leaning PCB's

[Keith Baran]

Hello all

I just picked up a Marantz 1060. It needs a re-cap but I'm working on another project now and will not have time for the next several months. I want to use the amp in my office, but it is filthy inside, piles of that thick dust. Blowing out with compressed air helped but I was wondering two things. Is it ok to take a spray bottle with 91% Isopropyl alcohol and spray down the boards? And if it is, is it cool to do it while they are still in the unit? Bottom is off, sides are off, setting upside down, spraying up at the boards so fluid will drip off. Then a day or two in the hot sun? Or am I a lune for even considering this?

Thanks for any advice

Regards

Keith

 

[roger2]

@Keith Baran Well, you may be a lune but not for considering this idea

I would suggest standing the amp on one end (side), position paper towels to catch run-off, spraying 91% IPA liberally, and gently applying a small, soft artist' brush where needed to clean tight spaces. I don't think the hot sun treatment is necessary but, who knows, it may help to dispel odors, I don't know. Just make sure all of the IPA and water (the other 9%) has a chance to thoroughly evaporate before powering the unit on.


EDIT: For clarity...the unit should be unplugged for several hours, preferably overnight, before spraying. In some amps, capacitors can hold a charge for some time after power down. Also, there is a product similar to IPA called "rubbing alcohol" that could contain unwanted additives and should not be used for this cleaning procedure. Make sure the only ingredients are isopropyl alcohol and water.

 

[Keith Baran]

Thank you sir

 

[Alan0354]

alcohol and then compressed air to dry.

 

[arts]

alcohol and then compressed air to dry.

Please go light on the compressed air pressure.Some guys think they're starting a turbine.... 10 to 20 psi should be adequate.
Use the IPA with a couple of drops of dish soap in a water mix. Setting the unit in the sun for a couple of hours is a good plan,as water can gather (hidden) beneath components on the board and needs to be ''baked out''.

 

[ChrisMarantz]

You might be surprised how well a soft brush and a vacuum will clean your Model 1060.

The idea of spraying everything to clean it is not as easy as you might think. - Chris

 

[Binkman]

right above. vac off dust bugs, light brush and q-tips it goes pretty fast, too.. make sure you don't bleed off any pcb marks.+/- etc;. I like the vac job because air blow just blows off junk around and around again. I like this method because I can see stuff as I clean it and cleaning solder joints reveals a lot of bad cold or aged solder, too.

 

[BinaryMike]

I wouldn't use alcohol because it dissolves solder flux, of which there is a great deal in most of these old chassis, and it could leave troublesome deposits inside pots and trimmers. I've cleaned hundreds of stereo components with warm water and mild detergent, however, and never had any negative results aside from losing the dial glass markings in an old tuner or two. Dial glass always got removed for separate treatment after that! There's a huge thread on this topic somewhere here.

 

[roger2]

@BinaryMike - I would tend to think that detergent, and/or warm water, which I assume to mean tap water (which is never pure and contains minerals), would be more likely to leave residue than IPA which is just alcohol and (I would assume) distilled water, both of which should evaporate completely, shouldn't they?

I never heard of any reason not to remove old flux? Could you elaborate on that please?

 

[BinaryMike]

I've got nothing against removing the flux, but you need a huge amount of alcohol or some other solvent to remove it completely, and if you don't remove it completely then residue in the wrong places can be devilish. Electronics manufacturers used to deal with this issue by continuously distilling the solvent. Nowadays, they use water-soluble flux or no-clean flux. Tap water certainly could be problematic in some parts of the world, but it's no problem where I live, at least for circuitry that's not dependent on extremely high insulation resistance. My methods were derived from an old Tektronix application note, and I used the detergent recommended by Tek; "Spray-White," if I recall correctly.

 

[roger2]

I am just thinking of stuff getting inside of open trimmer pots and such. I'll take my chances with 91% IPA before detergent and/or tap water. But as you say, you've used that combo many many times with no problems. Flux dissolved by alcohol is not something I had considered, and may be a valid concern. But the way I do it there are copious amounts of IPA washing over the boards. Lots of people do use IPA and I am not aware of anyone reporting a problem. Wouldn't purpose-made PCB cleaners dissolve flux too?

 

[Alan0354]

That is a concern if there is a lot of flux on the board. I just get too used to clean pcb of the later electronics, those old electronics never clean the flux and it's all over the place. Alcohol might not be the best idea after all.

 

[roger2]

That is a concern if there is a lot of flux on the board. I just get too used to clean pcb of the later electronics, those old electronics never clean the flux and it's all over the place. Alcohol might not be the best idea after all.

Flux is mostly on the solder side, where there are no components other than the occasional cap or resistor. The number of AK'ers who have used alcohol over the years to clean boards, with no reported issues I am aware of, is significant. IPA is a generally accepted method of cleaning PCBs, although, as with anything, there are other ways that some prefer.

There are purpose-made PCB cleaners, do these not dissolve flux? What about flux removers? Should these products not be used for fear of dissolved flux doing harm?

 

[Alan0354]

It's not about cleaning the flux, there are a lot of solvents that clean flux. It's when the flux dissolves, it runs all over the place. Then the solvent evaporates and leave a thin film of flux over the surface. you get into the volume pot or trimmer pot or anything mechanical, it cover to surface. It is different if you take out the board from all the mechanical parts and spray and clean, but inside the amp, you better be careful.

 

[Hyperion]

It's all a question of degree, you have to be careful and not go splashing the stuff (whatever you use) all over the place. Set boards at an angle ('leaning PCB's' ) and allow boards to drain off onto cloth or paper towels, position these so that the residue doesn't go where it can cause problems. Wrap sensitive stuff in cling film or other plastic and/or paper towels, use rubber bands, clothes pegs and whatever else to achieve this. Finally, if you find you can't clean something without flux residue or whatever getting where it shouldn't then don't clean it. Personally, I am not worried about trim pots (for example) getting flux residue on them, because I change them all anyway!

 

[roger2]

It's not about cleaning the flux, there are a lot of solvents that clean flux. It's when the flux dissolves, it runs all over the place. Then the solvent evaporates and leave a thin film of flux over the surface. you get into the volume pot or trimmer pot or anything mechanical, it cover to surface. It is different if you take out the board from all the mechanical parts and spray and clean, but inside the amp, you better be careful.

@Alan0354

I find it amusing, and somewhat troubling, that only 22 hours prior to the post quoted above you originally posted advice contrary to it

alcohol and then compressed air to dry.

 

[roger2]

IMO the fear of dissolved flux damaging parts is a bit of a red herring, and I am concerned this idea may instill doubt in the minds of some where there should be no doubt.

Flux residue is found on the solder side of PCBs. Often it is thick and covering adjacent tracks, pads, or posts, yet the amp works OK. If in this condition for 40 years in a vintage amp, I see no harm in thinning it down should an imperfect attempt be made at removing it. IPA is cheap and it does the job. Other products exist that are specifically made to do this job.

Pots, trim pots, etc., are on the other side of the board. When cleaning the component side, my preference is again IPA, because there is nothing in it that will leave residue when it evaporates.

No doubt it is conceivable that when cleaning the solder side of a board, someone could be so careless and/or sloppy that some of the cleaning solution carrying dissolved flux, regardless of what is being used, could somehow find its way into vulnerable parts on the other side of the board. Extremely unlikely, but hey, anything is possible. If someone is that careless they should not plugging in an amp, let alone working on one.