C33 Update Project 2013

[Gregory]

Hi Greg, if you want to do a perfect job desolder everything ( screw and washer ) and use strong abrasive paper and everything will look like new, then resolder and you will see that it will be nicer than original.... :thmbsp:

Ok.. got that! sounds like a plan!


-Gregory

 

[Gregory]

Rethinking new caps

About to get back inside the C33 and would like to think over which replacement CAPS to install. In short, I didn't install any Nich KZ (will check to make sure) because the 10uF KZ only comes in 100V rating. This is OVERKILL for an interstage coupling cap that has a 2.5 VAC signal on it, and 0 VDC on the nearby IC pins. Besides that.. the leads are 0.031" Dia and the boards will need opening up.


Loudness PCB for instance

INPUTS: Below is a marked-up photo of the LOUDNESS PCB. The rectangular INPUT caps are 0.47 uF metalized polyester. Could they be replaces with 10uF Muse ES non-polarized? Would it make any difference? is it even necessary?

OUTPUTS: Had planned to use Nich FG (Fine Gold) caps there, but am on the fence about Nich KZ. Put in 47uF, 50V KZ's? They're awfully big and the leads are heavy... especially to replace the original 16V electrolytic. What about using Nich ES non-polarized? There's no DC across those caps and ES are physically smaller?

SUPPLY RAILS: The original 1uF, 50v are small.. and the Nich Fine Gold are even smaller. Are high-grade KZ necessary for the Power Supply and supply rails? I'm thinking of removing the two FG's installed for C1311-12 and using KZ's. Use ALL KZ's? Is there any REAL improvement over FG's?


C33 Compandor board with Voltage Rail caps, Input caps and Output (Signal Path) caps pointed out.


Here's the schematic of the LOUDNESS circuit for reference..




So.. the big KZ caps with their HIGH voltage ratings and heavy leads don't seem to be the appropriate choice. Or are they?


-Greg

 

[jlovda]

Rethinking new caps

About to get back inside the C33 and would like to think over which replacement CAPS to install. In short, I didn't install any Nich KZ (will check to make sure) because the 10uF KZ only comes in 100V rating. This is OVERKILL for an interstage coupling cap that has a 2.5 VAC signal on it, and 0 VDC on the nearby IC pins. Besides that.. the leads are 0.031" dia and the boards will need opening up.


Compandor PCB for instance

INPUTS: Below is a marked-up photo of the COMPANDOR PCB. The rectangular INPUT caps are 0.47 uF metalized polyester. Could they be replaces with 10uF Muse ES non-polarized? Would it make any difference? is it even necessary?

OUTPUTS: Had planned to use Nich FG (Fine Gold) caps there, but am on the fence about Nich KZ. Put in 47uF, 50V KZ's? They're awfully big and the leads are heavy... especially to replace the original 16V electrolytic. What about using Nich ES non-polarized? There's no DC across those caps and ES are physically smaller?

SUPPLY RAILS: The original 1uF, 50v are small.. and the Nich Fine Gold are even smaller. Are high-grade KZ necessary for the Power Supply and supply rails? I'm thinking of removing the two FG's installed for C1311-12 and using KZ's. Use ALL KZ's? Is there any REAL improvement over FG's?

C33 Compandor board with Voltage Rail caps, Input caps and Output (Signal Path) caps pointed out.


So.. the big KZ caps with their HIGH voltage ratings and heavy leads don't seem to be the appropriate choice. Or are they?


-Gregory

If you got a unit back from Terry Dewick that was recapped, it would be loaded with green caps (Muse ES Bipolar). You seem to be inferring that FG caps are subpar.

 

[Gregory]

If you got a unit back from Terry Dewick that was recapped, it would be loaded with green caps (Muse ES Bipolar). You seem to be inferring that FG caps are subpar.

Nichicon KZ chart

I'm implying that Muse KZ are NOT small-signal caps. See the KZ chart below with three voltage ratings and typically larger cap values.




Nichicon FG chart

The FG chart follows with smaller values and a bigger variety. Voltages go down to 6.3 Volts.


