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[johnR]

jetbase wrote on Wed, 20 January 2010 22:12

He used non-polar Arcotronic 105C caps to replace DC blocking caps. Hopefully he might see this thread & mention what he though of them in the Neve. I tried them in my Soundworkshop & felt they weren't really the right thing for this particular console.

In older Neves and others with a single sided power supply, the blocking caps between stages are properly biased with a dc voltage. In newer ones with +/0/- power supplies the blocking caps have nominally zero volts across them and no longer have a proper bias. In practice there is usually a few millivolts across them due to op amp offset, and this would be enough to make switches click and pots crackle without them.

Offset voltage polarity is more or less random, so some of the caps will end up reverse biased. That's why non-polarised electrolytics are chosen, even though they don't sound as good as a properly biased polarised electrolytic.

[Jim Williams]

abtech wrote on Wed, 20 January 2010 13:50

Revealing my ignorance on the subject, I have to ask which (original) chips would be FET vs BiPolar?  Which capacitors could be removed once the "precision" chips were installed?  I realize the damn input module has a zillion chips (several logic chips in addition to the opamps), but how many caps could typically be removed with the chip upgrade or are you only talking bypass caps? Sorry for the long winded question, but this is extremely interesting to me. Thanks, Frank

It depends on the application and design. High impedance inputs and those requiring low bias currents usually favor FET input opamps. Those that require low noise usually benefit from newer bipolar input opamps. Precision bipolars can have the output coupling cap removed if offsets are 2 mv or less. Inputs are dependent on whether input bias current will affect pot wiper noise or switching transients. That is where the FET input devices shine, they have very low input bias current and can usually be directly coupled on their inputs.

Actual selection is done on a case by case study. I usually avoid bipolar caps as their quality is so poor compared to modern tantalum replacement caps like Nichicon HE and Panasonic FM. Even so, all require a quality film cap bypass to avoid the transient damping effects of EL caps.

I am using bipolar caps on some bass amps I designed as some of the players use extended range instruments, some tuned as low as 15 hz. I find THD is reduced at those very low frequencies as the caps are charging so slowly some low frequency waves appear as short term DC reversals. The goal is to obtain .0002% IMD at 20 hz, something I have accomplished.

[maarvold]

ssltech wrote on Mon, 18 January 2010 09:38

Manual sucker??? bugger that!!! Get the Hakko 808. Keith

I asked the guy who mods my gear which desoldering tool to get.  He said "Hakko 808".  I did, then loaned it to him one day and he's had it for 4 months.  I guess he's in love.  He said it is outstanding for completely cleaning out plate-through holes on difficult jobs and he also said thinks that's because the motor's in your hand, not at the end of a hose.  

[ssltech]

He's right... although a complete strip-down and bore-out, replacing EVERY filter, and replacing the  in a benchtop unit is a night-and-day difference, solving a problem which is so gradual that you don't notice it... It's like the boost response on a car which has a lot of piping to and from the intercoolers after the blower... you do notice the 'lag', but you can make it completely disappear by 'pinching' the pipe, if you ever DO need an IMMEDIATE vacuum onset.

Now the hand-tool weight difference between an 808 and a benchtop unit is significant however, so while the 808 scores for being toss-in-the-toolbag friendly, the benchtop unit also pulls a handier vacuum, and can be made to beat even the 808 in terms of instant-on vacuum.

For SERIOUS benchtop work, the older model is still the better of the two, specially for long hours in confined/tight boardpsace, but the 808 is still bloody good!

...and a manual desoldering tool is a torture device by comparison.

Keith

[www.the-terrarium.com]

Thanks for all the great advice, I'm grateful! Chuck I think that is a fantastic idea to do a pair of channels before I get too deep into the process, thanks! A little R&D on this project will no doubt pay off greatly with the end result.

It looks like I am going to go with the Panasonic FM.

I also appreciate the advice of getting the right tool for the job. I am going to go with the Hakko 472D-01 with the pencil tool. I know that is going to save me a tremendous amount of headaches in the process.

The OP amp swap is really interesting. I have swapped 5532's with LT1125's in the EQ and Mic amp section of my 8128. I might explore that as I go through the desk.

Thanks,
Jason Orris

[ssltech]

The  472 will be just perfect. I use the (discontinued) 470, which is largely the same, but has rather different temperature control, and a pistol grip instead of the pencil... looks like the new one is a little better.

I also own a Weller DS900... -MUCH prefer the Hakkos though.

Keith

[Ronzie]

Hey Jason, Chuck alerted me to your under taking and there's some good advice passed onto you so far.  There's some stuff I'd like to add and detract.

The fm's are fine as are the bc/vishay aml 138 (the tan plastic encased versions).  They ALL need to be 105c.  Check your diameters though, it's tight in there. Be sure to get the correct axial/radial positions.  These are know to work and last...

Find a module(if any) that can be a bench mark for the first (2) your going to tackle.

A quick mod you can do to all 11491 eq boards is jumper pin one to pin eight on conn #3.  This gives the eq the correct ground reference and takes the eq out of circuit.  Stock, the eq is always hanging off of the channel (soft switched in or not).  Ughh.

