Weather related scope faults?

[Diabolical Artificer]

Today in the workshop I turned my Tektronix 585A on to monitor an oscillator on the bench, no sweep, odd. I then tried my Tek 545B, turned it on, no sweep, odder & odder, both were working fine yesterday.

As you all know we've had a prolonged cold spell recently, today the weather is a lot warmer. I noticed all my cables felt "greasy" to the touch, high humidity?

The only explanation for both Tek 500 series scopes going gaga is high humidity and the possibility that some valves in the scopes have died: my workshop is essentially a lean to on the house, no heating, I've noticed valves in scopes stored in sheds have gone to air, possibly caused by thermal expansion & contraction due to the cold.

Has anyone had similar test gear issues recently?

Andy.

[Refugee]

My test gear is all indoors.
I did notice today that all metal items in sheds and unheated buildings were covered in condensation.
I would guess that there is condensation on some internal components in the equipment that is playing up.
Just move the equipment into a warm dry place for a few hours. Electric heating is best if you want to actively dry it out.

[Mark Hennessy]

Yes, this sudden change in the weather has brought a lot of moisture in the air. Anything below the dew point will definitely have condensation, and given the thermal mass of something like a 'scope, it'll stay cold for a lot longer than other things. Hopefully that's all it is - a bit of leakage. Probably best to not operate it until it has warmed up - though there's no doubt the heat generated by the 'scope itself will accelerate the process, there is a risk of consequential damage if internal circuit conditions aren't right.

I've no experience of valves in cold conditions, but given the range of temperatures they normally see (room temp to operational temp), it's hard to imagine that being 10 or 15 degrees cooler will bother them. We experience temperature in a very non-linear way, but glass and metal probably don't

The gear I use most is in the cellar. Some of it is in the room above. But the stuff I haven't used for aeons is up in the attic. Not many valves, admittedly. It does seem to hold up well - I've yet to notice corrosion as a result of humidity. Hope the radio collection is OK! It is well ventilated, but that works both ways...

[ppppenguin]

This is top quality professional kit that I would expect to work come hell or high water. But there must be some level of damp that will stop it working properly. Of particular concern are the EHT transformers which are a known weak spot on Tek 500 series scopes.

[BusyBee]

I have noticed, in one of my multimeter handbooks, that there is a variation of model designed for high humidity environments. It is a danger though that a sudden change in cold to hot would bring bad condensation.

There has been talk, in the past, of valves going to air in certain circumstances. Obviously the glass and metal contract a lot in sub zero conditions so any possible gap, talking microscopic level, may open up?

Tracy

[Diabolical Artificer]

I haven't had a look at the scopes yet, it's odd both suffered from no sweep though there is some glow on the CRT. Other test gear is working ok including a scope and HP8903B. I think I'll drag them out of the workshop and pop them near the fire for a few days.

Andy.