Returning to valve equipment for greater reliability?

Where can I find a tube based four channel, 400 MHz Scope with IEEE_488 interface, that is calibrated via software? One that I can save the image, and print it out or save for future reference? How many tons of air conditioning will it need to keep from burning a hole through my floor?

ng an

nd

it

The OP story doesn't make much sense, unless he/she buys orphan equipment that is very vulnerable. I have used Tektronix and HP/ Agilent oscilloscopes and spectrum analyzers and other electronic equipment since the late 1950's in all sorts of climates and never had problems like the OP quoted.

an

I have a Tektronix 324 scope that I pried out of mud, after a bulldozer ran over it. I gave the owner of the scrap yard $20 for it, and hosed off the mud. I loose Berg terminal was repaired, and I made a power cord for it. That was about 25 years ago, and it still works. An old Tek scope like the 535 will need new caps, and calibrated no matter what the tube crowd thinks.

Maybe the scopes in that story were near the sea and were eat up with salt. I saw a pile of old HP 5245l Frequency counters stored in an non air conditioned building near Melbourne Florida. Just touching any of the transistors was enough to make the leads break off.

There are many more damp climates than NSW Aus. Florida is likely one of them. l-)

Damp? You can grab a handful of Central Florida air, and squeeze a glass of water out of it! I've had it take all day in the hot sun for a towel to dry on a clothes line. :(

e a

Been there, done that, in the 1950's. With climate change I don't think things are getting any better.

You can watch rust grow, on a slow day. ;-)

"Nutcase Kook"

1. The "correspondent" lives in very damp part of NSW - there are a tropical rainforest areas in the north of the state.
2. SS equipment dies due to high levels of moisture - which is correct.

Almost anything left around in a very damp environment will acquire a flim of water - so needing drying out before use.

Valve equipment left on 24/7 would avoid the problem - which makes the valve life rather short.

Air conditioning the equipment room is the obvious solution.

BTW:

Will NK ever wake up what a jerkoff he is ?

.... Phil

It seems an equivalent to trying to use equipment stored in sheds in the otherwise more equable climate of the UK. Corossion of switch contacts, mould growth from condensation and consequential extraneous partially conductive tracks. Older equipment had more resilient contacts materials and generally bigger dimensions, seems to make them more reliable in such situations

Valve equipment becomes thoroughly warmed and is usually designed to have a good air flow through the casing; this will dry it out and prevent tracking and corrosion if it is used regularly.

Because high voltages are involved, good valve equipment is designed with long tracking distances and good insulating materials (big tagboards and ceramic or P.T.F.E. standoffs). Transformers on good valve equipment are usually potted or oil-filled. Cheap valve equipment with open transformers, printed circuits and small track clearances is just as vulnerable to tracking and corrosion as modern transistor equipment.

Fully-sealed transistor equipment should, in theory, be just as reliable as good valve equipment; but if the sealing is the slightest bit imperfect, the wet will get in and stay in, causing worse conditions than if it wasn't sealed at all. This sort of kit will then be less liable to recover than the equivalent valve kit because it will never warm up enough to dry out. A small contact heater would be one possible answer; it could operate permanently, so as to keep the casing a few degrees above ambient and help to prevent further condensation.

It might be possible to reduce the filament voltage when in standby, thus increasing the life of the tubes. The "instant on" tube/valve TV's of the 1960's did that.

In a past life, I designed marine radios, some of which were used in high humidity tropical areas. I recall one warranty return where the insides of the radio were covered with a thick layer of mold growth. It was gross. The radio has to be designed to survive such an environment. That means vertically mounted PCB's to drain condensation, self-draining connectors, drain holes on the bottom of the radio, conformal coatings where possible, fungicides, good ventilation to remove moisture, galvanic compatibility between metals, gold connectors, and low impedance designs.

Sealed boxes didn't work as moist air always sneaks into the box. Pressurizing the box was the only system that really worked. Such hermetically sealed boxes were deemed maintenance problems as they had to be refilled with dry air after every repair or adjustment.

The really critical part was the low impedance design. At the time (1970's) it was common practice to use high impedances to reduce power consumption. That was fine if the board was dry, but a little moisture on the PCB would cause the circuit to go nuts. While low impedance designs were not a real solution, it reduced the problem to manageable levels. Running the radio immersed in salty water was the basic test. It didn't have to meet spec under water, but it shouldn't fail. Anything that moved (trimmers, pots, controls, switches, speakers, meters, etc) were the real problems.

I'm not so sure that heating the radio would have produced anything useful. It would have prevented condensation under some circumstances, but done nothing if the radio were turned off. Also, heat tends to promote mold growth. There was a crystal oven in one radio. I would expect the heat from the oven to prevent condensation. However, when the various radios came back covered with mold, it was the oven area that seemed to have the greatest accumulation of mold.

Yep. A/C drops the humidity level. The trick is to not create any situation that condenses moisture. That's not easy.

There is a certain fascination with tube/valve equipment. However, I would not want to carry a tube type cell phone, calculator, or laptop. Once we embark down the road toward miniaturization and increased component density, it's difficult to turn back. Might was well make the best of the unreliable junk we have today as the tube/valve alternative is unlikely to fit or function.

flim

The problem is in Nimbin , NSW, Australia, with loads of river water around

"Nutcase Kook" "Phil Allison"

The place is chock full of dope smokin' hippies !!!

And it is semi tropical too.

Trust NK to have a contact there.

... Phil

im

I worked inside Cheyenne Mountain, Colorado in the mid-1960's on the military installation there. It was in the early stages of construction, the building inside the hollowed-out mountain was constructed, but the mountain itself was still dripping moisture onto the building and the air exchange system was not operational yet.

Humidity was 98% or so, at about 60F. There was mold growing on all the electronics in the telco products that I was trying to debug. The gold-plated pwb circuit pack connectors even had mold growing on the contact fingers. Needless to say, the connections were not reliable. Fortunately for the USA Defense System, they did get the humidity down and the communications equipment went on to become reliable.

flim

I worked inside Cheyenne Mountain, Colorado in the mid-1960's on the military installation there. It was in the early stages of construction, the building inside the hollowed-out mountain was constructed, but the mountain itself was still dripping moisture onto the building and the air exchange system was not operational yet.

Humidity was 98% or so, at about 60F. There was mold growing on all the electronics in the telco products that I was trying to debug. The gold-plated pwb circuit pack connectors even had mold growing on the contact fingers. Needless to say, the connections were not reliable. Fortunately for the USA Defense System, they did get the humidity down and the communications equipment went on to become reliable.

If you include interpretting flocks of geese as incoming Russian missiles , and going to DEFCON whatever , as reliable.

I only said the communications equipment (AT+T four-wire switches) became reliable. All the other "stuff" was not in my baliwick.