[QuadList] Colortec board 12 capacitor corrosion

[Don Norwood]

Hi Larry:

I've seen a few failures like this, but not this bad!!!

Most of the tantalums that Ampex used in the quad era were mil-spec, hermetically sealed units, and they almost never go bad.  However, these particular ones are wet tantalums which are not hermetically sealed.  Since these are simply filters across the power supply busses, you could replace them with modern-day electrolytics which are small enough these days to fit in the space available.  However, if you insist on the "original" parts, they are still available from suppliers like Avnet or Arrow, but you'll pay $40 to $50 EACH for them.  I did spot a few on eBay for $15/ea....a real deal!!!

I have seen some instances where a board was "shotgunned" and all of the expensive hermetically sealed caps (the ones that almost never fail!!!) were exchanged for cheap electrolytics.  I've never believed in doing that, because I've experienced more failures with the new electrolytics than with the old mil-spec caps.  But in the case of actually needing to replace one of the expensive caps, if we don't have the original part, I'll go with an electrolytic unless the customer requests otherwise.
 
Don Norwood
Digitrak Communications, Inc.
www.digitrakcom.com
  ----- Original Message ----- 
  From: L.E. Odham 






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  Hi all,



  I had a interesting Saturday afternoon repairing board #12 from one of the 1011 colortecs here.

  A couple of the 270 uf mercury electrolytic capacitors had leaked over a period of time and the electrolyte had dissolved every bit of copper clad it came into contact with.

  It wasn't in a machine at this time, thank goodness. It had been sitting quietly on the shelf a number of years as a 'spare'???



  An ugly mess indeed....



  photo attached



  Larry Odham



  Quad Tape Transfer

  www.QUADTAPEXFER.com


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