C33 Update Project 2013

[jlovda]

See example of Ron's power supply from 2007 below. Is this getting repetitive? :scratch2: Lol

-Gregory

Just wondering what your methodology is on selection of parts. I'm not trying to disapprove but it seems to be follow Ron-c's parts selection where it can be seen from photos and then move down the "quality" spectrum; KZ Muse if possible, FG second choice followed by ES Muse BP only where necessary. The important thing is that when you are all done and listening to the unit, you have a feeling of pride of a job well done. :yes: Remember to note the capacitor UNDER a bundle of cables a the left hand rear part of the main circuit board. It will have to be an odd "model" part with a very short length or the white cable connector will not go back on the mating female board connector.

 

[Bubo]

Someone mentioned that the caps were not individually tested in the old days.

My recollection, is that at the company I was working for in the early 80s, every component was brought in on tape, tested, and reassembled in sequence on tape to feed the auto insertion machines. We wound the transformers in house too.

I don't know what Mac did, but there is a good chance every component was tested in house before being fed to the auto inserters.

Again, my friend who is back seating me on my Yamaha amp, is a big fan of high temp caps in the power supply, his team designs machines for electronics factory floors.

For a few pennys more, why not?

Heat kills.

 

[perryinva]

I'll throw in my 2 cents, since I still have 2 C33s to recap and a 2105. The 105C audio caps almost always are closer to the stated value than a comparable 85C cap, KT and KA vs FG and KZ. I'm surprised no one has mentioned this. The high temp ones have a longer predicted life at spec as well, per the spec sheets. The old a cap is a cap is not really the in an audio path because how it handles different frequencies and the distortions at level all come in to play with regards to the sound. That said, I do believe that virtually any audio grade cap today is far better than any 30 year old cap currently installed so you can only go UP, the question is, how much more UP is worth the trouble? KZ with their high voltages and large leads is overkill and may actu give poorer performance at a small fraction of their actual voltage use. A 100V electrolytic in a 6v circuit is silly and gains nothing.

 

[Gregory]

Just wondering what your methodology is on selection of parts. I'm not trying to disapprove but it seems to be follow Ron-c's parts selection where it can be seen from photos and then move down the "quality" spectrum; KZ Muse if possible, FG second choice followed by ES Muse BP only where necessary. The important thing is that when you are all done and listening to the unit, you have a feeling of pride of a job well done.

Have spent a lot of time, literally at the drawing board where the schematics are laid out, thinking about the update: cap values, lead diameters, hole sizes, etc. The new philosophy in to steer away from big 10uF, 100V KZ caps in the signal path because Nich says they are "Premium audio grade." Instead looking at tiny 5x11 mm FG caps. All Nich FGs below 22uF (including 10uF, down to 0.1uF) have a minimum voltage rating of 50V, are in the tiniest case size of 5x11 mm, and are Temperature rated -40 to 85°C.

For example, the 10uF polarized caps on the High Level Input PCB are 16v, not 100V. See voltage rating on schematic for C426-427.

I'll be putting KZs in the power supply and using FG/ES for interstage coupling. Agree or disagree, it will stimulate the group to rethink what a small-signal coupling cap is. :thmbsp:


-Gregory

 

[jlovda]

I'll throw in my 2 cents, since I still have 2 C33s to recap and a 2105. The 105C audio caps almost always are closer to the stated value than a comparable 85C cap, KT and KA vs FG and KZ. I'm surprised no one has mentioned this. The high temp ones have a longer predicted life at spec as well, per the spec sheets. The old a cap is a cap is not really the in an audio path because how it handles different frequencies and the distortions at level all come in to play with regards to the sound. That said, I do believe that virtually any audio grade cap today is far better than any 30 year old cap currently installed so you can only go UP, the question is, how much more UP is worth the trouble? KZ with their high voltages and large leads is overkill and may actu give poorer performance at a small fraction of their actual voltage use. A 100V electrolytic in a 6v circuit is silly and gains nothing.

