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Author Topic: Neumann Power Supply Corrosion  (Read 2201 times)

terskelton

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Re: Neumann Power Supply Corrosion
« Reply #15 on: April 22, 2021, 06:46:23 pm »

Uwe,
I have a couple NKMu supplies with corrosion. I don't want to install a new regulator at this time but want to remove the Stabilyt cells and as much corrosion as I can so things don't get worse over time. You mention using vinegar on the corrosion followed by water or alcohol. Can I just immerse the entire chassis in vinegar and for how long? Maybe scrub a little with a toothbrush? And then water, etc. Maybe bake in an over at 120 degrees to dry out? I seem to remember using baking soda/water paste or is that for a different battery chemistry? Thanks. 
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uwe ret

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Re: Neumann Power Supply Corrosion
« Reply #16 on: April 25, 2021, 02:56:23 pm »

Do NOT immerse the entire supply in water, vinegar or any other liquid!

After removing (permanently) the Stabilyt cells, the alkaline residue needs to be scraped off and neutralized with a mild acid (like vinegar). You may have to perform the vinegar wash repeatedly, for which I suggest a stiff bristle acid brush or similar. Make certain none of the cleaning solution gets into the mains transformer, choke or rectifiers!

When everything looks clean, rinse only the affected area with clean water, but never use running water, which, again, may damage ancient insulation in the transformer and/or choke or ruin old selenium rectifiers.

You may replace Stabilyt cells with NiCd batteries, but their life expectancy as voltage stabilizers is severely limited. The suggested solution is replacement with a solid state (LM 317 or equivalent) circuit as recommended in previous threads on this and other forums.
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terskelton

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Re: Neumann Power Supply Corrosion
« Reply #17 on: May 05, 2021, 03:22:37 pm »

Uwe,
Thanks for the response. There are a lot of stories in the broadcast world of just hosing down equipment out in the yard, especially when it has been flooded for example.

The other day I had a new car battery installed and the tech sprayed something from a spray can on the battery connections, he said if there was any corrosion left the color of the spray would have changed and I had the impression the spray also cleaned.

I don't know if that applies to NiCd corrosion. I'm going to investigate this further. Thanks.
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Kai

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Re: Neumann Power Supply Corrosion
« Reply #18 on: May 13, 2021, 02:37:49 am »

The other day I had a new car battery installed and the tech sprayed something from a spray can on the battery connections, he said if there was any corrosion left the color of the spray would have changed and I had the impression the spray also cleaned.

I don't know if that applies to NiCd corrosion.
No need to spray (never spray!) strange chemicals, probably not intended for this use which possibly make things worse.

To clean certain areas of printed circuit boards I use a thin hose, taped to a (water capable) vacuum cleaner.
While applying cleaning fluid with a small brush - usually demineralized water + isopropyl alcohol - I vacuum away the fluid from the board.

This way I can limit the cleaning fluid to the contaminated areas of the board, preventing it from spreading the contamination.
At the same time this technique removes ALL contamination, as the cleaning fluid isn‘t just drying on the board, but completely sucked away.
Always suck away the fluid from the brush before dipping it into the fluid for the next dose, to keep the fluid clean.

This works well even with very high impedance circuits, where every little bit of residue disturbs the function.

Warning: Don’t do this with microphone capsule’s diaphragms.
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