Topics

Washing a 7K scope

Ed Breya
 

I've got this 7403N that I picked up for cheap last year at a flea market. It was supposedly working, and came with three run of the mill plugs, for ten bucks. It definitely was not in working condition, having all sorts of PS problems, but I can't complain - waddya want fer ten bucks, eh?

Anyway, the insides are extremely filthy, so bad it's hard to see the parts under the grime. It looks complete, so I figured this might make a good test case for a washing. Then I'll at least be able to see what I'm working on and try to get it going again. It's an "N" model so has no readout, but it would be handy to run plugs like a 7D20 or 7D01 that make their own.

If It's too far gone, an alternative is to rebuild a 7603 into the husk. I have pretty much a whole set of guts that came out of a junked rackmount version, which combined with some of these parts, should approximately equal a fresh scope. Either way, this carcass is just too filthy to work on, even for me.

I ran across this old scope washing article today,

http://w140.com/tekwiki/images/1/18/Tek-wet-washing.pdf

which reminded me of this project, so here we go. I'd like to give it a shot tomorrow if it's reasonably warm out. The plan is to do detergent spray and cold water spraying outdoors, then drip-dry and compressed air for a while, then drying indoors with cardboard boxes and heaters. I don't have an oven big enough for such a piece. Only the mainframe will be washed, with as much stuff opened up as reasonably possible.

Has anyone done a 7K wash? I remember many discussions here about washing tube scopes and boards and such, but not 7K. Are there any special things to worry about, or other advice on the process?

Ed

Chuck Harris
 

No high pressure washing!

What I would do is first blow the whole thing out
with 30 PSI compressed air. So much of the grime will
just float away...

Then I would use a hand held squeeze pump sprayer with
a dish detergent (Dawn) and water mixture in it, about
the same concentration you would use to wash the dishes.
Set the nozzle to a shower sort of spray. Douse areas
that are dirty, but lay off any enclosed switches or
transformers.

Then using a garden hose set for a mist, rinse while the
chassis is on an angle, so the water doesn't pool anywhere.

Prop it up on an angle, and blow it again with compressed
air, again, not towards closed switches...

A big cardboard box and an old milk shed heater makes a nice
convection oven. Set the heater to low, and its thermostat
for something reasonable, and keep an eye on the temperature.

-Chuck Harris

Ed Breya via groups.io wrote:

I've got this 7403N that I picked up for cheap last year at a flea market. It was supposedly working, and came with three run of the mill plugs, for ten bucks. It definitely was not in working condition, having all sorts of PS problems, but I can't complain - waddya want fer ten bucks, eh?

Anyway, the insides are extremely filthy, so bad it's hard to see the parts under the grime. It looks complete, so I figured this might make a good test case for a washing. Then I'll at least be able to see what I'm working on and try to get it going again. It's an "N" model so has no readout, but it would be handy to run plugs like a 7D20 or 7D01 that make their own.

If It's too far gone, an alternative is to rebuild a 7603 into the husk. I have pretty much a whole set of guts that came out of a junked rackmount version, which combined with some of these parts, should approximately equal a fresh scope. Either way, this carcass is just too filthy to work on, even for me.

I ran across this old scope washing article today,

http://w140.com/tekwiki/images/1/18/Tek-wet-washing.pdf

which reminded me of this project, so here we go. I'd like to give it a shot tomorrow if it's reasonably warm out. The plan is to do detergent spray and cold water spraying outdoors, then drip-dry and compressed air for a while, then drying indoors with cardboard boxes and heaters. I don't have an oven big enough for such a piece. Only the mainframe will be washed, with as much stuff opened up as reasonably possible.

Has anyone done a 7K wash? I remember many discussions here about washing tube scopes and boards and such, but not 7K. Are there any special things to worry about, or other advice on the process?

Ed



Jim Ford
 

And don't forget to unplug it from the mains first!  8>()Jim Ford Sent from my Verizon, Samsung Galaxy smartphone

-------- Original message --------From: Chuck Harris <cfharris@...> Date: 4/23/20 7:44 PM (GMT-08:00) To: TekScopes@groups.io Subject: Re: [TekScopes] Washing a 7K scope No high pressure washing!What I would do is first blow the whole thing outwith 30 PSI compressed air.  So much of the grime willjust float away...Then I would use a hand held squeeze pump sprayer witha dish detergent (Dawn) and water mixture in it, aboutthe same concentration you would use to wash the dishes.Set the nozzle to a shower sort of spray.  Douse areasthat are dirty, but lay off any enclosed switches ortransformers.Then using a garden hose set for a mist, rinse while thechassis is on an angle, so the water doesn't pool anywhere.Prop it up on an angle, and blow it again with compressedair, again, not towards closed switches...A big cardboard box and an old milk shed heater makes a niceconvection oven.  Set the heater to low, and its thermostatfor something reasonable, and keep an eye on the temperature.-Chuck HarrisEd Breya via groups.io wrote:> I've got this 7403N that I picked up for cheap last year at a flea market. It was supposedly working, and came with three run of the mill plugs, for ten bucks. It definitely was not in working condition, having all sorts of PS problems, but I can't complain - waddya want fer ten bucks, eh?> > Anyway, the insides are extremely filthy, so bad it's hard to see the parts under the grime. It looks complete, so I figured this might make a good test case for a washing. Then I'll at least be able to see what I'm working on and try to get it going again. It's an "N" model so has no readout, but it would be handy to run plugs like a 7D20 or 7D01 that make their own.> > If It's too far gone, an alternative is to rebuild a 7603 into the husk. I have pretty much a whole set of guts that came out of a junked rackmount version, which combined with some of these parts, should approximately equal a fresh scope. Either way, this carcass is just too filthy to work on, even for me.> > I ran across this old scope washing article today, > > http://w140.com/tekwiki/images/1/18/Tek-wet-washing.pdf> > which reminded me of this project, so here we go. I'd like to give it a shot tomorrow if it's reasonably warm out. The plan is to do detergent spray and cold water spraying outdoors, then drip-dry and compressed air for a while, then drying indoors with cardboard boxes and heaters. I don't have an oven big enough for such a piece. Only the mainframe will be washed, with as much stuff opened up as reasonably possible.> > Has anyone done a 7K wash? I remember many discussions here about washing tube scopes and boards and such, but not 7K. Are there any special things to worry about, or other advice on the process?> > Ed> > > >