From looking at catalogs, I have never seen 100 degree caps described for audio application, not that they wouldn't work perfect fine. The Muse and Fine Gold are pushed for those applications. Regarding values and tolerances, I believe normal specs are -20% to +100%. I have used 33uf in 20uf spots in audio path applications without any trouble. A higher capacity just has a lower corner frequency. I would never use a smaller value. Just don't change the value for a timing cap used to control a relay, etc.

As for the longevity of your work, if you are 30-35 years old this analysis may be relevant. If you are 65 yrs old like me it is irrelevant.

 

[Bubo]

From looking at catalogs, I have never seen 100 degree caps described for audio application, not that they wouldn't work perfect fine. The Muse and Fine Gold are pushed for those applications. Regarding values and tolerances, I believe normal specs are -20% to +100%. I have used 33uf in 20uf spots in audio path applications without any trouble. A higher capacity just has a lower corner frequency. I would never use a smaller value. Just don't change the value for a timing cap used to control a relay, etc.

As for the longevity of your work, if you are 30-35 years old this analysis may be relevant. If you are 65 yrs old like me it is irrelevant.

I'm a little short of 60 myself, so yes if the new caps deliver same 30 year performance as originals..... I'm in pretty good shape.

I have a bunch of Yamaha stuff I am ramping up for, for the same uf sometimes there are 3 or 4 different V requirements so I am picking the highest voltage and ordering a bag full of FGs to use across the products.

For the PS filter caps, I am going with the high temp models and FG for everything else if possible.

 

[perryinva]

As I mentioned, 99% sure both KT and KA are 100C rated and are specifically designated audio grade. And you're right, at 56 anything I put in will outlive me, but that's not the point, IMHO, it was to generate some discussion. Rarely in a signal path, does the actual -20/+100 spec become actually acceptable especially for LC, cutoff, filter, and bypass caps. Ground coupling and loadind ones make less difference, but of course, I agree it makes no difference if it is a 10.1uF or an 11uF in most cases, and any of the premium audio have been in the 5% range at least anyway.

 

[Bubo]

As I mentioned, 99% sure both KT and KA are 100C rated and are specifically designated audio grade. And you're right, at 56 anything I put in will outlive me, but that's not the point, IMHO, it was to generate some discussion. Rarely in a signal path, does the actual -20/+100 spec become actually acceptable especially for LC, cutoff, filter, and bypass caps. Ground coupling and loadind ones make less difference, but of course, I agree it makes no difference if it is a 10.1uF or an 11uF in most cases, and any of the premium audio have been in the 5% range at least anyway.

Perry,

I'm on a steep learning curve, and in possession of a lot of 30 year old gear that I would like to update before something goes bump or smokes aka its all working now.

To be effective, I am trying to purchase the best quality (within reason) and components that I can use on the 10 Yamaha products I own, all from the same period and product lines. So where I see commonality, I am consolidating the capacitor types and buying them in 25 to 50 piece lots. Once I am through the Yamaha stuff, I plan to move on the Mac gear at which point I should be able to make a good solder joint with the caps inserted in the right direction.

The next hill I have to climb is out of production transistors (op amps) and suitable replacements, I have to learn which specs are flexible and which are not.

One of the more creative posters on the Yamaha site added a soft start (relay) to the 30 year old 160WRMS amp he is rebuilding, this seems like an interesting topic worth discussion when updating old equipment. Less stress is more life since components aren't weakened over time. To my uninformed eye, this appears to be just the addition of a soft start relay in line with 120VAC as it enters the system. The ones I am seeing are in the $80 range with just one manufacturer, steep.

Short version: I appreciate any discussion on any aspect of updating our treasured stereo equipment, mine literally makes me happy every-time I enter the room and the music is playing. Isn't the whole purpose of these discussions to test ideas?

If we can make the equipment better than new, why not?

 

[Bubo]

Interesting kit suggestion from bktheking

$14 for a soft-start kit.

I may be purchasing a few of these.

http://www.ebay.ca/itm/Soft-startin..._Audio_Amplifiers_Preamps&hash=item4a9b152593

 

[Gregory]

Parts arrive

The shipment from Newark arrived yesterday with the Op-Amps and PCB drilling tool.

