unpotting opamps

[pucho812]

Anyone have suggestions on how to unpot a doa. 

 

[JohnRoberts]

With a sledgehammer and chisel... watch out for your fingers.

Or just design yet another one..  ;D ;D ;D

JR

 

[pucho812]

this is for repair on a discrete opamp. no need to trash it when I can fix it... 

 

[thermionic]

You'll need such nasty stuff to dissolve the compound that, if it didn't need fixing before, it certainly will afterwards

 

[JohnRoberts]

If they potted it to prevent people from seeing what is inside, it will not be easy to take apart.

JR

 

[pucho812]

yeah that's what I was afraid of. Seems a waste to chuck  them out.

 

[CJ]

you could try a heat gun and ice pick,

slow going but it might still be fixable after the take-apart,

did this with a Valley People and a DBX VCA,

 

[gyraf]

+1 on heat gun and xacto-knife. Takes a good deal of ventilation, or unhealthy.

A friend of mine combines this with soaking-in-acetone for a week or more - but only for modules you have more than one specimen of, as some parts may get lost in the process.


heat:
http://kevtris.org/Projects/votraxpss/unpot.html

For silicone-based potting there is a suggestion of using "silicone sealant remover" from hardware store.
http://www.electro-tech-online.com/threads/removing-potting.34115/

Sodium hydroxide - Dichloromethane:
http://camerahacks.fr.yuku.com/topic/1021/Epoxy-blob-removal

Take care!

Jakob E.

 

[mjrippe]

If it is something easily available (2520, 990, etc.) it is probably not worth your time.  For something unobtainable it is a last resort.

 

[MicDaddy]

looking at IC Decapsulation, something similar should work.  http://www.t4f.org/articles/ultra-low-cost-ic-decapsulation/ 

If you just want a peek inside and have a local testing facility,  Non-Destructive X-ray Testing may allow that. 

 

[synthiaks]

Uh... This is my Horror. I have a half woking Yamaha SY-1 with the GX "Potted ICs" inside. They all have Electrolytes in there and i suspect that the VCA is broken. Or that the Transistor Bias is wrong. Thats why it just sits at my bench staring at me with sad eyes.  I don't even dare to start with it.

 

[12afael]

people repairing Junos are using acetone.

I 've unpotted a bass emg pick up with the most important component... patience.

 

[MicDaddy]

people repairing Junos are using acetone.

I 've unpotted a bass emg pick up with the most important component... patience.

The potting on those cermic boards for the Juno isn't quite the same stuff I've seen on 2520 footprint or other opamps.  Acetone is like blowing a kiss at that stuff.

Acetone does work well on the 80017A.

 

[mrphotodude]

start off with technical alcohol (100% or as close to it as you can get). Use a chopstick or non destructive tool(wood or plastic) and see if the epoxy, polyurethane ect starts to melt and become pliable. If not, use a heat gun with a tip to concentrate the heat in a small area and work off the gunk with a chopstick filed down to a chisel. If you use metal tools, you may chip a component. If it is a hard plastic, you can use a dremel with a microbit but be very careful. Here is part of the 2M (micro miniature)guide from navy/marine core for circuit repair.
http://www.navymars.org/national/training/nmo_courses/nmoc/module14/14186_ch3.pdf