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Author Topic: U47 Tube Socket Restoration or Replacement?  (Read 3934 times)

afterlifestudios

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Re: U47 Tube Socket Restoration or Replacement?
« Reply #30 on: June 02, 2020, 01:47:59 pm »

Thank you, Kai.  Here’s a photo of one I’ve got here right now.   Aside from the tarnish and potential absence of silver plating and cracks in the Bakelite....  Does the spacing look right?  Images of other sockets seem to have less gap for the pins (tighter fit), but it’s hard to tell...  Any thoughts on the amount of open space here? 

Also, I've never removed a contact, so I don't know what the complete shape of a contact looks like?  Does anyone care to draw the shape of a contact, or post a photo of a removed one? 
(Lame attempt at a diagram of a side profile view below...)

A.)

   /l\                                 
  / l \
    l          or.....
    l
 _/\_
 
B.)

   /l\
 /  l  \
 \_l_/             
    l
 _/\_
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Kai

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Re: U47 Tube Socket Restoration or Replacement?
« Reply #31 on: June 02, 2020, 06:12:46 pm »

Huh, this thing is about to retire.
The plating is gone completely, or is this the tar leftover from dried kontact fluid?

The upper two in the picture look a bit loose, else the bent looks OK.
But that doesn't help, copper or copper plated steel(?) isn't suited as contact material, heated it oxidizes faster than you can say f...

A crack (I don't see it), BTW, could be fixed with epoxy glue (Uhu Plus 300, heat cured) if no other socket is handy.

Get a bunch of sockets from Ebay (they usually go in bigger lots) and select a good one, clean it - mount it - done, forget it.
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klaus

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Re: U47 Tube Socket Restoration or Replacement?
« Reply #32 on: June 02, 2020, 07:32:53 pm »

No Prehs on eBay. The cheap ones that are available have sub-standard plating from the get-go. So you might as well have yours re-plated, as I had mentioned earlier.
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Kai

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Re: U47 Tube Socket Restoration or Replacement?
« Reply #33 on: June 03, 2020, 05:01:39 am »

I had a look through my stock:
8 out of 10 sockets don't look much better than the one pictured.
2 look quite OK.
No Preh in sight here too.

I polished one contact insert to see what it's made from: some kind of bronze.

Then I looked over my tubes: about ~60% of the pins are either nickel plated, very shiny (no silver).
The other 40% are brass, uncorroded with one exception.
I couldn't see any correlation of materials with the embossed or stamped markings.
One is stamped "Wehrmacht" (= pre 1945)  and has nickeled pins.


Conclusion:

• Buying old sockets from Ebay or other sources likely won't bring you any further unless you catch a bigger batch.
  NOS - (NEW Old Stock) - mostly is a lie anyway on Ebay.
  The plating on this at least 65 year old stuff is not made to last that long.

• I have no trust in the Chinese brands. These guys, by my experience, don't have the slightest clue of what materials to use, it just has to be cheap, thin and usually is unsuited for the purpose.


• Option #1 is to follow Klaus' proposal of getting the contacts re-plated - or replate DIY, can't be too hard, the ancient Babylonians 3000 BC already did it.

• Option #2 dismount and polish the contacts with a Dremel/felt disk until the contacting area is perfectly mirror-shiny and smooth.
  Needs to be done anyway before replating.
  If the tube pins are clean and shiny too, this might work for a long time without the silver, if contact force is strong enough.
  Bronze does not easily corrode if kept perfectly clean and dry.


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afterlifestudios

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Re: U47 Tube Socket Restoration or Replacement?
« Reply #34 on: June 03, 2020, 01:29:59 pm »

Thank you gentlemen. 
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DanDan

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Re: U47 Tube Socket Restoration or Replacement?
« Reply #35 on: June 04, 2020, 10:43:00 am »

Indeed, +1
DD
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Dan FitzGerald  MIOA MAES
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Kai

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Re: U47 Tube Socket Restoration or Replacement?
« Reply #36 on: June 09, 2020, 05:53:42 pm »

A friend of my wife is a goldsmith.
She said, galvanic plating these little contacts with any metal - she suggested gold - is common in her job, no problem, and not expensive.

I indeed would vote for gold (or platinum), as the tube contacts seem to be either nickel or brass, the combination works well and does not suffer from contact-corrosion.
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DanDan

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Re: U47 Tube Socket Restoration or Replacement?
« Reply #37 on: June 10, 2020, 07:56:26 pm »

Hi Kai, more good info tx.  Funnily I was just now logging in to PM you a question to clarify something, but I guess it is probably of public interest.
You mentioned not to mix solders. What happens if one does?
Also, I have been using Sennheiser HD 480s for decades. They cause great happiness in Recording Studios.  The continuity fails so I have been buying new drivers, new cables, new pads when the foam starts to crumble.
I have three sets left and I was about to butcher them, try to solder directly to the drivers...... But another comment here came to mind, contact pressure. Optivisor on,  I discovered that the tiny contacts were transverse springs rather than similar to valve sockets. A little precision bending has rebirthed them.

Everyone:-
I am getting in some cleaning fluids for the workbench. Caig Deoxit vs Kontakt 60?
67s-
No response from Sennheiser UK (Neumann) so I plan to investigate if there is any Kontakt 2000 residue in the U67 sockets.
Any thoughts on Interdentals for this job? Socket upside down to drain the fluid of course.
Rather than brake cleaner of unknown brand and composition, is there a truly great proprietary electronic cleaner?