Here's a look at one of the NE5534ANG chips after adjusting contrast and being careful not 'go overboard' with the sharpen filter.


ON Semi NE5534ANG with date code 2013 week 20? How do you like THAT image?


How excited can one get over a 82¢ chip?

What are the ESD precautions if any?


PCB mod bit

The 0.8mm PCB bit is tiny.. only 1-1/2" long. I'm looking forward to 'opening up' a few component holes in the Mainboard, working it manually with great care that is. Will report how it goes and if there are any 'pad' issues.


New precision bit from Newark Elect for opening up 0.6 mm PCB holes to 0.8 mm.


Hole and Lead diameters

Just a few words on PCB hole and component lead diameters. Some time ago I labeled the Ziplocks 0.031" and posted that Nich caps had 0.031" leads. Well that's INCORRECT. One really needs to check the diameters with calipers!!

Below are Ziplock bags correctly marked with a LEAD DIA of 0.028". The 0.8mm hole size is 0.031".


Ziplock bags of replacement Nichicon caps originally labeled with Hole diameter.. not Lead diameter!


So these are the finer points in determining what size hole is needed and what suitable tool to use.


-Greg

 

[jlovda]

Boy, am I glad I finished my recap projects long time ago.

 

[Gregory]

Just wondering what your methodology is on selection of parts. I'm not trying to disapprove but it seems to be follow Ron-c's parts selection where it can be seen from photos and then move down the "quality" spectrum; KZ Muse if possible, FG second choice followed by ES Muse BP only where necessary.

Here's another example for you John

C426 behind the proposed 100V KZ is a stock 10uF 16V electrolytic on the RIGHT LISTEN OUT line.


Photo of Listen Out cap on the RIGHT INPUT PCB with proposed 100v KZ replacement. Photo taken in January 2013.

Would a 100V KZ be better in that location? or a FG in the smallest case size of 5x11 mm? Think about that for a bit.


Ended up putting in FGs earlier this year. The High Level Input caps could be upgraded again at some point in time.


Repost: Nich Find Gold caps installed in January of this year. Don't worry about the Sharpie markings. They come off easily with acetone.


This post is also meant to show more kool photos of the C33. There are so many pics now, I barely need to open the chassis.


-Greg

 

[jlovda]

100v cap in place of 16v? That seems really illogical. The size of the leads on that KZ looks like it can handle 10 amps. I would stick to something closer to the original; possibly 25v or 50v tops.

 

[Gregory]

Loudness PCB recap day

Enough parts came in last week to resume C33 Updates and recapping.

There was a head-scratcher right off the bat. Seems one of the stock caps C615 was in backward.


2-pin connector in center brings -18 and +18 Volts to the Loudness board.


Replacement caps

The Loudness PCB electrolytics are all Fine Gold now. Pretty sure the replacement caps are in correctly. Voltages were measured and cap polarity confirmed.

Still thinking of `going for it´ and installing 47uF KZs in Loudness Amplifier output circuit. :scratch2:


Loudness amplifier output coupling caps. Blue polarity markings will be removed with solvent.


Measured Voltage

Due to the cap mix-up, voltages were measured at the Loudness PCB, working upstream to the power transformer.

• Voltage on 1uF caps AFTER replacement: +17.86, -18.38 -- The spec is: +18V, -18V, +/-0.9V
  
  
• Voltage into PS regulators IC1301-1302: +28.4, -28.6 -- The schematic reads: +29V, -29V
  
  
• Voltage at power transformer output: 21.5, 21.5 VAC -- The schematic reads: 20, 20 VAC

KZs in Power Supply

The FGs installed in Jan 2013 for C1311-1312 were replaced today with KZs after rethinking the situation. Woo-hoo!


Caps C1311-1312 replaced twice this year, first to FG and now to KZ. Suppose those babies will beautifully couple audio to ground. Lol


TT Sens pot

The Auto-On sensitivity pot doesn't seem to have a connector.. maybe inside the bracket? It's awkward and very much in the way!

