C33 Update Project 2013

Gregory

Soundco Kid
Let's get started on the C33 which is 28 years old now.


Finally underway

The C33 is update is finally getting started after YEARS of procrastination. When did Ron-C do the C34V? Dec 2007? That's how long ago. The plan is to service the HIGH LEVEL INPUT boards first, then the Power Supply. Let's have a look at some Power Supply photos.


Main power supply caps


The NEW Nich 4,700uf VZ's @35V are similar but physically smaller that the originals.

C33_main_caps.jpg


Power Supply rectifiers

C33_rectifiers_I.jpg


Rectifiers in the rear-most compartment

C33_rectifiers_II.jpg
There appears to be (at least) eight 1N5395 diodes in the C33. I may replace them with Fairchild 1N5408.



There was some trouble finding suitable diodes. The Parts List says they are 400V, 1.5A type and I haven't found a GOOD replacement, except for the Fairchild 1N5408 which are 1000V, 3A. The lead diameter of the existing diodes is 0.032".


Top cover PCB

The first board was removed and JUICED UP with Deoxit. I see the TWO caps at the end are in the signal path.

C33_top_cover_PCB.jpg
Two caps at the end look like general purpose electrolytics. These will be replaced with FG (Fine Gold.)



They are 10uF, 50V when the schematic calls for 16V. Will need to order FG for these.

C33_top_cover_caps.jpg
10uF caps on top PCB. There was a small rust spot in the center of the Monitor Amp INPUT switch which came off pretty well but left tool marks.



End of Day 1

Suppose someone could go through this preamp in 4 - 6 hours but how many things would get broken? What corners would be cut? It's going to take easily 4 - 6 weeks to do this job.. and possibly longer.


But it will be fun. :thumbsup:


-Greg
 
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Great Stuff Gregory, you sure are busy......
You are going to run out of gear to work on at this rate.....:thmbsp:

But then where I live it is summer, and we are all spending time outside and at the beach swimming in the Ocean!!
 
Anyone claiming a 4 hour C33 recap is blowing smoke...and false ego on top of that. Using FG type caps is much easier than KZs, which will need more lead hole drilling and are much more difficult to fit.

A labor bill of 7-8 hours with lamp replacement is about right.
 
Gregory, one thing that will help in drilling out screws\bolts is a set of left hand drill bits. Fairly expensive for the large index but use them once and they pay for themselves in stress reduction. Many times I've drilled out screws\bolts and had the reverse action of the drill bit unscrew whatever was stuck. Try and find cobalt bits and not the TiN plated imported junk.
 
Go to Home Depot and get one of these.

The hex at the handle end will make removing tight screws a breeze assuming a combination wrench is used.

bd05c945-e90f-4ac0-8e90-849da6352ff1_300.jpg


If a #1 is needed then a nice fat handle is needed like this one.

73073de0-eb2a-4408-b125-87847c15d7e8_300.jpg


The Husky Pro screwdrivers are actually good ones. They fit better than Craftsman.
 
Hi Gregory,

Have you tried heating the screws with a soldering iron? More then over torque, it seems like the years have set the screws in place. A gentle heat might help loosen the screw a bit.

Cheers
 
Things are going much better today, and thanks for all the input.


Ordering parts/supplies

Spent much of the morning reviewing specs and order caps/supplies/tools.. three new Xcelite Phillips drivers, more solder wick and additional (or higher voltage) VZ power supply caps. The size is not an issue these days. Also ordered a half dozen of so 10uF Nich FG (Fine Gold) and FW for evaluation.

Note to Rich.. maybe it was premature to order Xcelite screw drivers, and I'll look at Husky over at Lowes next week while picking up some acetone... supply is about exhausted.


Recap High Level Input boards

After ordering stuff this morning, the LEFT & RIGHT Input PCBs were removed and most of the caps replaced already. Only one of the thru-chassis PCB screws was EXTREMELY tight, and it `SNAPPED´ loudly when breaking free. I see the rear PCB screws are dissimilar now. The vias (solder pads) on the INPUT boards are tiny and you almost need a magnifying light to work on them. The joints were inspected with the camera zoom in macro mode. Yep there's extreme close-up pics of each cap solder.