I would recap the audio path ONLY to start. The (2) sandwiched boards (11491 &11492) both need it.  You'll also be taking care of the insert path at the same time.  Be careful unscrewing them.  The stand offs only want to be unscrewed from one side.  If yo decide to pull the eq to do the caps, take care to NOT break the (3) connectors attached to the motherboard.  They're a bitch to get out.  If you leave the eq in the module, again be careful to NOT over flex the connectors.

Depending on the age of the console, how well it was wave soldered and the amount of recaps, take EXTREME care to NOT pull up solder lands.  There have been consoles I've done where it was actually easiest to heat the cap lead and lift it with a small screw driver, then reflow the joint, then suck it out. PIA.  Hopefully you have relatively clean/non cold joints and the Hakko will work like a charm.

There's 20 something caps to change, if you scan the shem, I can show you the ones to replace.  Most likely, the power bypass caps don't need it unless your dist is into the .01%'s.  After pulling the caps, clean the hell out of the solder lands and it's surrounding area.  The impedances running around in there, are very high and you can get stray s**t that messes with logic functions.  Do the same after replacement.

Tantalum caps, believe it or not, have a tendency to add MORE grain to the eq on the VR, the opposite of what your trying to accomplish.  Been there...

There are opamps THAT CAN NOT BE SWAPPED in the VR.  IT WILL OSC....  On the 11491 card, do not change IC3,IC4 or IC6.  Known opamps that work (and sound better) in the eq are the BB/TI opa138 & the BB/TI opa 2138.  Don't blindly start swapping chips as others have recommended.  You'll be sending out signals to aliens and Michelle Bachman.

Get your eq's back to spec and then you should deal with the mic/line card(plenty of mods for that one) on the (2) first modules so you have a clean pair to reference.

The eq boards are childs play. Wait until you get to the mini-fader board. LOL.

Ronzie

[sodderboy]

While in there, why would you not do the decoupling caps?  They are baked and degraded just the same as the audio path caps, and put an extra load on the PSU when they go partial.  For an extra 50 cents or whatever for caps, plus saving the time and stress on the connections, it is a no brainer.
I agree with the separate removal/cleaning steps.  It is a decision made depending on the board and the pump used.  You can pop everything out quickly without putting the iron down and then clean all holes in one step with the pump. It can actually go faster that way.
Mike

[Ronzie]

In theory, the decoupling caps would be a "no brainer".
Not knowing the age,capping history or measurements on Jason's console,it's tough to say.  I no nothing of his budget nor time constraints.  I also no nothing of Jason's capabilities (which I'm sure are fine).

I do know the decouplers don't fail at near the rate of the audio path caps.  It's another 14-16 caps (between the 2 boards) and more chance to create an error on something that MAY not need to be addressed.  Distortion measurements would tell.  So on a VR60, that's around 900 more caps for the eq alone.

This is just my experience and opinion and Jason can take it all with a grain of salt.  It depends on what Jason needs.  Mike could be right for Jason's situation.

After awhile, it's a labor of hate.

Ronzie

[guy_4]

Hi All,

Anybody here with recapping experience of an SSL 4000 E series ?
Cheers,
Guy

[sodderboy]

Same applies.  Tools, skills, documentation, love/hate, etc.
In this case, it is best to start with the PSU's with full examination of all power supply electro-mechanical connections, all caps, fans if noisy etc. then the centre section, then, onto channels.  This is definitely a case where the decoupling are just as important as the audio.  Strangely enough, in my stats, the decoupling caps on the dynamics cards, both sides of the regulators, have the highest failure rate.
The channel job has to be designed around the workings of the studio- do you do one channel at a time as in this VR thread around busy session dates or take it down for 2 days and do some buckets with a crew?
In these trying times, it's best to try to get parts at massive quantity and time to do it when you can.
Mike  

[Ronzie]

guy_4 wrote on Sat, 23 January 2010 17:14

Hi All, Anybody here with recapping experience of an SSL 4000 E series ? Cheers, Guy

LOL... Yep.  I'd hazard a guess Keith(SSLtech) and Mike(sodderboy) do.  I do, but...

Guy, out of deference to Jason, it would be cool to whip up another thread.  I know I'm already confused by Mike's last post.  My braim's what it used to be not.

Ronzie

[guy_4]

Thanks Mike and Ronzie.
I'm helping now the owner of a SSL 4K to recap his console.
The console dates back circa 83/85, and had been stocked for several years
in a barn near the ocean...salted air did a bad job on the boards...
On my advice he bought a tookit and a few thousand Panasonic FM.
Work is in progress now...
Guy

[Phil Nickolay]

guy_4 wrote on Sun, 21 February 2010 09:01

Thanks Mike and Ronzie. I'm helping now the owner of a SSL 4K to recap his console. The console dates back circa 83/85, and had been stocked for several years in a barn near the ocean...salted air did a bad job on the boards... On my advice he bought a tookit and a few thousand Panasonic FM. Work is in progress now... Guy

Hi Guy,
If it's not too late and if you and the owner wanted to, there's a lot that can be done to improve the bottom end frequency response and phase shift while you're re-caping.
Many of the inter-stage coupling caps are just too small, especially on the earlier "E" series consoles.
Phil.

[zmix]

Ronzie wrote on Sun, 24 January 2010 11:20

Guy, out of deference to Jason, it would be cool to whip up another thread. Ronzie

So much for that....