Here it's wrapped in foam to avoid damage to the circuit boards.


Turntable auto-on sensitivity pot wrapped in foam so it won't 'bang' and can be tucked.


Wrap-up

I'm really not sure if the type of replacement caps installed in the C33 were the best choice. Of course the highest quality is desired in the Audio Path. Suppose any caps today are better and more uniform than those 30 years ago. So I've turned a perfectly good C33 into a "project." Not sure if it was time to do all this yet. Once you go down that road... where does it end?


That's about it for today. Only four hours of futzing, and that includes getting tools out and setting up. This update process is not to be construed as 'the best' way to recap a C33... it's way over the top actually.


-Greg

 

[Gregory]

Back to the drawing board

Ha! very funny.

Schematics are laid out for convenient circuit and parts list reference on a drafting board.


Drawing board near workbench for easy schematic check that was recreated in Oak and Formica from one built as a kid out of scrap wood.


Monitor Amp recapping

It seems we're getting a little too boutique with replacement caps. I was uncomfortable presenting the Loudness PCB with all Fine Gold caps yesterday and would like to use appropriate caps going forward. The objective is to return the unit to its original condition, right? and not get too fancy. We'll look more into cap selection below.

It was easy to remove the Monitor Amp, and good to have it on the bench for easy servicing. Suppose a fixture could be built to test these boards on the bench.


BEFORE view..


C33 Monitor Amp PCB on the bench with original caps. Removing this board is easy.. four inline plugs and two screws.


A look at the power transistors. More mid-1984 date codes.




Rethinking which caps

It was clear that the Nich KZ caps intended to go into the Monitor Amp were physically too big, and that some of the filter and shunt caps didn't need to be Premium Audio type. Here's a Nich VR cap that was on-hand from a couple years ago. C1013-1014 appear to be some kind of shunt caps in the feedback loop of the differential pair driver circuits?


Nich VR electrolytic next to the original cap from differential pair driver circuit.

The decision was to install two 47uF Nich VR caps for C1013-1014. It seems a VR cap would be just right for the time delay circuit too!


Solder pads

A close-up view of the Monitor Amp solder pads. Not sure about you, but at 55, I can't see as well compared to years ago.

These pads could use another swipe of solvent.


You can take a pic with a digital camera and immediately zoom in REALLY close to check work.. and have a photo to post later!


Mc Parts Dept

A basic 10uF 50V cap was ordered from McIntosh Parts a few years ago to see what they would supply.

No boutique cap! it was a no-nonsense high quality cap.. thank you very much. :yes:


An ordinary 10Uf 50V cap ordered from McIntosh Parts... to see what they stock.

One of those VR caps was used to replace the original time delay cap (center of board.)


Front end of Monitor Amp complete

Decided to leave the final amplifier stage STOCK for now and rethink what caps to use some more.

Here you see the front end of the C33 Monitor Amp has been recapped. I'd also like to look at the 'before' bias voltages first.


AFTER view..


These seven new Monitor Amp caps are tiny and I'm glad to have 'em there. Four caps in the FINAL stage will be replaced soon.


BIAS voltages

The C33 Monitor Amp BIAS voltages were measured FOUR times before connecting it into the system.


The spec is 5mV between resistors on the component side of the PCB for both Left and Right channels.

C33 Monitor Amp BIAS voltages

 Test#  Left(mv)  Right(mv)
 -----  --------  ---------
   1       38*      10.1
   2       28*      10.3
   3      8.9       10.8
   4      9.0       10.8

      * bad connection

Summary

The input (front end) of the C33 MA has been recapped with Nich ES and VR electrolytics. I think these caps are just as good or better that the originals. The C33 with internal amplifier is connected to the speakers and playing right now.