DD
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Dan FitzGerald  MIOA MAES
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Kai

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Re: U47 Tube Socket Restoration or Replacement?
« Reply #38 on: June 11, 2020, 03:20:16 am »

Solders:
Stay with 60/40 tin/lead ELECTRONICS solder with collophonium flux, the whole mic is built that way.
The 98/2% tin/silver (euphemistically so called "silver solder") is mechanically less reliable, harder to work with, and the flux of some needs to be washed away after - impossible to do in the mic.

The contact springs in some Sennheiser headphones' series are known to fail.
Sennheiser offers (offered?) improved replacements.
Soldering the cable is not a real option.
Beware not to break the very thin driver leads, very hard to fix.


For cleaning the tube socket it has to be removed, and the contacs have to be taken out.
Quite straight-forward to do.
Poking in the contacts with whatever leaves the job half undone at best.

Most deoxi works on sole metal contacts.
A bit of rub is needed anyway.
Kontakt 60 is proven.


There are various expensive "washers" available, like Kontakt Chemie "Tuner Spray".
For me brake cleaner always did the job, I use this one:

https://smile.amazon.de/Brake-Cleaner-Aerosol-500ml-08901087/dp/B07NJ9SNLS/ref=sr_1_5?__mk_de_DE=ÅMÅŽÕÑ&dchild=1&keywords=Würth%2BBremsenreiniger&qid=1591860657&sr=8-5&th=1

It's cheap, no need to use it sparse, so it really "washes".
It's pure Naphtha as far as I know.

Washers have to fit to what is to be removed.
In this case Kontakt 60 to desoxy and dissolve, then brake cleaner to degrease/remove the Kontakt 60 is what is needed.


To make it clear: nothing senseful can be done with the socket inplace, it has to be taken out of the mic.
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DanDan

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Re: U47 Tube Socket Restoration or Replacement?
« Reply #39 on: June 11, 2020, 11:35:43 am »

Thanks for the specific name of brake cleaner, I will invest in some K60 also.

Again sorry my bad,  there is a bit of 'bleed' between topics. I am doing nothing about the 47 for the moment. Until Andreas gets to revitalise the Valve and assess the capsule there seems to be no point in treating unidentified symptoms. I have cured most of the noise for now with simple dry cotton bud cleaning.  I have a German friend looking for a Preh.

There is a spread of opinion about the absolute necessity for that brand, but I am sticking with Klaus's advice. I intend replacing the U67 sockets, on the basis that they definitely got several small doses of Kontakt 2000 from valve pins deliberately, mistakenly, left wet.

Neumann/Sennheiser are not responding, so I will try an upside down cleaning using Interdentals and Isopropyl. No fluid will get up into the mic.


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Dan FitzGerald  MIOA MAES
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Kai

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Re: U47 Tube Socket Restoration or Replacement?
« Reply #40 on: June 12, 2020, 05:15:41 am »

RE: Naphta:
I just quoted the manufacturer of the brake cleaner.
In EU manufacturers are forced to tell what is used in their products.

Naphtha is a mix of lighter hydrocarbons, mainly C5 and C6, distilled from crude oil.
If something is used for cleaning you want to make sure that it does not do any damage.
Despite alcohols and other solvents, pure Benzin does leave most materials alone.
In my experience it never did any harm to anything I used it on, for degrease.
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DanDan

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Re: U47 Tube Socket Restoration or Replacement?
« Reply #41 on: June 12, 2020, 01:36:01 pm »

I went with the Kontakt cleaner recommended by them.
As well as grease it claims to remove oxides and sulphide etc.
https://ie.rs-online.com/web/p/contact-cleaners/0405165/

Kai, I sent you a Private Message.
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Dan FitzGerald  MIOA MAES
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DanDan

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Re: U47 Tube Socket Restoration or Replacement?
« Reply #42 on: July 06, 2020, 01:52:49 pm »

Well I set about the cleaning the two 67 sockets and valve pins last night. The instructions on the Kontakt 60 are minimal. How long should one leave a Deox on Glass Valve Pins?
I noticed my 90's re-issue U67 has what looks like a ceramic base and silver plated, or silver, pins. The other, an original West Germany one, has gold plated pins and what looks like a Teflon? base.
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Dan FitzGerald  MIOA MAES
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DanDan

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Re: U47 Tube Socket Restoration or Replacement?
« Reply #43 on: March 01, 2021, 08:18:11 pm »

So, finally back to the Original Topic proper. I have carefully extracted the Tele VF14 which looks to be honest, new. While unsoldering the Preh two of the wires popped off cold. I have cleaned the Preh with 60 and WL and Iso. I haven't done a long Deox soak because I am thinking of getting them silver plated.
I am a little nervous of straightening those bronze parts and then bending them again. Encouraging words please!  Also any tips on removal and reinstall. The VF pins look very shiny, silvery. When I go to my plater, I would chose gold or silver I presume. Which do ye recommend?
Warm thanks.
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Dan FitzGerald  MIOA MAES
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klaus

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Re: U47 Tube Socket Restoration or Replacement?
« Reply #44 on: March 01, 2021, 08:54:40 pm »

Cold solder joints are not uncommon on VF14 tube socket connections. Push and press each contact hard with a small screwdriver, or, to be safe, resolder all socket connections.

I would only replate the socket contacts if, after thorough wiping with Caig Pro Gold, you experience discharge sounds.
Try that first.

There is no harm in straightening the bent-over ends of each contact, so that they pass through the plastic slot in the plastic socket. Re-bending them after they have been plated is harmless. I've done it hundreds of times with not a single break.

I caution against gold plating, for two reasons:

1. While corrosion resistant, gold is a worse conductor than silver

2. Dissimilar metals (silver/nickel plated tube pins and gold socket contacts) accelerate corrosion.
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Klaus Heyne
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