C33 Update Project 2013

[Gregory]

C33 Power Supply caps

C1311 and C1312 are "key caps" in the C33 IMHO.. the 100uF filters at the output of the +/18V regulators which go to several PCBs.




The large 4700uF VZ series filter caps are on the rectifier lines to the regulators, as are the disc ceramics.


The caps below C1311, 1312 are at the regulator outputs!


The plan is to change these to Nich KZ next time in there.


Reverse view

Here's another view of the layout. I like the idea of FGs there.. maybe even KZs?




When thinking about putting in KZs, you'd need to look a lead diameters and number drills.


-Greg

 

[Gregory]

Stage-1 update complete

The C33 is back together again after a week of updates starting Saturday Jan 12th.


Preamp on bench just before power was applied. It idled at ~24 watts.


Caps removed

Eight NP coupling caps and three FGs were installed in the Main PCB today. Here are the original 11 caps that came out.


Three Compandor caps on left replaced with Nich FG, other interstage bipolars on right with Nich ES.


A collection of 41 caps removed so far.


Assortment of original caps removed from Input and Main PCBs. Two from top PCB. Marking 039 refers to the lead diameter.


NEW coupling caps

The EIGHT non-polarized Nich ES caps (green) installed today are seen below.. two in the center, four in the upper right, and two in the lower right. There are two small FG caps in the far upper left which are INPUT CAPS to the VCAs (voltage controlled amps.) Going HEAVY on the sharpness control aGaiN.


Photo on mainboard looking from left to right with Green ES caps installed, two FG caps extreme left.


Compandor caps

A close look at the new COMPANDOR caps, two inputs on the RIGHT (C505, 506) and COMPANDOR CONTROL interstage cap (C522) at left. One of the originals (C506) was installed backwards at the factory. It's tricky.. the schematic is correct. Orientation becomes obvious when light shining through from the underside highlights the copper traces.

You will see a buildup of fine dust on the Main PCB. Will be looking at ways to remove it. Any suggestions? :scratch2:


Replacement Compandor caps are FG. Dust buildup on mainboard.


NP cap solder joints

Typical pads after resoldering and flux removal. They are highly reflective like mirrors!


Example of replacement cap solder joints. Slight residue from from deflux chemical is barely seen flowing behind right joint.


Reassembled

Later in the afternoon the preamp went back together. No trouble here except to mention the SCREWS (always harping on screws) were an odd lot of 6-32 x 1/4". I'll eventually replace all of these dissimilar hardware, and to avoid rust down the road.

Last minute inspection and photo taking..


C33 looking good on bench!! Is that solder hanging off the bench over the power strip?


What next

On the "to do" list is recap of Monitor Amp, the 5-band EQ board, and the Loudness, Balance and Compand board. Below are the four caps that are being eyed on the front LBC card. The blue 47uF will be replaced with either FGs or even KZs. The lead spacing is wide, it's just a matter of hole size.


Photo of LBC board came out GOOD for a low-level, existing light condition!


Will be able to connect and test the Stage-1 update soon. :yes:


-Greg

 

[Gregory]

You are doing a wonderful job there Gregory, I think you are making good decisions, getting the best out of what you have to work with.

Thanks Kevin.. let's look at how Ron did the C34V over five years ago.


C34V Love

You can bring up Ron-C's series of posts on AK: http://www.audiokarma.org/forums/showthread.php?t=140119


A photo of his PS section shows KZ caps for C1311, 1312 and other caps.


Ron-C's photo of his C34V new power supply caps.


There's still plenty of time to re-think, re-tool and change the PS caps.


-Greg

 

[c_dk]

After breaking a number of bits doing the 2nd or 3rd recap decided to "burr" and chuck up a good ole paper clip. Acts much like a cabinet scrapper to open up the hole and just bends if you bump it wrong. When it dulls just clip it at a diagonal again.

 

[jlovda]

Are you going to replace the four bridge rectifier diodes? I replaced mine with Vishay high speed glass types.

Also, I saw some 84 date code dual op amp ICs in a picture. Some people claim they get noisy with age. Mouser sell low noise TI's for less than $2 each. If nothing else change the ICs inside the phono shielded can.

John

 

[Gregory]

Are you going to replace the four bridge rectifier diodes? I replaced mine with Vishay high speed glass types.

Also, I saw some 84 date code dual op amp ICs in a picture. Some people claim they get noisy with age. Mouser sell low noise TI's for less than $2 each. If nothing else change the ICs inside the phono shielded can.

I ordered Fairchild 1N4007 (1000V, 1A) and 1N5408 (1000V, 3A) from Mouser, neither of which I'm too thrilled with. They have 1N5397 (600V, 1.5A) in stock which are 8¢ each.