The smallest FG values for both 50V and 100V are still only 5 x 11 mm in size, That's tiny, and the leads are thin!


Nichicon ES chart

Voltage ratings for ES caps also go down to 6.3 Volts.


The smallest FG values for both 50V and 100V are still only 5 x 11 mm in size, That's tiny, and the leads are thin!


I think putting in a 100 VDC KZ with heavy leads as a signal-path cap where there is basically 0 volts DC and typically 2.5V audio isn't the best choice. Also I think a Fine Gold (FG) will sound very good for coupling, as do the ES non-polar. The KZ type can go in the power supply ok?


Replace MPE with ES?

Thinking of getting adventurous and replacing the rectangular stock MPE (metalized poly) coupling caps on the COMPANDOR board with green Muse ES, mainly for consistency with other preamp sections. The value could be bumped-up from 0.47 to 1uF for a bit extra 'uumph.' The MPEs could always be put back in. I like what I'm hearing with the green ES and FG caps so far. :yes:


EDIT: have dropped the idea of replacing the MPEs which are 5% tolerance.


-Greg

 

[jlovda]

Wow! That is some analysis. Can your wife put up with a perfectionist engineer?

I own two C34V preamps and recapped both, one about four years ago and the other about eighteen months ago. On both of these units I used a combination of Nichicon Muse ES BP, Nichicon FG, Panasonic BP and Elna Simic. I used more Muse ES parts in the second project. I used larger Nichicon electrolytic caps (about 6000 uf) for the two filter caps. Diameter is critical for these two caps. Of course for all the caps I chose parts with close diameter and length sizes. The Panasonics were used for the power supply inputs on each circuit board. I also changed about six or eight of the the National low noise Op Amps. I changed the four rectifier diodes to high speed glass Vishey types. I also changed the two audio shunting FETs used to silence turn-on noise in the monitor amp. I tried to use exactly the same voltage ratings and values for the audio path caps but some were up to 50% higher in capacity. None of the caps were rated at higher than 50 v. I used the values in the service manual as a guide. The only place I had to drill out larger holes was for the power supply capacitors. I used snap-in caps with large, short, stiff leads. they were easy to straighten horizontally and rebend to the correct spacing. I was recommended to me to change the small LDRs on the monitor amp board to equilize the gain. It really helped on my 2125 using Excelitas VTL5C9 parts but the small Clairex parts on the C34V monitor amp are no longer available and gone even with a Google search.

Maybe it was just intuition but I assumed these caps were much better than the OEMs Mac put in the units. Ron-C mentioned that Mac used audio grade Rubicon. The only difference now is the additional spec of low ESR (value?).

The units sound great and I am very happy with the results. It took about a week off and on for each unit, removing flux from each solder joint being the most time consuming part. The trickiest part was removing old caps that had their leads folded right onto the solder pad. An X-Acto knife was required to get under the wire and rotate it up. These caps were mostly in the phono section inside the shielding box.

I am working on the meters of my 2125 now. To take its place I am using the monitor amp of one of the C34V. I am surprised at how good 20 wpc sounds with my pair of KLH model Fives at medium levels.

Good luck with your project.

 

[Bubo]

I own two C34V preamps and recapped both, one about four years ago and the other about eighteen months ago. On both of these units I used a combination of Nichicon Muse ES BP, Nichicon FG, Panasonic BP and Elna Simic. I used more Muse ES parts in the second project. I used larger Nichicon electrolytic caps (about 6000 uf) for the two filter caps. Diameter is critical for these two caps. Of course for all the caps I chose parts with close diameter and length sizes. The Panasonics were used for the power supply inputs on each circuit board. I also changed about six or eight of the the National low noise Op Amps. I changed the four rectifier diodes to high speed glass Vishey types. I also changed the two audio shunting FETs used to silence turn-on noise in the monitor amp. I tried to use exactly the same voltage ratings and values for the audio path caps but some were up to 50% higher in capacity. None of the caps were rated at higher than 50 v. I used the values in the service manual as a guide. The only place I had to drill out larger holes was for the power supply capacitors. I used snap-in caps with large, short, stiff leads. they were easy to straighten horizontally and rebend to the correct spacing. I was recommended to me to change the small LDRs on the monitor amp board to equilize the gain. It really helped on my 2125 using Excelitas VTL5C9 parts but the small Clairex parts on the C34V monitor amp are no longer available and gone even with a Google search.