Will have a more detailed report this evening.


Cap inspection

Not thinking of each step thoroughly, I installed ten 2.2uF NP caps at the inputs without testing them, but later (on the three-gang clusters) the 10uF were measured on the DMM for variation, and they were matched-up in pairs L - R. This isn't really necessary but is something you can do when you have all day. The results of the 10uF NP measurements are:

10uF NP caps measured on DMM
Code:
Measured   Corrected  (0.87735 correction factor)
--------   ---------
 12.20      10.70
 12.00      10.53
 11.79      10.34
 11.80      10.35
 11.80      10.35
 11.39       9.99


That last cap could have been thrown out, or paired with another low one. The Capacitor "CAL meter factor" was found during XR6 work. :)


Input phono jacks

The input RCA jacks have a lot of stain and tarnish? on the inside. Have seen 0.110" swabs on Mouser site and think those could be used to "rod out" the jacks. Here are a few images of the RCA jacks from inside.. on top.

Input_jacks_I.jpg


Close-up and super sharp... you can see where the plug Center Pin scrapes along on the inside of the connector. All that solder on the inside of the chassis could make it difficult to install new RCA jacks someday, the kind with hex ring nuts.. which is why it's good to take care of the originals.

Input_jacks_II.jpg

I'd imagine these would clean-up pretty well with the right solvent. There were no glaring issues on the rear INPUT assemblies.


Nothing got broken today.


-Greg
 
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Hi Gregory, Have you tried heating the screws with a soldering iron? More then over torque, it seems like the years have set the screws in place. A gentle heat might help loosen the screw a bit. Cheers

Hey that may be a good idea. Anything in moderation huh? Obviously an impact driver can't be used. You're probably right.. the black oxide coating may have reacted somehow with the receiving threads. One thing I don't mind investing in is NEW tools. I like Rich's idea of the Lowes brand Phillips. :D


-Gregory
 
I have been cracking these things open for 30 years with none of the screw issues you seem to have......knock on wood!
 
Very busy day... and backed up again tonight like last night!


Cable reference photo

A snapshot of the cables and connectors on the Input boards taken for reference when it's time to reinstall later on.

Input_PCB_connections.jpg
Input boards cable re-connect reference photo.


Removing High Level Input boards

Fortunately the FOUR screws that hold the Input PCBs to the rear chassis came out w/o much trouble. One screw was VERY tight however and required extreme of force to "crack" it free. I noticed three of the screws are a shiny copper/black color, and the oddball is flat black. The LEFT Input PCB screws are similar.

LEFT input board

C33_left_input_screws.jpg
I think those circles on the bracket are from the plating process, and nothing to worry about.



RIGHT input board

The RIGHT Input PCB screws are dissimilar. It appears the ORIGINAL screw is flat black (on left in pic) and that's the one that was frozen/ceased in place. The screws are back in the brackets to retain them. I've checked these for 0 ohm resistance through the plating/coating.

C33_right_input_screws.jpg
Odd-ball screws on the INPUT board. Odd screws bother me and get upgraded to black or bright stainless steel type.


Recapping the Input boards

The HL Input board were removed with ease. A photo of the two in original condition is seen below. Strange the P/N ink (or the right end) is different between the two boards, and the on-board buss wire jumpers are of DIFFERENT material. I've marked LEFT & RIGHT with a blue Sharpie on the ends temporarily (see on far right near PCB P/Ns below.) Dissimilar parts have always bothered me!!

Also notice the transistors on the LEFT end of the lower board have white paint on top. Puzzling.. the three transistors in front of them are mounted HIGH from the board surface, and are bent and crooked as hell.

C33_Inputs_before_II.jpg
Reference photo of LEFT and RIGHT INPUT boards.


The chassis without the Input PCBs. The TT sensitivity pot is hanging on stiff wire in the right front. Top Panel PCB and cross-bracket have been removed.

C33_apart_Inputs_out.jpg
Photo of C33 with INPUT boards and Top Cover Controls assembly removed.


Desoldering

Below is a photo of the LEFT Input board pads where the original 2.2uF NP caps were soldered. The joint was heated and the caps "rocked" out from the component side, first to one side, then the other while heating. Solder wick was used to absorb excess solder, after which the area was scrubbed with acetone over the sink.