You saw date code 84 in one of my photos? Which one? Like this one?




The strategy here is to order direct from OnSemi where I opened an account direct last year. Op-amps are relatively inexpensive.


A standard paperclip measures 0.032 Dia (1/32") with calipers.. which is a clearance hole for? 0.8mm? If you're going to order "number drills" from McMaster, buy 3 or 4 each. They used to come in small tan envelopes where you can mark down the size. I didn't measure a coat hanger diameter though.


-Greg

 

[jeffs79]

Another excellent thread, Gregory!

Your "updating" threads are among my favorites and I appreciate all the work you put into them.

Keep up the good work.

-Jeff

 

[jlovda]

I ordered Fairchild 1N4007 (1000V, 1A) and 1N5408 (1000V, 3A) from Mouser, neither of which I'm not too thrilled with. They have 1N5397 (600V, 1.5A) in stock which are 8¢ each.

You saw date code 84 in one of my photos? Which one? Like this one?

The strategy here is to order direct from OnSemi where I opened an account direct last year. Op-amps are relatively inexpensive.


-Gregory

Yes. I believe that is the 49th week of 1984. I believe those ICs in the picture are in the compander circuitry. The NE5534N are the low noise dual op amps that are in the audio path.

John

 

[c_dk]

When the twist of the drill pulls off a trace remember I warned you about twist drills. I plan on drilling out most of the main board holes, really helps with those soldered on both sides of the board

 

[Rich Andrews]

Please don't use a drill. One day a double or triple layer board will come along and the act of drilling the holes will damage the board. The dual and triple layered board holes are plated and drilling them out removes it. I made the mistake of drilling out holes years ago. Now I know better since I have had to repair my errors.

 

[Gregory]

Have fallen off the pace with this project and several others for two weeks or so.

The C33 was connected on Friday afternoon and it functioned well. I tend to think the sound is different.. BETTER, but no way to show an improvement with any measurement that is available here. The impression is there's more feeling of BASS in the floor, that is your feet can feel the drums, and for higher ranges of bass, not just the kick drum. I think the midrange sound is more focuses and detailed. Need to listen more. The sound from our DVD video last night was "cracking!"


There was a slight issue

I hooked the AudioControl to the RECORD External Processor jacks and tried sliding pairs of EQ pots up & down. The sound responded to each EQ, but at the TOP of each band.. approaching +15 dB, a squeal developed in each at the center frequency. Huh? what's with that? Re-connecting the AudioControl to the LISTEN External Processor jacks.. all was fine.

This is alarming because I didn't want to screw anything up while recapping and swabbing out phono jacks.

What do you suppose would cause an EQ squeal at the TOP of each band in the RECORD EXT PROC loop? I haven't checked if it's in one channel or both.


Generally the C33 looks marvelous, works marvelous and sounds.... marvelous!


-Greg

 

[Bubo]

Have fallen off the pace with this project and several others for two weeks or so. The C33 was connected on Friday afternoon and it functioned well. I tend to think the sound is different.. BETTER, but no way to show an improvement with any measurement that is available here. The impression is there's more feeling of BASS in the floor, that is your feet can feel the drums, and for higher ranges of bass, not just the kick drum. I think the midrange sound is more focuses and detailed. Need to listen more. The sound from our DVD video last night was "cracking!" << Brit expression. Lol

There was a slight issue

I hooked the AudioControl to the RECORD External Processor jacks and tried sliding pairs of EQ pots up & down. The sound responded to each EQ, but at the TOP of each band.. approaching +15 dB, a squeal developed in each at the center frequency. Huh? what's with that? Re-connecting the AudioControl to the LISTEN External Processor jacks.. all was fine. This is alarming because I didn't want to screw anything up while recapping. :nono:

What do you suppose would cause an EQ squeal at the TOP of each band in the RECORD EXT PROC loop? I haven't checked if it's in one channel or both.


Generally the C33 looks marvelous, works marvelous and sounds.... marvelous!


-Gregory

It would be interesting to observe the electrical characteristics of the in and out interfaces on the record circuit while you slide. Something between the cables and the Pre amp.

Then repeat it on a different interface, I suspect the problem is the IN circuit on the record interface on the pre-amp.

If you had a second EQ laying around, you could do a box swap approach, if all EQs cause the problem on the Record, then its the pre-amp. Maybe a second pre-amp if you have one laying around?

You can also check to see if the Record out is over driving or under driving at certain frequencies and EQ can't handle the deviation from its design spec gracefully?

