opened up an old amp with glass caps(?)

[impsick]

i raped an old sansui( spelling ?) today and found a bunch of Elna caps which is cool cuz i needed the ratings it had inside.

but i came across some glass caps. low ratings mostly. small in size. whats the deal with these? any body familiar with glass caps?

 

[pinkmouse]

Pics?

 

[impsick]

ok ill put some pics up once i get home. im not 100% sure they're caps but on the pcb they are in the spots labled w/ a C####

 

[bobgroger]

Might be Polystyrene. Clear plastic body with silver foil inside. Stable, decent tolerances, prone to short IIRC.

Bob G.

 

[impsick]

yes bob those are them.
sorry havent made it home yet to put pics up but ill do that anyways cuz there were some big elna caps in there too.

 

[I_Forgot]

Those caps are quite reliable, and very high performance. The reason you don't see more of them is that for a while no one was making them. I think there is at least one company that does now, but the others that stopped, stopped because there was no way to make them in chip form. The problem is that the dielectric melts at very low temperatures, so soldering them is tricky. With a leaded part you can clamp a heat sink on the lead being soldered to keep the heat from going up into the part and melting the dilectric. With chip caps there is no way to do it.

Keep those caps, and be careful with them when you solder them.

I_F

 

[impsick]

i forgot,

thanks alot for that info. very useful. i would have melted them all. haha. good looking out.

 

[impsick]

ok got some pics now...

An externally hosted image should be here but it was not working when we last tested it.

these transistors are glass. whats the deal with these guys?

An externally hosted image should be here but it was not working when we last tested it.

also inside was some other caps...

An externally hosted image should be here but it was not working when we last tested it.

An externally hosted image should be here but it was not working when we last tested it.

oh and check out these guys with the heat sinks on them. one has a diode on top of it

An externally hosted image should be here but it was not working when we last tested it.

 

[djQUAN]

I have come across "real" glass caps.

they look like the diode in the second pic but you can see an SMD chip capacitor inside it.

 

[impsick]

the first pic is a real glass cap. the reflection just made it look as though its not see through. and in the 2nd pic if you look to the left, thats a glass cap. a "real" one

 

[I_Forgot]

Those transistors aren't glass. It is just shiny black epoxy.

The heatsink and "diode" are a common arrangement. The diode is either a diode or more likely a thermistor used to provide thermal feedback to maintain bias at a more or less constant level even as the transistor heats up.

I_F

 

[impsick]

word.
i wanna say the transistors are barely transparent though. iim probably trippin.
cool

 

[I_Forgot]

It's possible, but unlikely. Transistors are light sensitive so they are normally packaged with opaque materials to prevent light from striking the die. I think some very early transistors has transparent packaging until they realized the problems it was causing.

I_F

 

[impsick]

good info. cool.

 

[cliffforrest]

It's possible, but unlikely. Transistors are light sensitive so they are normally packaged with opaque materials to prevent light from striking the die. I think some very early transistors has transparent packaging until they realized the problems it was causing.

I_F

Absolutely correct.

Early red-spot OC71 (Mullard) germaniums were actually in a clear epoxy potted case sprayed with black paint!

Scape off the paint and there was a very useful phototransistor (OP71?? - I can't remember)