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Old 9th Oct 2020, 3:13 pm   #1
DonaldStott
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Default Restuffing Dual Electrolytic Can Capacitor

I know that this topic has been covered in numerous Threads previously but I found the experience both interesting and educational as I worked through the various stages of this Dual Electrolytic Can Capacitor restuffing, so I thought I would share these with the Forum.

Bit of background - I picked up this Bush DAC10 cheaply but didn't expect that almost every section would need replaced, rebuilt or refashioned in some way, especially the wiring - click here More BUSH DAC10 Woes! As for the large can holding the 16μF smoothing and 32μF reservoir capacitors, well that was simply missing and a more recent dual can (32μF + 32μF) had been substituted. This was only held in place by its wiring and was not secured to the chassis. In addition the dual can caps were measuring 45μF and 38μF which seemed well above the required operating characteristics so the decision was made to change these.

It would have been possible to obtain a modern Dual Electrolytic Can Capacitor (16μF + 32μF), for example, from the BVWS, but as I had another identical can from another set I thought that I would have a go at restuffing that with modern electrolytics which I already had in my supplies, something I'd never tried before! The dual can retaining clip was still in situ on the chassis and fitted the replacement perfectly, so here we go...

Stage 1 - Clearing out old can.

First thing I needed to do was to work out how to get into the old can to remove its contents. The replacement would have its terminals visible above the chassis so the option of snipping round the base and peeling back the metal was not desirable. I decided to use a Junior Hacksaw to remove the base and leave a clean edge.

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From there it was a bit of a struggle to extricate the innards but they eventually succumbed to my persuasions. A lot of crud was scraped from the inside of the can but much more remained along with lots of wax :-

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As there is limit of five images per Post I am aware that I have several more Stages and many images I can share if members of the Forum are interested and the Moderators are happy for me to proceed??
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Last edited by DonaldStott; 9th Oct 2020 at 3:16 pm. Reason: Typo
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Old 9th Oct 2020, 3:29 pm   #2
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Default Re: Restuffing Dual Electrolytic Can Capacitor

If the mods are happy please continue, so far I have replaced electolytics with modern equivalents as they would be out of sight but have kept the old ones for re-stuffing when I get that magical round tuit.
I for one would be interested in seeing the step by step process.

Peter
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Old 9th Oct 2020, 8:00 pm   #3
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Default Re: Restuffing Dual Electrolytic Can Capacitor

Of course. No two restorations are the same. It would be boring (pun incidental) if they were.
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Old 10th Oct 2020, 12:00 pm   #4
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Default Re: Restuffing Dual Electrolytic Can Capacitor

Stage 2 - Disassembly of end cap

Once the end cap was cut from the can it was clear that this had been sealed by some form of pitch type material which had set rock hard. This all had to be removed to free the end ring and to get access to the other ring of metal with the tabs used to secure the can to the chassis - used when the capacitor connections lie underneath the chassis. At this stage it was the intention to re-use the Paxolin disc if possible but the tab ring wasn't required and could be discarded.

Took quite some time with a fine metal pick to remove all this material from the end cap:-

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Eventually I managed to disassemble the end cap to leave us with the three components already mentioned - the end ring, the tab ring and the Paxolin disc with the connectors: -

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Close examination of the Paxolin disc showed that it was in an advanced state of disintegration and I decided that it probably wouldn't withstand drilling and fitting of new connectors. So that left us with just the can and the end ring: -

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Although most of the crud had been scraped out from the inside of the can there was still a waxy residue with embedded bits. What I did then was to stand the can upside down on a scrap piece if wood and then used my hot air gun to heat the can and melt the wax which flowed out onto the scrap wood. Any remaining wax residue was removed using cellulose thinners which left us with a nice clean can, ready for the next stages!
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Old 10th Oct 2020, 7:55 pm   #5
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Default Re: Restuffing Dual Electrolytic Can Capacitor

Quote:
Originally Posted by AC/HL View Post
Of course. No two restorations are the same. It would be boring (pun incidental) if they were.
I don't get it.

Interesting process, Donald. Clear photos, too.
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Old 10th Oct 2020, 8:27 pm   #6
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Default Re: Restuffing Dual Electrolytic Can Capacitor

https://www.vintage-radio.net/forum/...9&postcount=18
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Old 11th Oct 2020, 1:29 am   #7
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Default Re: Restuffing Dual Electrolytic Can Capacitor

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Thanks for the recap

I'll get my coat.

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Old 11th Oct 2020, 12:12 pm   #8
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Default Re: Restuffing Dual Electrolytic Can Capacitor

Stage 3 - Make a Paxolin disc!

