glued capacitors

sssboa

Super Member
Hi

Is there any electrical reason for these capacitors, ceramic and electrolytic being glued together and to a metal plate or capacitor glued to an IC or is it just to keep them from being loose? The glue is like tar or rubber or hot glue. The gear is 1977 Hitachi boombox.

tar1.jpg tar2.jpg
 
The first pic (tacked to IC) looks like possibly a polystyrene cap,probably a critical area for stability/value.These are very sensitive to soldering heat,so the leads are often left long on purpose.The second looks like a circuit board layout ''oopsie'' that required some long leads to overcome.
 
Typically, parts are glued because they broke loose during product qualification testing, which includes significant vibration and physical shock tests. This ensures that parts will not break loose during conditions to be normally expected during shipping and use.

Enjoy,
Rich P
 
Yeah, maybe, but to a heatsink?

That also maybe suggests the electrolytic is heating up because of ESR?
 
Gluing an electrolytic onto any surface which heats up only faster evaporates the electrolyte and reduces lifespan, since lifespan is proportional to temperature.

Oh, right. Consumer equipment. Yeah, that.
 
Thats NOT a metal plate shown in the 2nd. picture.

It is a ceramic plate with circuits on it.

You can tell it has wire leads going to the PCB and has a pin (just under the caps) marked #1.

Please don't try and pry them off the "plate" with too much force or CRACK goes the ceramic!

Mark T. :music:
 
Thats NOT a metal plate shown in the 2nd. picture.

It is a plate with circuits on it.

You can tell it has wire leads going to the PCB and has a pin (just under the caps) marked #1.

Please don't try and pry them off the "plate" with too much force or CRACK goes the ceramic!

Mark T. :music:
It's a plate on 14 pins (vertical in the picture), which is part of the circuit. The bundle of caps glued to it are C412R, C412L, C444R, C444L. The plate seems painted metal but it's marked IC402, is it an IC? There are 3 such plates on the board, marked as IC401, 402, 403. IC's that look like chips are marked IC301, 302 and so on.


Clipboard01.jpg
 
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Ahhh, that is a SIP, an acronym for "Single In-Line Package".

Back in the day some integrated circuits were packaged in a long vertical package. It was common to have memory packaged this way in the late 1980s because of improved density.

It has been so long since I've seen one I'd forgotten about those!

Usually made out of plastic, just like ICs. But sometimes these were ceramic with surface mount devices, must like a ceramic circuit board with metal traces.
 
It was the first boombox I ever tried to restore. Very difficult to unsolder anything. They used entirely different technique to solder it together than in separates, solder tin is on entire traces, not just under components, but quality of PCB is superior. I managed to remove and test some caps, very small aluminium electrolytics like 0.1uF Nippon caps and still measured better than new ones would I guess (2ohm under 9v) if they still used them of this size. I singled out the only Sanyo cap on board, 0.22uF which measured very high ESR (24ohm), the rest mostly Panasonic and some Nippons - excellent.
 
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