Maybe it was just intuition but I assumed these caps were much better than the OEMs Mac put in the units. Ron-C mentioned that Mac used audio grade Rubicon. The only difference now is the additional spec of low ESR (value?).


.

John,

I'm a little new to the cap selection process, if you had identical spec ES and FG caps what would make you take one over the other?

I'm looking at recapping (with some help) a fairly straight forward Yamaha amp that is all Nichicon and has exactly one ES cap.

If I could do everything in FG and the high temp KA caps why not?

http://www.nichicon-us.com/english/products/alm_mini/pict_f.htm

Thanks,

Mark

 

[jlovda]

John,

I'm a little new to the cap selection process, if you had identical spec ES and FG caps what would make you take one over the other?

I'm looking at recapping (with some help) a fairly straight forward Yamaha amp that is all Nichicon and has exactly one ES cap.

If I could do everything in FG and the high temp KA caps why not?

http://www.nichicon-us.com/english/products/alm_mini/pict_f.htm

Thanks,

Mark

I guess I figure ES and FG to be about equivalent (my unscientific opinion) except that ES caps are a little bit bigger. Also, you don't have to worry about putting the ES caps in backwards. As noted above Terry Dewick uses a lot of them and they sound OK to me. If you asked me why some capacitors went here and others there I couldn't answer unless the schematic specifically called out BP. I did keep both channels identical. I'm not familiar with KA.

 

[Bubo]

I guess I figure ES and FG to be about equivalent (my unscientific opinion) except that ES caps are a little bit bigger. Also, you don't have to worry about putting the ES caps in backwards. As noted above Terry Dewick uses a lot of them and they sound OK to me. If you asked me why some capacitors went here and others there I couldn't answer unless the schematic specifically called out BP. I did keep both channels identical. I'm not familiar with KA.

KA is the high temp totl Nichicon in the audio family.

Check the schematic on the one BP, will do.

PCB and caps have N clearly marked, so I wasn't too worried about putting them in backwards.

Thanks!

 

[Gregory]

Wow! That is some analysis. Can your wife put up with a perfectionist engineer?

I own two C34V preamps and recapped both, one about four years ago and the other about eighteen months ago. On both of these units I used a combination of Nichicon Muse ES BP, Nichicon FG, Panasonic BP and Elna Simic. I used more Muse ES parts in the second project. I used larger Nichicon electrolytic caps (about 6000 uf) for the two filter caps. Diameter is critical for these two caps. Of course for all the caps I chose parts with close diameter and length sizes. The Panasonics were used for the power supply inputs on each circuit board. I also changed about six or eight of the the National low noise Op Amps. I changed the four rectifier diodes to high speed glass Vishey types. I also changed the two audio shunting FETs used to silence turn-on noise in the monitor amp. I tried to use exactly the same voltage ratings and values for the audio path caps but some were up to 50% higher in capacity.

Hey thanks, that means a lot coming from someone like you. Tweets is ok with taking gear apart in the kitchen but it wouldn't be kool to rebuild a Ford Mustang engine in there like Tom Cruise does in the movies.

Desoldering and replacing parts inside an amplifier with the intent of making it sound better is so far beyond her comprehension, and she has "never heard anything like" what comes out of the 70s-80s Mc amps.

Terry said once or twice that ES caps have back-to-back aluminum 'lytics inside. I'll probably leave the MPE caps in place unless there's some concurrence. The EQ Summing ICs have two cascaded 0.22uF MPEs in cascade and they are 5% tolerance. The COMPANDOR PCB is the only stage in the entire preamp [from hi-level] that hasn't had signal path 'lytics replaced.. except for the EQ board which is pretty well hidden behind the front panel. I'm not ready to take the glass apart at this time.