LEFT Input PCB

C33_Input_desoldered_II.jpg


Stuffing

New 2.2uF, 50V Nichicon ES caps going into the RIGHT board. One lead of each cap is already soldered and snipped off. This trick can help if you want to get the components in straight and perpendicular. :smoke:

C33_Input_stuffing_I.jpg


Resoldering

The 2.2uF NP caps soldered in place followed by another acetone scrub to remove flux. Not too shabby. :thumbsup:

LEFT Input board

C33_Input_re-soldered_II.jpg
View of the LEFT PCB. A partially cracked ground-screw solder joint in pointed out with YELLOW arrow.


Changing out 10uF NPs

Last step for the day was to install three 10uF ES caps in the lower left corner of each INPUT board.

The original 10uF are the dark blue caps on the bench mat and the original 2.2uF are "in the bag."

C33_Input_triple-clusters.jpg
Input PCBs on workbench.. kitchen counter that is. Solder sponge is in grandma's old jelly dish!


Soldering tools

The solder sponge above is nothing more that an ordinary sink type (with green Scotch pad on the back) that has been squared-up and the corners snipped off to fit. I had that Weller solder iron and stand as a schoolboy in the 60-70's. It still has the original tip!


Below is a photo before putting her to bed for the night. :thmbsp:

C33_Inputs_aprt_II.jpg


Summary

The High Level Input boards are mostly done, with the exception of 2-each 10uF polarized electrolytics in the signal paths. Those parts are on order.


-Greg
 
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Gregory,

The height of the components on the boards may have had something to do with the type of auto insertion machine used at the factory or the sensitivity to heat of the individual components as they flowed through the wave solder machine.

Looking at the boards, they remind me of the early auto dial modems we use to make which were almost entirely auto inserted.

Again, I'm just the Marketing Guy
 
The height of the components on the boards may have had something to do with the type of auto insertion machine used at the factory or the sensitivity to heat of the individual components as they flowed through the wave solder machine. Looking at the boards, they remind me of the early auto dial modems we use to make which were almost entirely auto inserted.

Have a look at these pics.. still processing images from earlier today.


Left channel

The LEFT Input PCB has the "whitecaps" and the high, crooked transistor devices in front of them. I've got a good mind to correct that situation, but why mess with it if it's working ok. Odd ball and dissimilar parts bother me a lot.. too much like General Motors. :sigh:

C33_transistors_Left.jpg
Not too happy with the way the transistors in the foreground are installed. The 470 ohm resistors look like crap.



Right channel

The RIGHT Input PCB arrangement looks normal. Those resistors don't seem to be the best quality!!

C33_transistors_Right.jpg


Inputs boards - Day 2

The Input PCBs at the end of day 2 with eight NEW NP caps each. Replacements for the two polarized caps (BLUE, lower left) are on order. Also notice an extra row of caps on the LEFT Input PCB (at bottom.)

C33_Inputs_day2B.jpg


Whew.. a lot of report writing lately. Going bananas! :banana:


-Greg
 
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Those caps look like the same ones that Mc used in the MQ107/MQ108 I was told they are metalized polyester caps. Good for many decades according to Roger.
 
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Since more caps are on order.. nothing much was accomplished today.


Rear panel Input Jacks (before)

Below is a photo of the input jacks after disassembly on Jan 13th.. when I commented about contamination on and inside the jacks. There's solder flux plastered on the chassis/mounting bracket and inside the center receptacle

Input_jacks_before.jpg


Rear panel Input Jacks (after)

Today I got out the cotton-tipped wooden swabs and denatured alcohol / mineral spirits cans. Both of these chemicals dissolve flux, and MS (actually lacquer thinner) will remove the black tarnish. It's slow going but comes out great!

Input_jacks_after_I.jpg
Lots of factory solder flux removed from the rear INPUT jacks.



More rear jacks

This is typical all the way down the line of rear panel jacks. An aluminum bar with 11 pair of RCA jacks is attached to the chassis with three pair of screws from the back. That whole "input bar" can be dismounted for inspection. Wouldn't you think, if the screws have "ceased" inside the threads, that breaking them loose and re-tightening would be good?