In Stage 2 above I determined that the existing Paxolin disc from the dual can probably wouldn't withstand drilling and fitting of new connectors so this gave me no option but to look online for such a disc or to fabricate one myself. I searched the Forum for any links to online sources but none were forthcoming, as expected, and similar online searches using Google were also unsuccessful.

So fabricating a new Paxolin disc it was then ...!

During my search of this Forum I did come across this Thread which proved very helpful - click here Paxolin Disks

I started off by cutting a square piece of Paxolin and used the existing disc as a template. With my Junior Hacksaw I repeatedly removed the corners until I was left with something like a circle although slightly bigger than the original disc.

In the absence of any proper workshop equipment as recommended in the above Thread e.g. a wood turning lathe, I took inspiration from the advice from crackle (Mike) in Post #7 of that Thread. The required disc is about 35mm in diameter so that it fits over the end of the can but is held in place by the end ring shown in the last picture of my Post #4 above. I used my hot glue gun to attach the new, slightly oversized but almost circular disc to the end of a piece of 35mm oak dowel I had from another Project!

HEALTH AND SAFETY - Please look away now!

Outside in the garden I clamped my hand sander to my Workmate but upside down with the sandpaper face showing, switched it on and gradually introduced my dowel with disc attached while rotating it slowly. I used a 120 grit sandpaper and gently let the weight of the dowel do the work until the disc matched the circumference of the dowel almost exactly - no need to be perfect as the new disc would be held in place under the end ring.

And here is the result: -

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The new disc was just heated up and slid off the dowel quite easily - any residual glue just peeled off. The acid test was whether or not the new disc would indeed fit inside the end ring, be held in place on the end of the can and be fit for purpose: -

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So there we have it - a new Paxolin disc in place and all ready for some new connectors which will be covered in the next Stage!


NOTE: There is some debate over whether disc or disk is the correct spelling - I have used disc throughout but see here Spelling of disc
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Old 11th Oct 2020, 3:11 pm   #9
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Default Re: Restuffing Dual Electrolytic Can Capacitor

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I knew it was a charged remark...

I think you've got my coat, Catkins.
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Old 11th Oct 2020, 4:31 pm   #10
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Stage 3 - Make a Paxolin disc!
That looks a good technique, Donald. Making a new circular acrylic glass for my Ferrograph tape counter, I mounted it on a drill and filed down the edge as it turned. Of course, that had a hole in the middle so was easily chucked by mounting a machine screw through the middle. I imagine a glued hub would work too. The only difficulty was keeping the edge cool enough so as not to melt.
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Old 12th Oct 2020, 2:25 pm   #11
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Default Re: Restuffing Dual Electrolytic Can Capacitor

Hi. I was interested to read about your capacitor re-stuffing. The can on my Bush DAC10 has also developed faults (leaky), and also the cans on other radios seemed to have followed similar fates. I knew that the DAC10 radio did work up to last year.
Someone told me that you could mount a two bit tag strip, one to the terminal of the faulty capacitor as an anchor point, the second tag strip terminal could be used to attach the (+) lead of the new capacitor to. The (-) terminal of the new capacitor can be connected to chassis, of course. All this without opening the can (assuming that you wanted to achieve success in lesser time). It depends on if you consider it to be a "bodge" or a reasonable attempt to make your radio work.
I will have to try and stock up on small 450v electrolytic capacitors since my local stockists have gone. Probably the supplier in Watford can help me?
regards
Mike
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Old 12th Oct 2020, 3:51 pm   #12
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Default Re: Restuffing Dual Electrolytic Can Capacitor

Thanks to UB and Mike for your responses - I was becoming a bit concerned about the lack of feedback.

@Uncle Bulgaria - I had contemplated using the technique you suggest but felt that my dowel approach gave me greater control and didn't leave me with an annoying hole in the middle. At all times I"m eager to stress that I'm not putting forward the methods I used as 'best practice' in any way! I'm simply describing the approach I took to the challenges of restuffing a dual electrolytic can capacitor.

@telstar - I've now replaced the smoothing and reservoir capacitors in several valve radios and 1960's record turntables. On most occasions it's been possible to connect the replacements to a new tag strip mounted under the chassis and out of sight - often leaving the original can in place. This time round I thought I'd have a go at restuffing as I had a spare can from another set and, partly, to see see how difficult it could be? In addition the Bush DAC10 has the large tuning unit under the chassis so not much space there!

The 450V replacement caps I used were Rubycon Electrolytic Capacitor, Miniatures from Farnell as recommended by Forum member David G4EBT. Three of these will fit inside a standard Bush can although only two were required for the current restuffing - see the next Stage coming up soon!
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Old 12th Oct 2020, 4:05 pm   #13
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Default Re: Restuffing Dual Electrolytic Can Capacitor

Excellent descriptions and photos Donald.

I have never done restuffing and generally personally would not, as to me seems like quite a bit of work, especially when the cans normally are not visible.

