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Author Topic: U47 Tube Socket Restoration or Replacement?  (Read 10574 times)

DanDan

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Re: U47 Tube Socket Restoration or Replacement?
« Reply #45 on: March 02, 2021, 05:34:20 PM »

You are very generous Klaus. Thank you.
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Dan FitzGerald  MIOA MAES
www.irishacoustics.com
www.soundsound.ie

DanDan

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Re: U47 Tube Socket Restoration or Replacement?
« Reply #46 on: March 12, 2021, 03:29:25 PM »

Well, with respect to all the generous help here, a progress report.  A couple of hours with Kontakt 60. An interdental brush. Good wash with Kontakt WL and finally Isopropyl. 
The light temp makes this a little off, it is quite silvery in reality.
The valve looks as new. Amazing really.
I think I will pursue a bit more cleaning by taking off the little circuits etc. Good to check the wire soldering, given that two came away from the Preh when I was gently removing it.
A last question please. The Head basket and body tube are off obviously.  Good time for some sort of Wash, or Bath?  Washing up Liquid? Isopropyl?
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Dan FitzGerald  MIOA MAES
www.irishacoustics.com
www.soundsound.ie

klaus

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Re: U47 Tube Socket Restoration or Replacement?
« Reply #47 on: March 12, 2021, 09:03:53 PM »

Every of your cleaning steps is fine, except the last one: I would not leave the contacts bone dry and unprotected, but coat the contacts with an anti-oxidization fluid. I use Caig Pro Gold for that.

As to cleaning metal parts of a mic, I wrote a sticky on that: https://repforums.prosoundweb.com/index.php/topic,37300.0.html
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Klaus Heyne
German Masterworks®
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DanDan

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Re: U47 Tube Socket Restoration or Replacement?
« Reply #48 on: March 13, 2021, 01:54:53 PM »

Hmm, US products can be difficult here. I have Kontakt Gold. To be honest I am pretty convinced my worst problems were appalling soldering and a build up of black superfine dust like you would see around an ioniser.
I am clearing the workshop of another restore (1176) so the great rebuild is imminent. Wish me luck.  I remember that sticky well, but it is the head basket I am focussed on. To be honest, it doesn't appear dirty at all. But as it is apart, I am inclined to give it a soak in water and washing up liquid. Unless there is any danger of staining or things I don't know.
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Dan FitzGerald  MIOA MAES
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www.soundsound.ie

afterlifestudios

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Re: U47 Tube Socket Restoration or Replacement?
« Reply #49 on: March 25, 2021, 09:59:20 PM »

How's it working out DanDan?  Did your restoration of the socket clear up the noise problems?
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afterlifestudios

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Re: U47 Tube Socket Restoration or Replacement?
« Reply #50 on: April 02, 2021, 02:44:59 PM »

After some unsuccessful attempts at restoring one of my original Preh sockets, I picked up a replacement socket (and suspension assembly) from Flea.  Nickel plating.  Here's a couple pics.  This way I can be without the Preh and still (hopefully) have a working mic while I take subsequent steps (re-plating the silver contacts) on the Preh.  Just thought I'd post in case anyone else is in the same boat.
* No affiliation with Flea or anything.  In fact, it's the only time I've ever dealt with them.

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klaus

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Re: U47 Tube Socket Restoration or Replacement?
« Reply #51 on: April 02, 2021, 04:01:29 PM »

Can you share the cost?
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Klaus Heyne
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DanDan

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Re: U47 Tube Socket Restoration or Replacement?
« Reply #52 on: April 02, 2021, 05:32:48 PM »

Going well, but extremely slowly. Which I don't mind at all. I am pretty happy with my Preh which you can see in an earlier post.  Kontakt 60 soak, Kontakt WL wash, IPA wash. Tx Kia.
Cleaned the body and basket with warm water and washing up liquid. Tx K.  It looks lovely now, still obviously old, but now obviously cared for. I have stalled for the moment as I feel a need to replace the two high value Resistors. The 100M has drifted to 133M, the 60M has gone to 125M.
It is proving impossible to find a 60M or even combinations to achieve that value.
I will keep the originals in case of a future sale, but for now I am looking for performance. Best shot so far seems to be these. https://ie.rs-online.com/web/p/through-hole-fixed-resistors/8492750/ But I will have to accept  10+47+  57M and a different composition for the grid R.
Tele USA are also willing to supply a nice looking gold plated socket with suspension for 149 bucks.
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Dan FitzGerald  MIOA MAES
www.irishacoustics.com
www.soundsound.ie

