ppppenguin

A great description of how Tek used to wash their scopes.

http://groups.yahoo.com/group/TekSco...20Phillips.pdf

cmjones01

That's brilliant. I've always wondered about the effect of wet washing on things like inductors. I 'washed up' a BBC Micro circuit board with no ill effects, but have never been brave enough to try it on anything analogue.

If it's good enough for Tektronix, it's good enough for me. Out with the hosepipe.

beamcurrent

I've washed a fair bit of stuff over the years, I once had a TV camera chassis in the bath! Rinse well with clean or distilled water.

I find a compressed air jet very good for drying equipment, it blows the water out of all the crevices.


Brian

Herald1360

Still waiting for admission to Tek group so I can look

I've inadvertently washed a few things, mostly digital watches- they usually seemed to recover OK after a swill in meths and a gentle bake in the oven!

murphyv310

Hi.
I have posted here a couple of items I have washed before mamely a Murphy V200 & an Ambassador TV4 chassis, it raised a few eyebrows!! Not a thing wrong with wet washing so long as the "board, chassis etc" is propery rinsed and dried, I've been doing it for years.
Trevor

__________________
Cheers,
Trevor.
MM0KJJ. RSGB, GQRP, WACRAL, K&LARC. Member

cmjones01

That settles it, the BRT400 is definitely getting a bath!

I've cleaned a lot of plastic case parts, computer keycaps and things by putting them in the dishwasher (with detergent, the whole works) but I think that may be a little harsh even for tropicalised electronics.

ppppenguin

When washing lesser equipment please bear remember that Tek designed their stuff to very high standards and also had replacement parts available in case something got damaged by water. Neither of these apply to domestic electronics where some components may be too vulnerable for comfort. Especially wound components which are hard to replace.

One thing I routinely wash is computer keyboards. A good scrub with detergent and water, rinse in the shower and dry in the airing cupboard. The only precaution I take is to keep the keyboard upside down all the time to minimise water running deep inside. Never had a failure yet and nice clean keyboards are a pleasure to use.

cmjones01

I'm most worried about things like varnished inductors in case there are unseen (or seen) cracks in the varnish.

I once tried gettings assembled PCBs coated with varnish to keep moisture out. It turned out to make moisture-related problems worse by increasing the number of crevices which could trap water, and I think the varnish gradually absorbed the water too. Whenever one of the offending items came back for repair (which was more often than they should have done) cleaning the varnish off was the first job. The problems haven't recurred.

This whole thread might explain why my venerable Tek 535A is clean as the proverbial whistle inside despite its advanced years. I'd always wondered about that...

Nickthedentist

Reminded me of this: https://www.vintage-radio.net/forum/...8&postcount=17

Can we view the link without being members?

Nick.

AlanBeckett

Acrylic or Urethane conformal coating compounds don't suffer from these problems if applied properly. Dipping is best. On the other hand, if you want to repair a PCB getting them off is another matter.
Alan

Oldtestgear

One important consideration is whether the equipment is using modern SMD components. All plastic parts will slowly absorb moisture but new SMD parts may not be sealed at the edges -- the actual silicon is showing. On these parts water ingress is a real risk & likely to cause terminal damage. This is one of the drawbacks of wafer scale packaging. As the wafer is sawn or scribed the edges are exposed. Can also have interesting side effects as most semiconductors are light sensitive. The law of uninteneded consequences.............

Another reason why SMD components are stored in low humidity & may be conditioned in an oven before use. Exploding parts during soldering is not reccomended!


Phil

Mike Phelan

I've washed several TV chassis with PCB's (mainly Philips G6 / K70) by using warm water and drying in the airing cupboard - without any problems at all.

