Steve,
That kind of makes you think the probe is working. You can check the
normality of the NAOH with potassium Acid Phthalate and
Phenolphthalein, maybe it's just off...

On the tube amps, my brother is a guitarist and loves tube amps too.
I used to work on a pretty big one years ago, it was 250,000 VA in,
180,000 out. The outputs were about 5 feet high and water cooled.
(It was a Ling amp, we used it to driver shakers in a vibration lab.)
Now that was a cool amp. Not too portable though,it's input power was
3 phase 4160VAC and it was around 20 ft long...

One of the guys would play music through it on holidays. When we
shook really big 'stuff' pretty hard the vibration went through the
bedrock and into buildings several hundred feet away.

It was impressive. And it wasn't the bigest one Ling made... )

Joe

:^) - bottlehead forever!
>
> Steve in Vancouver