I think it will be FG and ES caps going in, and will upgrade the power supply to KZ. You think the rectifier diodes should be replaced? I ordered a bunch of them and wasn't too happy with the specs.


-Greg

 

[Gregory]

if you had identical spec ES and FG caps what would make you take one over the other? If I could do everything in FG and the high temp KA caps why not?

The ES caps are back-to-back electrolytics... I think is what Terry said. Why use high temp? How hot is the circuit going to get? and for how long? You're on the right track studying and posting Nichicon specs. One of the data sheets didn't mention ESR and that seems to be an important parameter.

Another concern about changing out ICs.. how would you know each and every chip meets spec? Wouldn't you need to have test gear to measure distortion after an IC replacement? What's the confidence level here?


-Gregory

 

[Gregory]

It was recommended to me to change the small LDRs on the monitor amp board to equalize the gain. It really helped on my 2125 using Excelitas VTL5C9 parts but the small Clairex parts on the C34V monitor amp are no longer available and gone even with a Google search.

I think you have to be careful, or have a lot of experience and confidence to change many dozens of caps on multiple boards, and change silicon all at once. Ask yourself.. what is the risk in doing this, or doing that? and how can a series of replacements be verified as successful? It's reasonable to separate a major project into stages with tests in between to be sure there are no issues. Might as well spread the enjoyment out over months, even years! :yes:


-Gregory

 

[Bubo]

In no particular order, less quotes:

* I thought the ESR issue had to do with drift over time (30 years)?

* Verifying changes as you go has a lot of appeal for my friend who is back-seating me on this, he is an IC designer (digital engineer). If nothing else it cuts down on the trouble shooting when something isn't quite right.

* My friend is very reluctant to get involved with changing the OP amps without more specs on the originals, on the other hand you can always go backwards if you don't like the results. I'm pretty sure that the headphone amp guys do op amp rolling to play with the sound.

* My recollection for a base design goal was, will be assembled with auto-insertion machine and wave-soldered. Since we are not auto-inserters and I can't afford a wave machine (or much else) perhaps this should be thrown out as a repair goal.

* Within spec, a cap is a cap (or at least this is what my Eng friend and busy repair shop owner keep telling me). I have a Yamaha tuner that IMHO was rebuilt by a genius, he/she used axial electrolytic caps for everything in value they could get their hands on. I only took a quick look, but my impression was that the emphasis was on using the same value axials in as many places as possible (exceeding specs?). Yes there are lots of axial caps floating above the board with both legs bent under them, but man is not an auto insertion machine and there is no wave. My Eng friend scoffed at this, and grudgingly stated that if there was room in the box above the board that yes it would work. BTW this 1978 tuner works great, possibly better than new?

Lots of deigns have manufacture-ability and lowest component and materials costs as high priority goals. Total cost including trouble shooting and maintainability frequently didn't enter into the equation. Like my local City Council and Planning Board like to say and do, after the (connected) developer finishes "the school board can figure where to put the kids". I digress.

The products I was associated with had goals like 99.99 up-time and availability and MTTR of 15 min. Total cost overrode materials costs in almost every case, this also had the side befit of keeping the engineers, techs, installers, sales and the customers drinking together.

Short version: I'm not sure fidelity to the original design goals of lowest materials cost and manufacture-abilty should even be considerations in repairing the equipment (within reason).

* Electrolytic caps are a mature and stable tech, so differences that existed in the old days may not apply any longer. aka "quality caps are the same with different shrink wraps on them", there is no difference if they meet spec. Both my Eng friend and repair shop owner volunteer this opinion without hesitation. Given the pennys, and the limited quantities, I am willing to pay the premium for the FGs etc since the materials costs are only a few dollars difference. Maybe they are better.

* Component selection repairs, I understand that the mfgs want to put in parts from their QVL. I only wish they had put more info in their service manuals. Having to read the schematic ( one more new skill for me to learn) to determine the spec for a Cap is bush-league. You would think the silk screen, specs in the parts list, and specs on the cap would be sufficient.

