 4 positions on dog brown headers but they are soldered to the board so I cant remove them . On the other 2 channels I used the AD8512 in the preamp, and the Last position I kept the TL071s in the preamp section for now.

I belive I did the outputs as Jim suggested properly, but I was gettin very low out put volume when I briefly checked.

If you guys could offer some advice on how to use these scope, Id appreciate it.
Do you have the same problem an all channels? If not, it's somewhat likely you accidentally lifted a trace. It happened quite a lot with my 200B even using a good desoldering station. They're not the most sturdy of PCBs...

To find out where the problem lies send a sinewave through and just trace it with the scope. The problem is where your signal dissapears.
Old 9th February 2011
  #52
Gear addict
 
The Convicted's Avatar
 

Thread Starter
cool, our electrician just showed up, he said he'd help me out at the end of the day.
Old 9th February 2011
  #53
Gear addict
 
The Convicted's Avatar
 

Thread Starter
Quote:
Originally Posted by doulos30 View Post
48volt power supply can you post the schematic? if you add sockets make sure they are milled
My fist post has the scematics in pdf.....I still havent figured out where to apply the 48 v to on the module
Old 10th February 2011
  #54
Lives for gear
 

Did it - removed them all (in the channel). Sounds great, less wool and grime! Oscillation starts at the highest amplification, but I never use that anyway and I've got better transistors coming that might react differently anyway.

Thanks Jim!
Old 11th February 2011
  #55
Moderator
 
Tim Farrant's Avatar
 

Quote:
Originally Posted by Jim Williams View Post
Best cap I ever heard was a piece of wire.

Hahahahahahahahaha!!!!
Old 11th February 2011
  #56
Gear addict
 
The Convicted's Avatar
 

Thread Starter
All the channels seem to have the same problem......Extremely Low output. I didnt have a tone generator so I used my IPOD for signal. I traced the signal through the Line input, IC 1 thru 3 seem too work fine. When I got to Resistor 34, it reduced the signal to a minmal level. I couldnt get transistor 3 and 4 to trigger a signal, which is funny because the Red LED lit up when the signal clipped. IC 4, which I changed out a AD8510 I couldnt trigger a signal.
I plugged in a stock 400b strip and ran signal thru it and it seemed to have the same issues with lowoutput. I didnt run a scope over it though.
I think its time for a tech to look at this...........
Old 11th February 2011
  #57
Lives for gear
 

Quote:
Originally Posted by The Convicted View Post
All the channels seem to have the same problem......Extremely Low output. I didnt have a tone generator so I used my IPOD for signal. I traced the signal through the Line input, IC 1 thru 3 seem too work fine. When I got to Resistor 34, it reduced the signal to a minmal level. I couldnt get transistor 3 and 4 to trigger a signal, which is funny because the Red LED lit up when the signal clipped. IC 4, which I changed out a AD8510 I couldnt trigger a signal.
I plugged in a stock 400b strip and ran signal thru it and it seemed to have the same issues with lowoutput. I didnt run a scope over it though.
I think its time for a tech to look at this...........
Haven't got the schematics, so I can't say anything specific. But this sounds like the outputs are wired the wrong way, since you say it's the same with the stock channels.
Old 27th February 2011
  #58
Lives for gear
 

Quote:
Originally Posted by Jim Williams View Post
When I redo a 200B, I remove all the electrolytic caps except in the mic preamp. There are none left from line in to stereo mix outputs. That requires low offset precision opamps and a scope really helps to detect instabilities.

Best cap I ever heard was a piece of wire.
Jim, how do you deal with the cap at the input gain pot? With this one removed only half the gain is useable, after that DC seems to overload the transistor.
Old 27th February 2011
  #59
Yes it will due to transistor mismatch. You will need to use that cap. I place a 1000 uf 10v panasonic FM there.

Also keep in mind any work you do that messes it up will be charged back to you for repairs.
Old 27th February 2011
  #60
Lives for gear
 

Quote:
Originally Posted by Jim Williams View Post
Yes it will due to transistor mismatch. You will need to use that cap. I place a 1000 uf 10v panasonic FM there.

Also keep in mind any work you do that messes it up will be charged back to you for repairs.
Thanks Jim. I replaced the transistors with 2N1085, matched them all for hFE as closely as possible, but some are not as well matched as they should, and this seems indeed to relate to difference in maximum gain before breakup for the channels. Will have to test it some more. Panasonic FM 1000 uf 10V was what I had in there before (with added bypass caps), but there is a very audible difference, it just sounds way better without any cap.
New Reply Submit Thread to Facebook Facebook  Submit Thread to Twitter Twitter  Submit Thread to LinkedIn LinkedIn  Submit Thread to Google+ Google+ 
 
Thread Tools
Search this Thread
Search this Thread:

Advanced Search
Similar Threads
Thread
Thread Starter / Forum
Replies
drybones / Gearslutz Secondhand Gear Classifieds
0
CharlesCola / Gearslutz Secondhand Gear Classifieds
12
drastic / Gearslutz Secondhand Gear Classifieds
3
zurich / Gearslutz Secondhand Gear Classifieds
1
Mike Derrick / Gearslutz Secondhand Gear Classifieds
0

Forum Jump
 
Register FAQ Search Today's Posts Mark Forums Read

SEO by vBSEO ©2011, Crawlability, Inc.