> "Pure DI water can get as resistive as 18 Megohm-cm, which is about the
> theoretical limit. This water would be very difficult on fittings and
> metals as it will scavenge ions, which causes migration through the hoses,
> and can plate the metal ions elsewhere. It is very difficult to maintain
> this perfect water in this condition, as it degrades as it strips whatever
> ions it can through the cooling system. You don't want pure DI water, but
> a compromise between 100 kilohm-cm and a few Megohm-cm is appropriate for
> most high voltage systems that need cooling."
John,
Any idea where off-the-shelf distilled water falls in relation to these
figures? I use an Alpha 70V with the better branded water (e.g.,
Zephyrhills). I once purchased "brand X" water off the shelves at Walgreens
and the leakage current indicator went off the scale. Either they had a QC
problem, or tap water was being re-labeled and sold as distilled. I had to
flush the system out a few times, but leakage went back down to about 1 mA @
4KV, a normal value for the amp.
Recently, all the 70V plumbing was replaced (after almost 40 years) and the
overall leakage now is so low that the logic board sometimes interprets it
as having an empty reservoir. The entire plumbing system was replaced with
original JACO Polypropylene parts, still in plentiful supply at industrial
plumbing retailers. Total cost of the rebuild, together with a short
section of new 1/4' copper pipe was about USD $15.00. I have not done
anything to the condenser other than flush it out. I would say that the
cost of ownership with this amp over its 40 year life span has to be at the
extreme low end of the scale, notwithstanding the dearth of available CV
tubes.
Paul, W9AC
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