My repair shop owner, when asked what determines the sound quality of an amp replied "everything" (transistors might be at the front of the line). Given that the difference in component costs on one of these projects is a few dollars for TOTL vs reg parts, I am willing to put in TOTL on the chance they actually are better.

Like some favorite CDs the Mac section is one I keep comming back to, friendly, many levels of knowledge and collaborative with common interested in the sound and equipment.

My 2 (20) Cents

 

[Gregory]

Psyching it out

There are more photos to present... whilst I psych it out!

No really, a lot of though is going into this unit.


Compandor board

Below is another photo of the COMPANDOR PCB with an original 47uF, 16V output coupling cap (in blue) and a proposed 47uF, 25V Muse KZ standing next to it.

The alternative is to install 47uF, 16V or 25V FG (Fine Gold) caps in there. Both 16 and 25 Volt FGs are small: 6.3 x 11mm in size.


Relative size of a premium grade Muse KZ cap with heavy leads compared to the other Compandor caps.


Equalizer board

Another good view of the Equalizer PCB. Looking for a way to recap it without taking the glass panel off, especially C723-24.

I'm not quite ready to go that deep into it yet. It's only 28 years old.


Eight electrolytic caps on the C33 Equalizer board. Can then be replaced with the PCB in place?


Monitor amp board

The Monitor Amp board should be easy to remove and recap. Must get the parts on order soon. Some may be in-stock already!

Will need to read-up on the bias pot adjustment, and do a before & after voltage check.


C33 Monitor Amp PCB should be easy to remove and recap.


Rectifier diodes

Do you think the power supply diodes need to be replaced? This isn't a high-stress piece of gear.

Oh, well how about the Monitor Amp? Now I'm seeing the + and -29 volt lines!


Original C33 power supply rectifiers seem to be ok? Replace them in another 5 years?


Wrap up

That's about as far as the C33 Update 2013 will go. It has been running too damn good to take the thing apart any more. Maybe in another 5 years or so.


Modern electrolytics are certainly good for it at this point in time.


-Greg

 

[jlovda]

I think you have to be careful, or have a lot of experience and confidence to change many dozens of caps on multiple boards, and change silicon all at once. Ask yourself.. what is the risk in doing this, or doing that? and how can a series of replacements be verified as successful? It's reasonable to separate a major project into stages with tests in between to be sure there are no issues. Might as well spread the enjoyment out over months, even years! :yes:


-Gregory

My problem is I have adult ADHD which means I'm impulsive. I do things first and then determine if I went about it the right way later.

The Rubicon caps that Mac used are nothing special, probably one step below FG. Second, if I buy my parts at Mouser, Digi-key or Newark I am getting OEM parts from the manufacturer. Mac buys them that way and I defy you to tell me someone measured every cap and resistor at the factory before installation. Some transistors are sorted and marked but I didn't touch them. Third, the audio Op Amp ICs (NE5534N) are standard parts that are still being made after 30 years. Maybe the available parts now are National Semi instead of Signetics but one of them is probably a second source for the other with equal or better specs. Using good quality parts, size and lead spacing were the main criteria. I changed EVERY electrolytic cap in my units and they sound great.

 

[Bubo]

My problem is I have adult ADHD which means I'm impulsive. I do things first and then determine if I went about it the right way later.

The Rubicon caps that Mac used are nothing special, probably one step below FG. Second, if I buy my parts at Mouser, Digi-key or Newark I am getting OEM parts from the manufacturer. Mac buys them that way and I defy you to tell me someone measured every cap and resistor at the factory before installation. Some transistors are sorted and marked but I didn't touch them. Third, the audio Op Amp ICs (NE5534N) are standard parts that are still being made after 30 years. Maybe the available parts now are National Semi instead of Signetics but one of them is probably a second source for the other with equal or better specs. Using good quality parts, size and lead spacing were the main criteria. I changed EVERY electrolytic cap in my units and they sound great.

OK, just don't start riding a motorcycle.

