[Amps] Cracked Chimney

[Robert Mccormack]

For those on the list that have them, see Bill Orr's "The Radio Handbook" 14th edition, pages 580 through 583 - 'A 4-1000 Pi-Network Amplifier'.   (I'll bet Carl has one)

The glass chimney is not specified and neither is the socket - just a "special air socket".
Note the concave top directing forced air cooling across the anode connector.

Mid-1980s I needed a Coleman lantern chimney and found a replacement in a small hardware store.   The owner offered me his entire obsolete stock of Coleman chimneys (all 4 of them) for NZ$10.   The largest one was identical to the one used in Bill Orr's amp.
(I gave it to a friend for his 4-1000 amp project.)

If I needed that 'Pyrex' chimney now, I would look for those big Coleman lanterns in small-town antique stores before the owners realise that the chimney is worth more than the lantern.<G>

73, Ken ZL1AIH



None these make a really good replacement for a glass chimney for what 
should be obvious reasons.  The glass transmits radiant energy freely.  
Silicone rubber and fiberglass both absorb this energy almost as 
readily. That means they need a wider spacing from the tube envelope and 
more air to keep the new chimney cool.  How well the forced air cools 
the chimney remains to be seen, but fiberglass, silastic rubber (TM) and 
even ceramic used on a glass tube is an entirely different proposition 
compared to using them on external anode/metal tubes.

I think the earlier suggestion make by some one to use cut large glass 
jars such as pickle jars is probably both the best and cheapest approach 
although it does take a bit of practice to make a good one. Done with 
care you can get the straight sides and slight curve in at the top to 
cool the anode seal..

73

Roger (K8RI)