Inrush limiting question - Tek 603 refurb
I've been working on a Tek 603 for a few months, starting with recapping
and replacing a transistor to resolve a Z amp problem.
Today I was able to complete X and Y gain adjustment and the display
should be basically usable.
However, on a previous power on, after sitting on the bench for a couple
of months, it blew the 215V fuse F830. I replaced the fuse and brought
it up on Variac and it hasn't had any problems since. So now I'm
wondering if it's a good idea to fit a thermistor as an inrush limiter
to be more gentle on the 50 year old supplies.
Is this a nutty idea? I'm thinking it should be easy to do taking
advantage of existing AC jumpers on the rectifier board.
An NTC inrush limiting thermistor should work just fine. There are a lot of kinds, so choose properly. It should stay hot with the normal load, so be sure to provide good clearance around it.
On 2020-11-10 9:54 p.m., Ed Breya via groups.io wrote:
An NTC inrush limiting thermistor should work just fine. There are a lot of kinds, so choose properly. It should stay hot with the normal load, so be sure to provide good clearance around it.Hi Ed,
Thanks. I did a bit of investigation into what the 603 should need. I
don't have any way to measure the actual current draw at the moment, but
I've used the following:
* The smoothing caps (as replaced) across the four main windings are
charged by about 11.3 J
* The overall system fuse is 1.6A slow blow -- I am estimating the
operating current is probably not greater than 1A
* I've chosen a 120Ω 2A thermistor, e.g. Ametherm SL12 12102 -
I've never spec'd one of these before so let me know if anything is