What McIntosh needs is a good 20 Watt amplifier. Well you got it! :thmbsp:


-Greg

 

[dubai2000]

Very interesting thread! I am recapping my MA 6200 at the moment and was wondering if those 2.2µF caps on the input terminal board (meaning next to the RCA inputs) actually need to have this value. I suppose they are meant to block any incoming DC, so wouldn't a smaller value also be adequate? Like this one could use small film caps which I rate sonically superior to any electrolytic cap. Or could one even keep them out completely? In my amp they are only connected to both AUX and the Tape input.

Your thought will be appreciated.

Wolfram

 

[Bubo]

Very interesting thread! I am recapping my MA 6200 at the moment and was wondering if those 2.2µF caps on the input terminal board (meaning next to the RCA inputs) actually need to have this value. I suppose they are meant to block any incoming DC, so wouldn't a smaller value also be adequate? Like this one could use small film caps which I rate sonically superior to any electrolytic cap. Or could one even keep them out completely? In my amp they are only connected to both AUX and the Tape input.

Your thought will be appreciated.

Wolfram

Once you settle on a value, you could take the circuit outboard (breadboard) and do shoot out with different materials capacitors and
the effect on sound quality. It might be both fun and the results may be interesting if you have the time. If you do it, be sure to post the results.

 

[Gregory]

Very interesting thread! I am recapping my MA 6200 at the moment and was wondering if those 2.2µF caps on the input terminal board actually need to have this value. I suppose they are meant to block any incoming DC, so wouldn't a smaller value also be adequate? Like this one could use small film caps which I rate sonically superior to any electrolytic cap. Or could one even keep them out completely? In my amp they are only connected to both AUX and the Tape input. Your thought will be appreciated.

Yeah.. it's enjoyable to update these units and keep 'em running and looking like new, so long as nothing gets broken! It would be best not to modifying your amplifier or changing values too much IMHO. The only time I recall upping values was increasing an NP input cap from 0.47 to 1uF, and buying main power supply caps there were slightly higher capacitance.

The main issue here is `what series of Nichicon electrolytics to install in various circuits.´ Most Mc threads on AK advocate following what's in the schematic and parts list. Someone who's a capacitor expert will have to advise you on film caps. I wouldn't remove or short the high level input coupling caps at all. Not many people are chiming in on the C33 cap recommendations. I'm making some bad choices and probably looking like a fool. So if you read through these posts and see something that's odd, then it's useful.

As stated before, these threads aren't tutorials or lectures, they are discussions. I'll probably go back and change the Fine Golds to KZs in the signal path after all, maybe by the end of the year. Must do more homework first.


-Gregory

 

[jlovda]

Very interesting thread! I am recapping my MA 6200 at the moment and was wondering if those 2.2µF caps on the input terminal board (meaning next to the RCA inputs) actually need to have this value. I suppose they are meant to block any incoming DC, so wouldn't a smaller value also be adequate? Like this one could use small film caps which I rate sonically superior to any electrolytic cap. Or could one even keep them out completely? In my amp they are only connected to both AUX and the Tape input.

Your thought will be appreciated.

Wolfram

The cap is passing AC. The capacitive reactance of the cap must be sufficiently lower than the input impedance of the circuit the capacitor is looking into so that it can pass at all desired frequencies. The reactance of a capacitor is Xc=1/(2*PI*f*C). Typically Xc is made at least 10x lower than the input impedance it's coupled to. Example: If the input impedance of the preamp is 50 K ohms, Xc would need to be <= 5 K ohms. For 20 Hz, the capacitor would have to be larger than 1.6 uF. If you put in a 1 uf cap, the rolloff frequency would go up to 32 Hz. I don't know what the input impedance of Mac preamps are but you can see lower value caps would be detrimental.

You probably could eliminate the input caps if you were sure there was no DC coming in from the source but don't trust me without checking somewhere else as well.

 

[Gregory]

Once you settle on a value, you could take the circuit outboard (breadboard) and do shoot out with different materials capacitors and the effect on sound quality. It might be both fun and the results may be interesting if you have the time. If you do it, be sure to post the results.

That might be good in the lab.. but this isn't `beater gear´ man!

LOL - ok we're laughing here!


-Greg