On 4/21/2013 9:13 PM, Phil Allison wrote:
"Trevor Wilson"

** Here is a pretty good pic of the insides of a 545B.

http://www.barrytech.com/tektronix/v...k545bright.jpg

The AC tranny looks like it *might* be 500VA - but I expect Tek would
use a
conservatively rated unit with a low temp rise.

If the OP would care to measure the primary resistance - I can say for
sure.

**I found my 545A manual.

Power consumption is rated at 500 Watts. Weight is 65 pounds.

Fuse ratings:

6.25 Amp Slo-blo 3AG for 117VAC 50Hz
6 Amp fast blo 3AG for 117VAC 60Hz
3 Amp fast blo 3AG for 234VAC 60Hz
3 Amp slo-blo 3AG for 234VAC 50Hz


** Hmmmmm.....

Those numbers make me think the AC tranny is quite conservatively rated for
voltage and frequency.

Doing so, reduces the severity of inrush surges quite a bit.

BTW 1:

If you operate a 240V rated tranny on 120V - there is barely ANY inrush
surge at all.

( Electro caps in the PSU not withstanding. )

BTW 2:

The main source of inrush surge with tube gear is often due to all the tube
heaters being cold at switch on - particularly if the rectifiers are
vacuum tubes. The buggers take quite a time to warm up and increase in
resistance too.

But the 545B uses selenium diodes - right?


**I doubt it. The CRO does use a time delay at switch-on.


--
Trevor Wilson www.rageaudio.com.au