The PHILCO Phorum
MERSHON condenser rebuild - Printable Version

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MERSHON condenser rebuild - Tubesforme - 07-30-2016

Hello,
I have read several articles regarding re-stuffing the MERSHON copper condensers. I have tried to remove the top cap on a couple of old ones, before I do the two that I need. I was not able to get the tops off without either denting or scratching the can, using a screw driver. I was also not able to loosen the tops using a small piece of wood with the hammer. I also read that you can cut them open, but I don't care to do that. I would like to know how some of you open them. How do you hold them while tapping off the top cap? How do you tap off the top cap without scratching or denting the top or can? They polished up beautifully with Brass Polish and they do set the radio chassis off. I do not care to install the replacement capacitors under the chassis. Any good ideas? Thanks to anyone who has an answer.

RE: MERSHON condenser rebuild - Ron Ramirez - 07-30-2016

http://philcoradio.com/phorum/showthread.php?tid=15041&pid=111855#pid111855

RE: MERSHON condenser rebuild - Tubesforme - 07-31-2016

Thanks Ron I think that I might be better off seeing if I can find someone who is willing to rebuild them for me. I don't have a shop anymore and the dining room table just isn't enough for this type of work.

RE: MERSHON condenser rebuild - Tubesforme - 08-01-2016

Bobs idea worked great, However I hit a dead end and have emailed him. I was able to remove the insides very easily, using Bobs method. However I am unable to remove the rod to which the aluminum was attached. There is a nut mounted, on the very bottom, inside the potting material (the threaded part) and while I cam wiggle the post back and forth a little, even after soaking the bottom nut with WD40, I simply can't turn the post out and am afraid I will bread the threaded part that holds the capacitor to the chassis.  There is no way to hold the nut that is molded inside of the mounting.  I have threaded the nut that mounts the parts to the capacitor, all the way down to the one molded inside of the assemble and can put it on and take it off so the threads must be good on the rod assembly and nut. Thanks, Michael

RE: MERSHON condenser rebuild - klondike98 - 08-01-2016

It was not my idea...I got the advice from Russ (Phlogiston), I just posted what I did.   I'll check for your email.

update: I don't see any email and it should have arrived by now I think.  try again or PM me.  Some pictures would help.  The accordian looking piece that is attached to the aluminum threaded rod on the Sprague caps all came out easily together.  I recall I may have had to turn it but I did not notice a nut embedded in the black bakelite/rubber base.  If you can not get the threaded rod out, is there enough residual metal above the bakelite/rubber base to use as a lug to attach wires to?  You can't solder aluminum but you can drill a hole and then use a nut, washer and small machine screw to fasten wires to the metal.  I'm just thinking on the page here, without seeing what's going on.

RE: MERSHON condenser rebuild - Phlogiston - 08-02-2016

(08-01-2016, 06:16 PM)Tubesforme Wrote:  I was able to remove the insides very easily, using Bobs method. However I am unable to remove the rod to which the aluminum was attached.

Use a socket to support the plastic threaded base - a deep 3/8" drive 5/8' is about right. This allows the threaded rod to go through the socket driver hole. Use a hammer to drive the rod out of the base. Use some WD-40. I have taken a lot of these out of the base this way.

RE: MERSHON condenser rebuild - Tubesforme - 08-02-2016

Thanks Ron, I am going to pick up a socket and try that. I had thought about drilling a hole in the aluminum and using a small bolt, but like your idea better. By the way, the inside of the electrolytic that I opened, does not have the accordion type cap, it has the spiral wound type. It was very easy to remove the inside of the roll was held onto the aluminum rod with two rivets. Michael

RE: MERSHON condenser rebuild - Phlogiston - 08-02-2016

Russ - Ron is the other guy Icon_lol

RE: MERSHON condenser rebuild - Ron Ramirez - 08-02-2016

Yes, let's give credit where credit is due - to Russ for the idea, and to Bob for illustrating the technique. All I did was to post a link to Bob's thread showing how he did this work.

Russ, I appreciate your idea and I am going to try and restuff some Mershons using this method sometime in the near future. Icon_thumbup

RE: MERSHON condenser rebuild - Phlogiston - 08-03-2016

Keep in mind that none of this - or very little applies to the copper Mershons. This is really about the Sprague caps that are nickel plated.

Most, but not all of the copper Mershons have either a pressed on cap or a screw base (no screw basses in Philcos). These are dealt with differently.

I would also add that my method for grounding is to attach to the can its self. Sometimes this is almost necessary when stuffing a 10 or 15uf film cap into the tube. In the majority of cases there is either a hole, that you made under the cap (pressed on top cap) or a vent hole that makes for a nice spot to solder a ground.

Here is another little tip if grounding the can. There is only limited torque that can be applied to a glued in base. This may make chassis contact questionable. In those cases that use the base/ground ring/contact, I make a small solder joint to the can and that ground ring. These were used in some Philcos. I also used this in the Spragues that I installed into the Strat. An intermittent ground will cause all kinds of noise to say the least.

RE: MERSHON condenser rebuild - Ron Ramirez - 08-03-2016

Well,

I attempted to remove the top cap from a Mershon once.

After destroying it in the process...

I will never try that again. I'll grind at the bottom of the capacitor next time, as Bob did with the Sprague...

RE: MERSHON condenser rebuild - KCMike - 08-03-2016

  Before reading the how to rebuild mershon caps. I tried heating the top of cap to remove it.
It resulted in blue flame and black smoke emitting from the small vent holes. Icon_e_surprised  Luckily it did not explode.

RE: MERSHON condenser rebuild - Ron Ramirez - 08-03-2016

Mike

That just conjures up images of Beavis and Butt-head...

Uh, huh-huhuhuhuh, that was cool.

[Image: http://www.taurusarmed.net/forums/attachments/firing-line/110717-amazing-slow-motion-49849361.jpg]

RE: MERSHON condenser rebuild - KCMike - 08-03-2016

Icon_lol  Yea it was cool looking. But won't do that again.

RE: MERSHON condenser rebuild - morzh - 08-03-2016

I am pretty sure whoever thought up those vent holes probably had a good reason to do so Icon_lol