Lab supply acting up

Am 13.04.2012 11:14, schrieb Don Y:

I knew similary effects with powersupps that has a thyristor (SCR) / triac preregulator, if the SCR was misfired (wrong time/phase) the transformer makes -ugly- noises...

at that age of the ps i would look for bad elytics first.

Jorgen

Does it have a fan in it?

Not much else to make a rattling noise, unless some capacitor or such took a *slow* dump, as opposed to the normal exit announcement.

I suppose it could have a hard relay in it,which could make such a noise, if "excited" in a particular way.

I have a ye good olde analog bench supply that relay-selects an appropriate tap on the transformer, based on the voltage desired. (to limit regulator dissipation).

With some voltage settings, the relay has problems deciding what tap to select -> rattling. A bit more hysteresis might help.

preregulator, if the SCR was misfired (wrong

About where are you located Don?

Over night during the lightning storm we had ~750 hits in the SF Bay Area.

I understand that power line currents induced by near hits can cause wild common mode and differential spikes at outlets.

:)

The sky is likely a better place to look. :)

--Winston

Maybe one or more electrolytic capacitors have dropped significantly in value, causing the relay to chatter- given the age that sort of thing is to be expected. Replace them and it should be good for another 30 or 40 years.

Possible. I've not looked inside the beast. I was repairing a small TV (using the lab supply in lieu of the "brick" for the set) and was intent on the *screen* as I applied power so was caught off guard by the horrendous rattle!

Also possible/likely. At low load (~20W) nothing seemed out of the ordinary. Only when the higher load was applied (70W) did things start to rattle (though no visible impact on the operation of the TV in question!).

I'll try to drag out a scope and have a better look at it over the weekend. *If* I can clear the rest of the kit off my bench before then!

So. AZ

I don't imagine we'll see any rain/lightning for several more months :> (though the wackierologists claim rain this coming weekend... but, I think they nibble on magic mushrooms pretty regularly!)

Something is unhappy. It *could* also be the *load*. I'll drag out one of the bigger lab supplies and see if *it* freaks out with the load as well. And, have a peek at the quality of the power being delivered to the set.

As with everything, it's just a matter of making time to

*do* these things... (sigh)

You more than likely have several caps in parallel, one of them most likely has kick the bucket!

Jamie

Rattling transformer laminations is a good place to start..

A storm produced >11,000 strikes in 30 minutes in Central Florida a few years ago.

--
You can't have a sense of humor, if you have no sense.

Florida has the record for strike occurrence incidence average over time, the world over.

Grrr... of course, it decided to rain TODAY! :-/

(Well, at least it will be a bit easier digging out the pomegranate!)

And...ALL non-union!

Good Luck!

Those suckers are tenacious!

--Winston

That's discouraging. I was hoping it would be a piece of cake (compared to the other *trees* I've felled) :<

The other trees I've felled tend to be in the 40' range. I.e., block traffic when you drop it across the roadway. :>

(make sure you do all your sitings/calculations correct lest it end up *on* something :< )

I dig up the stumps and root systems. Usually, because I want to put some other tree in the same place -- or very close by. E.g., the lime tree I took out weeks ago required clearing an 8ft dia "hole" to a depth of ~3 ft -- to make room for the

*new* lime that went in it's place. The larger trees have required removing several *tons* of soil to get the root systems out (one required 7 tons of *additional* fill to augment what was "lost" by the removal of the old stump -- no idea where it all went :< )

Ah, OK. So, if I dig it out like the other trees (I want to add a Blood Orange in its place) I shouldn't have any problems?

Understood.

I'll just opt for the "really big hole" approach. This has added benefit as it breaks up the soil in the area around the new planting and lets me augment the soil in a larger area than would happen otherwise. Seems like the trees produce better when allowed to develop better root systems.

It'll also let me run new "shrubblers" to replace the drip that had fed the pomegranate.

Yes indeedy.

I've been lucky. The trees I've knocked over had good clearance for 100 degrees, so I was confident I could drop them safely. Knock 'em over and cut 'em up.

Good on yeh! Let me know when you have nothing to do. I've got some neighbors with several grade-level stumps that they would be better off without.

Is this shovel-by-shovel or do you have a backhoe?

You shouldn't. Be aware that 100 little trunks can be more difficult to work with than 1 bigger trunk. The little trunks don't give you much to 'grab' onto. They bend out of the way rather than allow you to secure a sling, so the sling tends to slip *a lot*.

As you say, if you completely undermine the plant, you'll be able to lift it out en masse. That is a lot of shoveling though. 'Sounds like you would not be daunted by that!

Excellent approach IMHO.

--Winston

In Arizona I just cut them off as close to grade as I can, then dig around to expose maybe six inches deep. Fill with charcoal, and light 'er up. About a week later, fill in the hole ;-) ...Jim Thompson

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| James E.Thompson, CTO                            |    mens     |
| Analog Innovations, Inc.                         |     et      |