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Registered Member #543
Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992
tobias wrote ...
Thank you very much PM! It will be my thanks giving reading!
I decided to build the hybrid amp first, just to get familiar with a simple design before going crazy on it.
Already ordered $15 worth of valve and socket and modified layout to match a project box I have here.
About NOS valves: if I find them cheaper than 'new', should I go for the NOS?
New Old Stock
Many 'new old stock' valves offered on ebay are in fact used valves put in a new box.
A genuine 'new old stock' valve of the 1950s and 60s will still have its wrappings inside the box - usually a combination of tissue paper and single thickness cardboard wound round the valve a few times, and often held in place with an elastic band which may have perished with age, but should still be in the box. Always included will be the original guarantee certificate. Look for valves where the paper seal on the box has not been broken.
Genuine NOS Soviet-era valves ALWAYS have a quality control certificate and a data sheet wrapped round the valve and held in place by an elastic band. The paper of the documents is always yellow with age, and may be brittle.
The numbers and letters printed on the glass of a genuine 'new old stock' valve will be sharp and crisp, with no signs of wear.
Types of USED old stock frequently offered as 'new old stock' on ebay:
Valves in new plain white boxes with no wrapping or documents inside the box. (You can buy empty valve boxes on ebay too!).
Valves in genuine old boxes, but in an open condition without wrappings and guarantee inside. These valves are often valves that have been removed from equipment by service engineers because of reduced emission or other faults. It was part of the accounting system of that time for the service engineer to put the bad valve back in the box that the new valve came in, so the managers could see that the engineer had replaced the valve, and not stolen it. They were expensive items. Bad valves like these in genuine boxes may be sold by an innocent person who doesn't know the practice of putting the failed valve back in the box. Many of these valves will work to some extent, and buyers may not notice that the valve has reduced emission or an intermittant fault.
Some valves that are said to be 'tested' by ebay sellers have only had the filament or heater continuity tested.
Always ask an ebay seller why a box has been opened, why it is plain white, why is there no maker's guarantee inside the box, what tests have been performed etc.
Registered Member #3215
Joined: Sun Sept 19 2010, 08:42PM
Location:
Posts: 780
or scavenge some treasures in garage sales, like old radios and the like
best finds are done in university dumps where you can find full valve oscilloscopes which have enough transformer weight to power two hundred or more watts of 350V B+
Registered Member #1956
Joined: Wed Feb 04 2009, 01:22PM
Location: Jersey City
Posts: 172
Shrad, I love flea markets :) Still have to find a good one for electronics on the NYC area that will not charge my weekly wage on the good stuff.
Will ask around for university dumps as well.
Thanks PM for educating me on the NOS subject. If it is to be a used one then I prefer getting the whole piece of used equipment instead of just the valve :)
Registered Member #3215
Joined: Sun Sept 19 2010, 08:42PM
Location:
Posts: 780
we have a flea market here where you could find ten years ago a guy who was selling a huge stock of NOS military grade radio components for PEANUTS, heaps of valves, resistors and capacitors
I still have a look for him each time I go there, but nothing for the last ten years...
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Headphone Tube Amplifier