However from your and other restuffing threads I have read, I may give it a go sometime.

David
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Old 12th Oct 2020, 5:53 pm   #14
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Default Re: Restuffing Dual Electrolytic Can Capacitor

Quote:
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Someone told me that you could mount a two bit tag strip, one to the terminal of the faulty capacitor as an anchor point, the second tag strip terminal could be used to attach the (+) lead of the new capacitor to. The (-) terminal of the new capacitor can be connected to chassis, of course. All this without opening the can (assuming that you wanted to achieve success in lesser time). It depends on if you consider it to be a "bodge" or a reasonable attempt to make your radio work.

Mike
Thats basically what I did when restoring my Mullard High Speed Valve Tester, it leaves the original capacitors in place in case a future owner wants to re-stuff them.

Peter
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Old 13th Oct 2020, 5:01 pm   #15
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Default Re: Restuffing Dual Electrolytic Can Capacitor

Stage 4 - Connectors and Capacitors

Having successfully fabricated a new Paxolin disc I drilled equidistant holes for three new connectors using my Dremel on its drill stand - other rotary tools are available.

Coloured dots were used to identify the +ve connections for the smoothing (YELLOW) and reservoir (RED) capacitors and and for the -ve common connections (GREEN) - these were stuck to the disc prior to drilling. Solder tags were attached to each side of the disc using pop rivets for the new internal and external connections: -

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Just to be sure that everything was still ok I had a trial fit of the new disk with connectors on the can with the end ring: -

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Although the original values were 16μF for the smoothing capacitor and 32μF for the reservoir capacitor I substituted 15μF 450V and 33μF 450V Rubycon Electrolytic Capacitor, Miniatures from Farnell - other suppliers are available.

My hot glue gun was then used to stick the two caps together and the -ve common leads were twisted together. Exposed leads were covered with heat shrink, appropriately coloured (RED YELLOW GREEN), to prevent any risk of shorting and to ensure the correct connections were made: -

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The new electrolytic capacitors were then soldered to the connectors on the new Paxolin disc: -

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Old 13th Oct 2020, 5:22 pm   #16
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Default Re: Restuffing Dual Electrolytic Can Capacitor

Really nice job. May I suggest drilling a 3mm or so hole in the base so if the replacement capacitors let go at some point then it'll be less interesting
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Old 13th Oct 2020, 6:45 pm   #17
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Default Re: Restuffing Dual Electrolytic Can Capacitor

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Really nice job. May I suggest drilling a 3mm or so hole in the base so if the replacement capacitors let go at some point then it'll be less interesting
I'd thought about doing something similar to allow the dissipation of any heat to some extent - the new disc and existing end ring will be sealed onto the can with epoxy.

I've dealt with the aftermath of capacitors letting go in a couple of valve radios so any work at this stage to make it "less interesting" is certainly worthwhile!
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Old 15th Oct 2020, 4:14 pm   #18
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Default Re: Restuffing Dual Electrolytic Can Capacitor

Nicely done but an observation, I hope you do not mind.

You do not need the tags inside maybe just a washer. Drill three 1mm holes through the disc immediately next to and behind the front tags and pass the leads through, then loop them round the base of the tags and solder hard against the disc. Once you solder the wires / components to the tags you will not notice the loops.

No chance then of the rivet loosening or suffering aluminium to solder resistance over time.

Alan
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Old 16th Oct 2020, 11:40 am   #19
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Default Re: Restuffing Dual Electrolytic Can Capacitor

Thanks Alan - that's a variation I hadn't thought of, well done and nice job!

In my restuffing I used stainless steel rivets, not aluminium which forms an electrically resistant oxide surface in electrical connections.

As I mentioned in a previous Post " ... I'm not putting forward the methods I used as 'best practice' in any way! I'm simply describing the approach I took to the challenges of restuffing a dual electrolytic can capacitor." The more options we have then so much the better!
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Old 16th Oct 2020, 12:12 pm   #20
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Default Re: Restuffing Dual Electrolytic Can Capacitor

Stage 5 - Labelling

For the benefit of any future restorer (!) I thought it would be important to highlight that the contents of the can had been changed and differed from the original text on the side. I tried various solvents to remove this original text but nothing seemed to shift it.

The original can was a DUBILIER and I needed to update the text to specify the new can contents and connections:-

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I decided to use water-slide decal paper to fabricate a new label and this was printed off on my inkjet printer, carefully following the instructions:-

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(NOTE: There is an amusing coda to this part of the exercise which I'll Post later, warts and all!)

Everything was allowed to dry overnight and the can and label were also given a finishing coat of clear metal lacquer. The can was put back in place on the chassis, secured with the retaining clip and the connecting wires to the three terminals were soldered:-

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