RadarDoug2

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Re: U47 Tube Socket Restoration or Replacement?
« Reply #53 on: April 02, 2021, 05:46:14 PM »

Have another search at RS, lots of high ohm resistors in different styles. You can get a single resistor at 68M. and resistors up into the Gigohm.
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DanDan

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Re: U47 Tube Socket Restoration or Replacement?
« Reply #54 on: April 02, 2021, 06:13:29 PM »

LOL I have spent hours on there. Trying to stick to one brand, size, and appearance. Just when you think you have it....... next delivery june!  I have spent time on Farnell and Digikey also.....
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Dan FitzGerald  MIOA MAES
www.irishacoustics.com
www.soundsound.ie

afterlifestudios

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Re: U47 Tube Socket Restoration or Replacement?
« Reply #55 on: April 02, 2021, 10:08:21 PM »

Can you share the cost?

Well, it was 180 Euros for TWO of the socket assemblies including express shipping to Canada, so I think they were 65 Euro each before shipping?
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afterlifestudios

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Re: U47 Tube Socket Restoration or Replacement?
« Reply #56 on: April 02, 2021, 10:10:45 PM »

Going well, but extremely slowly. Which I don't mind at all. I am pretty happy with my Preh which you can see in an earlier post.  Kontakt 60 soak, Kontakt WL wash, IPA wash. Tx Kia.
Cleaned the body and basket with warm water and washing up liquid. Tx K.  It looks lovely now, still obviously old, but now obviously cared for. I have stalled for the moment as I feel a need to replace the two high value Resistors. The 100M has drifted to 133M, the 60M has gone to 125M.
It is proving impossible to find a 60M or even combinations to achieve that value.
I will keep the originals in case of a future sale, but for now I am looking for performance. Best shot so far seems to be these. https://ie.rs-online.com/web/p/through-hole-fixed-resistors/8492750/ But I will have to accept  10+47+  57M and a different composition for the grid R.
Tele USA are also willing to supply a nice looking gold plated socket with suspension for 149 bucks.

Very cool.  So, did it clear up the noise issues you were having?  Or is the mic still in pieces?
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DanDan

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Re: U47 Tube Socket Restoration or Replacement?
« Reply #57 on: April 03, 2021, 06:22:40 PM »

LOL, listen I may be slow, but at least I'm expensive.......
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Dan FitzGerald  MIOA MAES
www.irishacoustics.com
www.soundsound.ie

afterlifestudios

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Re: U47 Tube Socket Restoration or Replacement?
« Reply #58 on: April 04, 2021, 12:53:41 AM »

LOL, listen I may be slow, but at least I'm expensive.......

Haha.  OK.  I'll be patient.  Just super curious if it was the socket, and if your restoration is successful.  I'll be popping my new Flea socket in when this session wraps...
Best of luck.
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DanDan

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Re: U47 Tube Socket Restoration or Replacement?
« Reply #59 on: July 14, 2023, 07:50:47 PM »

I am back on the horse. Long story but.....  I have resumed my U47 cleaning project.
There is a lot of fine black dust, or even mould?  Originally it was just high level noise, and removing some of that dust with cotton buds, no liquid,  was enough to drop the noise way down. So I intend cleaning all the detachable bits in a small  Ultrasonic bath.
The high Rs are 130M and 68M so I have replacements. I will talk to a jeweller re silver plating next week.
One of my advisors is worried about the insulation resistance of the Preh valve socket  material. He tests at High Voltage and wants to see Gigohms.  I have a cheap LCR meter which is showing nothing on the 2000M range.  He thinks it is Bakelite?  Is that true or is it something exotic with very good insulation that doesn't fail?
DD
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Dan FitzGerald  MIOA MAES
www.irishacoustics.com
www.soundsound.ie
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