__________________
Mike.

coil1234

I Haven't looked at this yet, but I definately remember being told in the late 70's, either by a more senior engineer or by a Tek Rep that this was how scopes in for service were cleaned at Tektronix. Basically dunked in a big bath, was there something in a Tek news letter about this?
These were scopes of the 5xx series. Many coming into Marconi Comms Cal dept were full of dust inside and took a lot of cleaning up, usually by compresed air.
Incidently, I had a relatively modern and grimey PCB in for repair at work today, I had no worries about scrubbing with washing up liquid under the hot tap then thoroughly blowing with compressed air and then cooked in an oven, most modern assemblys use a water soluble flux and are cleaned in a similar fashion.

Mike A

Oldtestgear

I think I ought to clarify my earlier comments. The micro SMD packages now being used are actually packaged at wafer level & cut/scribed after electrical test -- hence the exposed edge of the die.
These are used in the same way as conventionsl SMD or BGA parts. This can include water based cleaning processes. The distinction between an industrial process and home will be the the water quality. Check around & most water based cleaing processes require ULTRA PURE DEIONISED water for the final step as a minimum.
Old style components are much less susceptible to contamination than the latest parts partly due to the wafer processing and the thicker packaging. There are exceptions though -- how many remember the term "purple plague" ? Contamination in the package attacked the bond wires which eventaully dropped off. A catastrophic failure mechanism caused by poor processing.
Tap water contains a whole host of chemicals that are deadly to modern components and adding washing up liquid (usually containiing salt) will only make the problem worse.
A useful article can be found here:
http://www.assemblymag.com/Articles/...00f932a8c0____

National Semiconductor also has some useful application notes on the Micro SMD package. The question of light sensitivity only relates to analogue parts according to the Seminar given by NSC a few years ago.

Unfortunately modern microelectronics is even more of a challenge to the home user/repiairer/engineer than ever before.

What Tek did in the 1970s was based on the technology in use. Times change and so does technology. There is unlikely to be a problem washing an old board, just don't risk it with a new one unless you are prepared to buy a replacment.
Just my opinion based on 20+ years in the semiconductor industry.

Phil

Phil

dazzlevision

Hello,

Around 1967, "Practical Television" had an article (with pictures) about Tektronix washing their scopes (returned to Tek for service)!

Regards,

Dazzlevision

Billy T

Companies restoring computers and other electronics for insurance companies after fire & flood damage etc simply wash them in de-ionised water then dry them in a low pressure heated chamber. Other products are used to remove soot residues etc. but in the end it all comes down to the water and enhanced evaporative drying.

It is a very successful process and taking heart from their experience I have washed some electronics boards myself with no problems, but drying thoroughly and as quickly as possible seems to be an essential factor in that success.

Cheers

Billy

Dean Huster

Not a bath. I worked for Tektronix in their Dallas and Oklahoma City Service Centers. We had a washing booth where LOW PRESSURE air was mixed with a water/Kelite detergent solution. After removing all the outer and inner covers, the scope was thoroughly washed and even more thoroughly rinsed. LOW PRESSURE air was then used to force the greater amount of remaining water out of all the nooks and crannies. Finally, isopropyl alcohol was squirted in the attenuators of the "newer" scopes ("new" 400-series, 5000-series and 7000-series to displace water) and then the scope and its removed parts were put into a large low-temperature oven for about three days to dry up all the water. After removal from the oven, the 500-series had their fan motors lubricated and then the scope was sent to the technician to repair. (The washing was done by a lower-paid worker who wasn't an electronics technician.)

The washing was done for scopes that had internal fans. We didn't wash the 422 since it had no vent holes and never got dirty on the inside. Any instrument like that back then (e.g., the 200-series, 1500-series) were not washed because they never got dirt inside them. New scopes without fans are not washed. Even though I've not been at Tek since 1982, I would assume that washing is all but forgotten with the modern instruments, not because they can't handle the process but simply because they don't need it.

We NEVER, ever washed a Telequipment scope. They couldn't handle it.

Washing sometimes actually fixed some problems, rarely caused new problems and certainly helped reliabilty by removing a lot of insulating dirt that had accumulated over years of use.

Dean