C33_input_jacks_bar.jpg
Red arrows pointing out screws holding INPUT PCBs to the chassis.



All this attention and detail work takes time. I'm sure it will pay off with long term satisfaction and a pristine amplifier. :)


-Greg
 
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Another update on the C33. While waiting for parts orders to arrive, there's plenty of time to study the schematic and do a lot of detailing.


Input connector bar

The high level input connector assembly was removed today. Great care is taken to prevent dings and scratches!

C33_input_bar_II.jpg
Three pair of two #6-32 screws hold the assembly in place. The center two have lock washers.



Spots in the plating

Let's look at those spots up close. Seems they have to do with the plating process? In the center of the photo are two threaded holes.. which later were cleaned-up with a 6-32 tap. They were buggered somehow.. but not badly. Screws should go into those threads easily and not require much screw driver torque!

Electrically speaking, running a tap in there is better than deoxing.

C33_input_bar_III.jpg


Inspect and replace screws

Best to check these screws for rust and replace if necessary. I'm in the habit of upgrading screws to stainless steel.

C33_input_screws.jpg


Preparing to deflux

Now we have the connector bar on top of the amplifier with a view of FLUX residue around the jacks. You're looking at the MAIN and Switched Outputs.

C33_BBM_jacks_I.jpg


External Processor jacks

The external processor feature on this preamp is excellent!!

Below is one of the External Processor jacks with black "jumper wire" that goes between the Input and Output ports. This is a GREAT feature as long as the connections are working ok. What do you suppose that BLACK tarnish is?

C33_BBM_jack_I.jpg


Defluxing

Below is the Input Jack Assy about half way through the deflux process. No drips or runs got into the preamp.

An ordinary household place-mat was used as a solvent barrier.

C33_jacks_after_I.jpg


Close-up of treated External Processor jacks – Before and After defluxing.

C33_jacks_before-after.jpg


This task is nearly complete


C33_jacks_after_III.jpg


Swabbing out phono jacks

Wooden handled 3/16" cotton-tipped swabs come in REAL handy for cleaning out the RCA jacks. I must have gone through 8 to 12 of them today. Dipped in denatured alcohol (DA) they squish down to the jack inner diameter and rod the innards out real well. A good amount of crud and dirt was removed as evident from the color of the tips. All this to decontaminate and rejuvenate the preamp.

Does that thread look buggered to you? :scratch2:

C33_jack_swab_II.jpg


Summary

Not much going on today beside studying and defluxing. A few additional points to make.

1) Threads in the connector bar were cleaned up with a 6-32 tap, after which the screws when in like they should,

2) Ninety nine plus percent of the old flux was removed from the connectors between yesterday and today,

3) Mounting screws were tested for 0.0 ohms through their coating,

4) The connector assembly has been re-installed in the preamp,

5) Screw driver issues are pretty much sorted out now.​


Suppose a thorough deox of the jacks, mating surfaces and threads makes for a good quiet ground.


Soon we can get back to electronic Tech work. :thumbsup:



-Greg
 
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Wow.. three orders came in today!

Lots of caps to replace now

The postman delivered three shipments of caps, supplies and tools this afternoon.. all inventoried and sorted. This installment of the C33 thread is to compare two different voltage ratings for the MAIN POWER SUPPLY CAPS. Ordering 35V, 4700uF and seeing how small they were, I noticed the size is still smaller that OE when going to the NEXT HIGHER 50 volts.


Which PS cap to install

Let's have a look at a 50V and 35V, 4700uF cap side-by-side. Either will meet the spec of 35V. BOTH are Nich VZ series and smaller that what's in there.

C33_PS_caps_I.jpg

Should mention the leads are 0.039" and 0.031" dia.


The 50V (0.79" dia x 1.63" high) has a dielectric disc in the bottom end, where as the 35V (0.71" dia x 1.4" high) has a rubberized plug.

C33_PS_caps_II.jpg


See anything worth commenting on? These caps are for +/-29V lines off the rectifier bridge.

That's what we want around here.... choices!! :beerchug:


-Gregory
 
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Wow Gregory.....another beautiful project....Once again, I really like your attention to detail. :yes:
 
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