Lets see, keep the record out, and switch the connectors from the EQ to a different interface and test the interface circuits on the pre amp this way by process of elimination. I assume all of the electrical characteristics are the same on a all interfaces.

You can also try turning off the on-board EQ on the pre-amp, bypassing it, to check for any effect and repeat on all other circuits on the pre-amp to see if there is any effect on the EQ problem (at low volumes or just headphones so you don't fry the speakers, maybe turn the amp off completely?

Hope this helps, sometimes the box swap approach is best for identifying "who done it".

 

[Gregory]

Still time to finish by end-of-year

There are FOUR months left in 2013 to finish up the project. Most or all of the parts have been ordered.

Let's see.. where were we?

1) Replace power supply FG caps with NZ, (FG's installed in Jan)

2) Look into replacing Op-Amps, (new ICs will have shiny, untarnished leads)

3) Recap Loudness Compandor PCB,

4) Recap Monitor Amp PCB,

5) Re-solder Phillips screw on Input PCB.​

The updated C26 and MC2505 are being used for DVD video in the mean time. Plus the 10 AWG power amp cables need to be rebuilt.


Front panel

I'm still leery about removing the front panel (ain't broke - don't fix it.) That could open-up a can of worms. Any foam-tape inside the front panel assy? or anything else that could drag-out the project?


Manufacture date

According to Roger Russell, C33 Preamps were built from 1981-1985, and according to John, the date stamp on the ICs is 49th week of 1984. That means the unit was probably built in 1985. So then 28+ years old? The update could have been put off for another two years.. huh?


-Gregory

 

[clinic-audio]

Hi Greg !

Last C33 arrived in France (new of course) was 22 novembre 1985 !

 

[kevzep]

Still time to finish by end-of-year

There are FOUR months left in 2013 to finish up the project. Most or all of the parts have been ordered.

Let's see.. where were we?

1) Replace power supply FG caps with NZ, (FG's installed in Jan)

2) Look into replacing Op-Amps, (new ICs will have shiny, untarnished leads)

3) Recap Loudness Compandor PCB,

4) Recap Monitor Amp PCB,

5) Re-solder Phillips screw on Input PCB.​

The updated C26 and MC2505 are being used for DVD video in the mean time. Plus the 10 AWG power amp cables need to be rebuilt.


Front panel

I'm still leery about removing the front panel (ain't broke - don't fix it.) That could open-up a can of worms.
Any foam-tape inside the front panel assy? or anything else that could drag-out the project?


Manufacture date

According to Roger Russell, C33 Preamps were built from 1981-1985, and according to John, the date stamp on the ICs is 49th week of 1984. That means the unit was built in late 84 or more likely early 85. So then 28+ years old? The update could have been put off for another two years.. huh?


-Gregory

Where does the time go???......:scratch2:

We will be watching with great interest, always enjoy your threads......

 

[jlovda]

C33 Preamps were built from 1981-1985, and according to John, the date stamp on the ICs is 49th week of 1984. That means the unit was built in late 84 or more likely early 85.

Remember, the unit could have been built "anytime" after 8449. Theoretically, the part could have sat in the warehouse for a year or two. You need to look through the unit and find the latest date code for a better guess.

 

[CruzBay]

Awesome work, Gregory, as always!

You taking on projects?

 

[Gregory]

Awesome work, Gregory, as always!

You taking on projects?

Thanks man! not clear on what you're asking. I'm about OUT of gear to update.

Would like to get some advice on what's inside the C33 front panel. Will there be rotting polyfoam eating away at the chassis paint? I feel there's a risk of damaging the litho behind the glass. Best NOT to mess with it unless there's a good reason.

No lamps seem to be out, etc.


-Greg

 

[Gregory]

Hi Greg ! Last C33 arrived in France (new of course) was 22 novembre 1985 !

Interesting bit of history

I moved to Chicago in June 1985, and bought the C33 on Nov 5, 1988. It was on consignment in a local audio store for 1200 bucks, which was a very good deal back then! Last new price was 2450. That means the preamp was ~3 years old and priced to sell because of an intermittent channel.

Used McIntosh were going for 2/3 last new price back in the 80's at E-Z Teletronics (now defunct). The `E´ in E-Z was Hank Engle who was store proprietor and service tech. What a guy! I used to visit the store regularly and he always had kool new Mc trade-in's on the shelf.

Would wheel and deal there. He liked that because I'd spiff up the units, bring them back (for the full amount I paid) and buy some kind of upgrade!!

Tinkering as usual.

The old guy has probably passed on by now.


-Greg

 

[CruzBay]

Thanks man! not clear on what you're asking. I'm about OUT of gear to update.
-Gregory

You know I've got some gear that'd use some TLC.