Re: What replacement for 22uF tantalum beads?


Tom Gardner
 

On 19/03/16 18:07, analogaddict013@... [TekScopes] wrote:

I wouldn't have heard a clicking in any circumstances short of someone >dropping
a CRT :(
Wait.... are you saying you dropped a CRT?? I don't remember hearing about that!
No, not quite :)

There's a dent in the case that makes me presume it was dropped, but the only symptom was lack of brilliance control - the CRT could be used as a torch. After fruitlessly replacing the HV diodes (but not the HV caps), I pulled the CRT and found the grid was internally disconnected.
(All other caps work fine too, so far, touch wood, fingers crossed)

Now I /was/ thinking of lobbing the CRT into a dustbin to shatter it and then extract the pretty metalwork. Instead a friend told me that portable glass-cutting bandsaws existed, so on Thursday we sawed the neck off. Now all I have to do is decide how to mount the CRT.

Serendipity: I now understand the source of the pretty pattern thrown on the screen by a defocussed beam: the mesh.

It would take 60s to start, unless it had previously been "warmed up". That >was
C1848 (almost certainly) in the inverter being a deceptive little b*gg*r. Hence
I had already recapped all the ali electrolytics in that area, and this was an
unpleasant surprise.
That's certainly interesting.. One of the 485's that I've been attempting to get running will start up normally at first.. run for 10 seconds, then the U1610 kicks the inverter off. The 20ms sampling period is getting stretched to over 50ms somehow, and it's not the 2.7uf 50v tantalum cap. It's got me a bit confused, but maybe I should go back and lift/measure that cap.
My presumption is that after power had been applied for 60s, the electrolytic had "reformed" sufficiently that it worked adequately. The reforming lasted for 6 hours, so that made it possible to have two or three "what happens during power on" experiments per day. Understanding the circuit and careful planning helped.

Join TekScopes@groups.io to automatically receive all group messages.