 

[Gregory]

Making progress

Slowly and methodically going forward with the updates. There are only a few original caps left in the Signal Path to change out. Have studied both sides of THREE large-format schematic sheets and am VERY familiar with the C33 from end to end.


New Op-Amps

Went ahead and ordered a dozen low-noise On Semi NE5534ANG Op-Amps on sale for 82¢ each (closeout price) from Newark.

On Semiconductor NE-5534ANG Op-Amp 10mhz Low Noise DIP-8

It came to less than 10 bucks, and I'm willing to do some chip-rolling for that price.


Muse cap leads and drill bits

Here's a simplified look at Cap leads and PCB holes. Let's start by examining all possible lead diameters for Muse KZ, FG and ES capacitors.


You will notice ALL leads on KZ caps are 0.8 mm (0.031") Dia. Only the lead spacing changes with cap diameter.




Cap lead diameters for FG series are limited to 0.6 mm (0.024") and 0.8 mm (0.031").




Cap lead diameters for ES series are also limited to 0.6 and 0.8 mm.




That means for any reasonable Muse cap.. the only DRILL DIA needed to open up PCB holes is 0.8 mm.


The perfect tool?

AFAIK the best tool for opening-up PCB holes when recapping is the following bit from Newark: Kelan drill bit 0.8mm tungsten carbide

The Kelan drill bits look to be made exclusively for drilling standard PCB holes, and come in 0.6, 0.8 and 1 mm.

Use as hand tool

It's good to see a 1/8" shank because wire-gauge drills aren't very stiff and often get damaged/bent. This is also good for Hand Operation.. and you could fit a rubber hose section over the shank for better grip and control. So there's no need to bugger McIntosh boards with slant-cut paper clips.


This was a very good discovery! Hope you've found today's Tech Note helpful.


-Greg

 

[CruzBay]

Always thought putting all low-noise op amps would be a good idea.

Wonder why Mcintosh only used them in the phono sections? Were they priced that far apart in the day? Gain different?

Hey Greg, should I buy a bunch of those devices for my components? (C-34v/C-29 and others)

Mike

 

[Gregory]

Always thought putting all low-noise op amps would be a good idea. Wonder why McIntosh only used them in the phono sections? Were they priced that far apart in the day? Gain different? Hey Greg, should I buy a bunch of those devices for my components? C-34v/C-29 and others?

You're asking me if you should buy some? Don't know.. I'm one that tends to leave silicon alone unless it has failed. Figured if they were discontinued, it would be a no brainer especially at that price and it would be good to have a set of ON Semis just for nostalgia. IIRC there are 10 total? so figure a couple extra.

Ask Ron-C. He suggested ON Semis in the C34V love series about 6 years ago, and check out C29 love about 7 years ago.


I wondered about a low closeout price, but remember the 5534A could be purchased direct from ON Semi for even less..

https://www.onsemi.com/PowerSolutions/product.do?id=NE5534AN​

Not anymore!


-Greg

 

[jlovda]

You show above the dimensions and wire gauges of the three Nichicon cap versions I assume you will be using. Have you already decided which type of cap you will be using in each location? What about the two large filter caps?

 

[Gregory]

You show above the dimensions and wire gauges of the three Nichicon cap versions I assume you will be using. Have you already decided which type of cap you will be using in each location? What about the two large filter caps?

I'll be using three types of Nichicon (now known as AVX) as outlined above in the C33. The two main power supply caps C1306-1307 were already replaced with Nich VZ. The plan is to replace a few of the Fine Gold (FG) caps installed in the power supply last year (critical C1311-1312 on the 18V lines for instance) with Premium KZ.

See example of Ron's power supply from 2007 below. Is this getting repetitive? Lol


Ron's photo of C34V power supply with larger Nich VZ in foreground and two KZ behind?


Will have to order some 3.3uF ES non-pols because there are NONE in my parts trays, and check stock for Monitor Amp caps.


FG or KZ?

So what do you all think about KZ for signal path coupling use? I now believe they are good for power supply and voltage rails, and the FGs are better suited as small-signal caps. This is not a lecture but an open discussion. What do you guys think about that??


-Greg