Bill
 

Never washed an oscilloscope but have have washed many PCBs used in our Bailey Net 90 Distributed Controls System in the Power Generation plants.  We shut down the cabinets and pulled the PCBs one at a time then washed them in Deionized water.  Dawn dish washing soap was the detergent we used with a soft brush to remove the grim.  After washing they were rinsed in more DI water then sprayed with aerosol Isopropyl alcohol.  The last thing done was blowing them off with aerosol air.   Did this many times over the years in the plants.  The PCBs were located in areas with lots of coal dust, chemical vapors, and flyash.  They were filthy but the cleaning process worked very well.  They were cleaned every 6 months.
Bill On Thursday, April 23, 2020, 9:44:36 PM CDT, Chuck Harris <cfharris@...> wrote:

No high pressure washing!

What I would do is first blow the whole thing out
with 30 PSI compressed air.  So much of the grime will
just float away...

Then I would use a hand held squeeze pump sprayer with
a dish detergent (Dawn) and water mixture in it, about
the same concentration you would use to wash the dishes.
Set the nozzle to a shower sort of spray.  Douse areas
that are dirty, but lay off any enclosed switches or
transformers.

Then using a garden hose set for a mist, rinse while the
chassis is on an angle, so the water doesn't pool anywhere.

Prop it up on an angle, and blow it again with compressed
air, again, not towards closed switches...

A big cardboard box and an old milk shed heater makes a nice
convection oven.  Set the heater to low, and its thermostat
for something reasonable, and keep an eye on the temperature.

-Chuck Harris

Ed Breya via groups.io wrote:

I've got this 7403N that I picked up for cheap last year at a flea market. It was supposedly working, and came with three run of the mill plugs, for ten bucks. It definitely was not in working condition, having all sorts of PS problems, but I can't complain - waddya want fer ten bucks, eh?

Anyway, the insides are extremely filthy, so bad it's hard to see the parts under the grime. It looks complete, so I figured this might make a good test case for a washing. Then I'll at least be able to see what I'm working on and try to get it going again. It's an "N" model so has no readout, but it would be handy to run plugs like a 7D20 or 7D01 that make their own.

If It's too far gone, an alternative is to rebuild a 7603 into the husk. I have pretty much a whole set of guts that came out of a junked rackmount version, which combined with some of these parts, should approximately equal a fresh scope. Either way, this carcass is just too filthy to work on, even for me.

I ran across this old scope washing article today,

http://w140.com/tekwiki/images/1/18/Tek-wet-washing.pdf

which reminded me of this project, so here we go. I'd like to give it a shot tomorrow if it's reasonably warm out. The plan is to do detergent spray and cold water spraying outdoors, then drip-dry and compressed air for a while, then drying indoors with cardboard boxes and heaters. I don't have an oven big enough for such a piece. Only the mainframe will be washed, with as much stuff opened up as reasonably possible.

Has anyone done a 7K wash? I remember many discussions here about washing tube scopes and boards and such, but not 7K. Are there any special things to worry about, or other advice on the process?

Ed



josephlevy
 

Hi
Look at 'TekScope' magazine for July 1972
The 'research' done was partly in the US navy maintenance depo at Keyport Wa. (and I happened to be part of then....)

De Joe 4X1RV

jim Madden
 

I would buy a pump sprayer from lowes or h depot thar you can pressurize with a few pumps and use desalinated warm water and dawn.jim

Ed Breya
 

The washing part is done, and it shined up nicely. I pulled a lot of stuff without unhooking, including the power transformer ass'y, the regulator board, high voltage box, and CRT socket. This made it a little awkward to handle, but much easier to flush everything out thoroughly. I pulled the bezel ass'y and found what could have been part of the problem - the camera power feed wires to the bezel had been gouged and frayed (not by me), and may have been shorting to the chassis. I also found a TO-92 transistor on the regulator that looks suspicious, with a crumpled up lead that may not be engaged in the socket. It's interesting the stuff you notice when something's opened up in the glorious sunshine.

Also interesting is that the HV box looked brand new on the inside, with not a speck of the usual electrostatically attracted and bonded grime. I think this unit may not have much actual run time on it, but you'd never know from the outer layer of guts. I think it was probably stored in poor conditions, and with the covers removed. The horizontal surfaces were all filthy, but the vertical ones not so much. Overall, it wasn't as bad as I thought.

After some compressed air and sun drying, it's now in an aerodynamically designed pile of cardboard boxes, fired by a small room heater/fan thing to dry overnight.

BTW before doing the wash, I tried out a little soda blasting. A slight layer of dust over the grime cleaned up somewhat with compressed air, but way more was needed. I have this mini-sand blaster type thing, which is a little jug on a venturi air gun thing. I put in some baking soda and fired away. It did clean off a bit deeper, but not enough to make me happy, and it would have been very tedious since my little compressor just isn't enough to keep up with this kind of use. A wet wash is still the best.

Ed