bug dissected

[pontiacpete]

Here's a picture of a optocoupler, optoisolator, photocell or bug or whatever they go by, dissected, for anyone whose interested in seeing or who hasn't yet bother to do this themself.
I wonder why this one went bad..??

[Old Tele man]

...originally was: (a) neon bulb mounted face-to-face with (b) light-dependant resistor (LDR).

...some newer replacements use LED's, etc.

[52 Bill]

I've taken them apart before, but I've never seen one filled with whatever that white gooey stuff is.

I don't think that I've ever seen a bulb burn out in one of these, but I have seen a lot of photocells go bad. In fact there was a late 60's Fender service bulletin about a bad run of cds cells.

In the old days when the replacement "bugs" weren't as readily available as they are today, we used to buy bulk photocell packs and just replace the bad cells. In a pack of 10 assorted cells maybe 5 or 6 were usable and the rest were either too slow in response or too low in off resistance to work well.

I find that the new "bugs" are far superior to the old ones, and will often make even a "good" original one sound weak.

[pontiacpete]

I've taken them apart before, but I've never seen one filled with whatever that white gooey stuff is.

that stuff is some sort of hard epoxy or whatever...
ON this one the light works but the resistor set in the epoxy(?) is open.

[Enzo]

Neon bulbs don't burn out as a rule, but they do darken. A black coating builds up inside the glass. it can sometimes affect operation.

[pontiacpete]

picture of photocell. One lead was loose (tried resoldering, no luck yet)and there's white spot, looks like it's inside. oh well

[Enzo]

Mouser, Jameco, lots of places sell photocells

[pontiacpete]

would I get the 3 ~ 11K like this one?

Digi-Key - PDV-P8001-ND (Manufacturer - PDV-P8001)

[Enzo]

Might work, but the high resistance is only 200k on it. I would prefer a higher off resistance myself.